View Full Version : Wanted:1999 4.6 NorthStar leak-down values

05-01-06, 05:36 PM
Wanted: 1999 4.6 NorthStar leak-down values

What filtered shop air pressure should be used, 75, 90 or 100 ?

What expected leak percentages (differential gage ) should one expect on a cold engine ?

Wet vs Dry ?

Coolant system is filled for the head gasket check.

05-01-06, 06:11 PM
I assume you are checking for a bad head gasket. Just pump the cylinders up with as much air as you have available, 125-150 psi and watch for bubbles in the cooling system. That is all that is needed.

05-04-06, 08:27 PM
Additional information.
Adding it to all threads I have asked for information in.

Completed the leak down test.
Radiator and all lines were filled.
Used 100 - 125 PSi shop pressure to all cylinders one at a time.
Nothing, no bubbles or anything.

Negative, just like the hydrocarbon test.

also colling system test, holds pressure

Still overheats, coolant leaks out the over flow tube when hot.

what next ? what could be wrong

05-04-06, 08:32 PM
stuck thermostat?

05-04-06, 08:51 PM
I have replaced the thermostat, water pump, cap, flushed and fiilled the system with dex and the tablets.

performed a coolant system pressure test, no loss @ 5+ hrs @ 18 psi, then turned engine over nothing blew from the cylinders.

Tested the cooling system for the presence of Hydrocarbons.
Ran the chemical based test from 130 - 207 degrees, negative results.

Tested all the lines and nothing is clogged.

At a real loss here.

05-04-06, 09:12 PM
Flush the radiator.

05-04-06, 10:00 PM
I will ditto the radiator flush.

05-04-06, 10:54 PM
I sounds like the vapor vent line for the water pump may be plugged for some reason. If the pump cannot vent vapor that accumulates it will "vapor lock" and cause overheating.

At the pressurized surge tank....find the 3/8 hose coming from the engine. Disconnect the hose. Some coolant should flow from the nipple on the surge tank indicating that the nipple is open. This is good. Start the engine. Coolant should flow fairly freely from the hose from the engine. If not, the vapor vent line is plugged and is possibly the problem.

Look at the water pump and water crossover. Specifically by the upper radiator hose. Just by the radiator hose connection to the water crossover there is a fitting with the 3/8 hose on it. That is the vapor vent line. It is actually a hollow bolt that serves to mount the water crossover and vent the system. Take the hose off. Start the engine. Coolant should piss from the nipple/hollow bolt. If not, find out where it is plugged. Start by removing the bolt and inspecting......

I assume the fans are working...???

When the pellets were installed, were they put into the radiator hose itself or did you put them into the surge tank? If they went into the tank the material may have settled in the hose from the tank to the water pump. Make sure it is clear and not clogged. Always install the coolant supplement into one of the main radiator hoses.

Is the cap holding pressure in the system? Even with a new cap there may be a system pressure leak so that the system is not pressurizing. That would cause false boiling and overheating.

What about the water pump drive belt and water pump drive belt tensioner? If the belt is slipping the water pump will not turn adequately and the system will overheat. Check that the tensioner is tensioning the belt and not stuck or jammed with corrosion and that the correct length belt is installed.

05-04-06, 11:25 PM
Here it goes.

Flushed the radiator twice in the past two weeks with prestone flush.
When filled, the pellets were crushed and put into the large radiator hose as coolant was added.

The system was belched (sp) several times to make sure that air pockets did not exist.

At the water pump both of the radiator hoses were checked to make sure that no obstructions existed, by blowing air into them and water via an adapter in both directions.

The 1 inch hose to the pump hosing was removed and tested in a similar fashion. with air and water .

A small 3/4 inch hose from a bolt with a clamp was removed, coolant flowed out of it when removed and air passed into it with out a problem.

Then all the other items were replaced.

Additional observations

This is why I suspected the head gasket. As the engine starts to warm up @ 120 degrees (cold still), it I drive around the large upper radiator hose begins to get firm as if it has air in it (temps still below 150).

As the engine heats up and over heats it gets slightly firmer, but the hoses never expand like they are going to burst.

WOT causes the temps to quicky rise.

It takes a long time to cool down ( 3 + hrs when its 70 degrees outside ).

I can perform a full leak down test next week instead of the abbreviated test where shop air is pumped in and controlled with a single regulator, may not show anything else.

I know the abbreviated test is working, a breaker bar must be used to hold the engine at the crank during the test. Often I had to use my leg and one hand/arm to hold the bar when shop air at the full pressure was added. When done, with a careful rotation one could easily hear the air rapidly pass the valves.

The belt for the water pump and pully are tight but do not turn at a very high rpm to me.

Have watched both of the front fans turning.

Stumped !!

Loose screw
05-05-06, 01:40 AM
Just a couple thoughts

Loosen radiator cap - let system breath and see if that changes the over heating under WOT

With other engines - If air is getting past the head gaskets into the cooling system it can fill the top of the cooling jacket in the block and the top of the cylinders will be dry and not cooled and heat will be stored up but what can really cause the over heating is that the thermostate can not get hot enought to open until there is a ton of heat stored in the engine but once it does open both gases and coolant will rush out and the coolant entering the jacket get super heated very fast - the engine will experience and unsteady cooling cycle with great extreams - very poor cooling and overheating and once warm difficult to cool down even at idle and the cooling fans running. I am assuming the same occurs with the N*

If it is a head gasket pull a couple plug wires at a time and then WOT and observe cooling system performance - if it is the head gasket, on those cylinders with the spark plugwire pulled, the lack of the normal very high increase in presure that occurs with ignition in that cylinder will no longer occure or will the leak of gases, it will make a big difference in how much gas and or coolant will leak in and out of the cylinder. This can also help to locate were the leak is, if any.

But aside from that, I would be checking the exhaust, I had an engine that had a blockage but only after it would heat up or under WOT, a plate in the muffler had broken a couple welds and would flex under load and largely seal off the passages. The same condition could occure in a cat. Since you have done a compressed air test on the cyclinders and got no leaks (you would need a pretty big leak to get the over heating you discribe) I assume you have two mufflers, I suspect a bad cat, if you also have reduced performance a WOT and high RPMs while the engine is still cool, I would put money on it. If performance is still good at high RPMs I would continue checking the head gasket.

You do still have the skirting under the radiator and front of the engine? It is very important to prevent air that has gone throught the radiator and is hot from recirculating repeatedly through the radiator repeatedly and helps with overall air flow.

This one is a little more unlikely - park next to another N* and open the hoods and see if each cooling fan appear to work the same. I had a Buick that the primary fan was working but not as hard as it was susposto (it was hard to tell). I eventually replaced it and the problem was solved. When driving at 55+ and no load does it still over heat?

05-05-06, 07:17 AM
The car can be driven around at low rpm's for 30 minutes and the temps stay around 203.
When the rpm's get above 2200 the temperature seems to increase quickly.
The problem was noticed when taken on a trip to the mountains.

Is there sone way that a northstar could have been installed incorrectly that can cause this problem.

Searching through some papers that the PO left in the car regular service records from a dealer were found up to 2/3003. Then on 10/2003 there is a freight slip for 500 lbs, after a few receipts for service at the place where the freight was delivered. From what I can determine, that was 8K to 9K miles ago.

Do not know the PO or if the freight slip was for this car, all the papers have the same contact name before the freight slip, the slip and after.

It does not have starting or driveability issues, like if a 300hp was used and not a 275hp. Examination of the cradle and dents on it, compared to the condition of the car are not consistant.

Still confused.

05-05-06, 09:54 AM
Called the PO and the installer of the engine.

A reman engine from Go Engines in Lansing IL, was installed less than 15K miles ago. The PO purchased a long block from them. It arrived on a pallet, shrink wrapped and looked like new.

That is where I am at now.

Will poor or non permium fuel cause over heating ?

Probably purchased on ebay, go engines @ 18328 Oakley Ave Lansing is in a residential neighborhood.
The telephone number has been changed.

05-05-06, 10:25 AM
Called the PO and the installer of the engine.

A reman engine from Go Engines in Lansing IL, was installed less than 15K miles ago. The PO purchased a long block from them. It arrived on a pallet, shrink wrapped and looked like new.

That is where I am at now.

Will poor or non permium fuel cause over heating ?
No, It will have no effect.

Loose screw
05-05-06, 12:11 PM
How is the power at high RPMs ?
How does it idle, is it smooth or rough and miss ?

05-05-06, 12:47 PM
Just put everything back together after the leak down test.

Drove the car less than one mile to work, engine temp is at 125 degrees.
Opened the hood, upper radiator is full looking.
Turned the radiator cap and the system is pressurized.

Smelled the air/gas/??? coming from the coolant tank, its very foamy
does not smell like gas or exhaust. The coolant coming out is overflow is cold.

05-05-06, 06:36 PM
Engine runs smooth all through the power curve.
Pulls very hard even from a stop @ WOT.
Does not miss.

Sometimes you bet a quick pop from the throat when starting it.

At times I think the water pump is churning up the coolant and creating the foam and pressurizing the cooling system.

05-05-06, 08:15 PM
someone had a problem with putting the crushed up tablets in the (upper/lower) hose. Apparently it ran straight into the thermostat and clogged it up. I don't think it's necessary to crush them.

05-06-06, 12:14 AM
I will drain it and pull the thermostat tomorrow.

All suggestions.thoughts are appreciated.

Loose screw
05-06-06, 01:52 AM
That foaming of the coolant is very interesting and very unusual, I would agree that the water pump may be reworking the same coolant over and over. Your certainly have tested the head gaskets fully

A blocked thermostate is likely or a colapsing lower hose which would only occure at mid to high RPMs and when the thermostate has warmed and is well opened. Easy to test for. So - with the engine good and hot (thermostae wide open), race the engine while looking at the lower radiator hose - does it colaps (this can occure even in a well pressurized system) The water pump can try to draw more coolant in then the hose can handle and the hose with colaps flat and seriously reduce coolant flow. On some engines a large wire spring is installed inside to keep the hose fully open under all conditions. Frequent high RPMs can help a weak hose eventually to flex and then colaps more and more each time. The higher temperatures also make the walls of the hose more flexible and easy to colaps and fold together. Use a bright flash light and examine the full length of the lower hose while runnning the engine at high RPMS, it may take it a few seconds to colaps - if it does.

05-06-06, 11:56 AM
Pulled the thermostat, made no difference, till pressurized very quickly and foamy.

Is the upper radiator hose supposed to run across the from of the radiator ?
It goes from the engine outlet on the drivers side to the radiator connector on the passengers side.

Double checked, the system pressurizes very quickly before the radiator heats up.

Can warm it up without the cap, without water running out, a few bubbles came up and the level dropped very slightly so more fluid was added. Without the cap it warms up to 150 and higher without a problem at idle. I cannot smell fuel or exhaust in or near the coolant tank.

Can a head gasket leak from the combined forces of all the cylinders and not just a single one.

During the leakdown test nothing leaked into the coolant system, no bubbles or anything. We had to hold the crank bolt using a breaker bar to keep it from spinning for all the cylinders.

Can the intake or exhaust manifold somehow leak into the coolant system ?

05-06-06, 12:27 PM
When it's nice and hot, hold your hand on the radiator (from the front if possible, don't want any fingers going AWOL because of the fan(s)). Are there any warm or cold spots?

You should have a really hot core on one side, and slightly less hot on the other side, with no warm or cold spots anywhere. Careful not to burn yourself.

Loose screw
05-06-06, 04:39 PM
That foaming is not normal, has your car been recently bit by a racoon or mad dog - if it is rabies you may have to put it down.

Seriously - loosen the radiator cap (leave it on, just loose so it will allow any presure and gases to vent out) and drive the car, does it still over heat the same? You will have to do this where you won't be in stop and go traffic as the fans may not kick in soon enough. If the car still over heats with the thermostate out and the cap loose - forget about the heads or cylinders leaking the problem is elsewhere, believe your tests.

When you said you flushed the radiator I am assuming you BACK FLUSHED it and observed good flow. Did you do it yourself? A flush or even a super flush chemical is much weaker than a radiator cleaner. :stirpot: Prestone makes a cleaner (a little hard to find too) that is a two part treatmeant, the pros (radiator shops) will also use a cleaner which disoloves deposits and then back flush with high volume and presure water and then repeat until all the tubes flow free. If your cooling system has had the right antifreeze and it has been changed every few years and you have only filled it with distilled water (instead of tap water wihich is full of the building blocks of deposits) it is very unlike you have a plugged or restricked radiator. Radiator flushes will leave a foaming reidue like a soap. But cleaners, which are acidic have to be nutalized and flushed out thoughly. I would not use one on a radiator that it still on N* car but would remove the raditor first. I don't want acid attacking the head gasket or other parts. A flush solution is not going to hurt anything, but it's not going to do much either, (people can't win law suits if they can't show the product is strong enough to damage a part) they are designed to be used every year or two by Do It Yourselfers to just fluch out the old and take off any slim built up - but not do a thing to hard deposits. Cleaners are for people who now how to read and follow directions carefully and have the right safety equipment and experience. You can find the stuff at only some parts stores but you will have to ask for it, it maybe behind the counter. or take your radiator to a radiator shop $35-$75 and they will check it for leaks and fix them too - well worth it as the radiator can get presurized pretty high during the process. The fill with Dexcool and distilled water

05-08-06, 05:15 PM
Flushed the coolant my self using prestone flush.

Tested the system with a full coolant tank, cap loose.

Drove it around, temps reached 230 mark, upper hose was stiff/hard, coolant was steaming/coming from the tank with the cap loosened.

05-08-06, 09:32 PM
Redo the combustion byproduct test. preferably at a radiator shop. They are usually cheaper and they do it more so they are experienced.

You could but the kit youself. It's about $50 at NAPA and it's good for a bunch of tests.

It sure acts like head gaskets but it's odd that you aren't getting bubbles when you pressurize it.

If you crank the engine with the cap off do you see coolant movement in the surge tank?

05-08-06, 10:02 PM
If the engine is cranked with the cap off, little movement if any is seen.
What movement seen is from the car moving.

With the engine @ idle, after a few minutes the level in the coolant tank may or maynot slightly lower and raise a few times until the system heats up, no bubbles have been seen. Then again as it heats up, I usually tend to stand back a bit in case it all of a sudden blows out, never has.

This has been a very interesting experience and since I am a first time "V" class engine owner I am starting to wonder about these cars. I usually avoid dealers but maybe one cannot with a cadillac, my 03 envoy is regularly serviced for all but oil changes at the local cadillac/gmc dealer since its also a pain.

Loose screw
05-09-06, 12:04 AM
Flushed the coolant my self using prestone flush.

Tested the system with a full coolant tank, cap loose.

Drove it around, temps reached 230 mark, upper hose was stiff/hard, coolant was steaming/coming from the tank with the cap loosened.

Ok there you are, do you see what you said - if yourstatement above is accurate "upper hose was stiff/hard ... cap loosened" the upper hose was under pressure with the cap loose! The water pump drives the coolant into the block from the loower hose (I believe) and the so the upper hose is the exit and the way any pressure exits is through the radiator and then back to the engine and release to the tank. If the radiator is plugged or restricked the pressure will build up, it can't get through the radiator fast enough and and the same is true of the heat. And when you flushed the radiator you may have broken loose some crude and deposites and they could have even plugged your radiator up even more, geeting stuck in those tube that were partially blocked. Your upper hose should not be tight, plump and certainly not siff and hard wene ever the cap is off.

Easy test - with the cap loose and engine warm and idleing rev the engine while watching the upper hose - if it looks like the hose is experiencing much more pressure (some is normal) as the RPMs increase you have a plugged radiator - touch it all over as was mentioned by some one earlier and you may find spots that are not hot (plugged) but you will only be feeling the front layer and not the ones behind and you want them all flowing freely and getting the heat out..

You could take off both the top and bottom hoses and get your garden hose and your neighboors hose and stick them in the top hose and turn them on full (do not plug or seal either end). It is a big radiator and most of the water from both hoses should make it out the bottom hose - if not, it is time to take it to a radiator shop your plugged! You need your radiator cleaned, not flushed.

You cold try back flowing it (stick both hose in lower radiator hose and try to hold some of the presure but not all in with a rag) and make the water go through the raiator backwards. Changes directions several times and then recheck for good flow in proper direction. Personally if you can't find the two part radiator clean to desolove all the deposits and crud, your radiator is probably now so plugged - having use the weak flush product that only a professional with their equipment can save it. If it demonstrates it is restricted (virtually never are all the tube pluged). And it is strange that a 1999 is plugged all ready - but hard water and poor matiance of the anitfreeze can do it in just a couple years. Many radiator shops will test your flow rate for free - if you have it out of the car.

05-09-06, 07:11 AM
The radiator outlet hose cannot crush/cavitate; it has a spring wire insert in it.

The PO had the cooling system worked on.
Examination of the radiator makes me think itís not right.
Cooling connectors go to a side tank on the driverís side.
The passenger side of the radiator has a side tank but nothing connects to it.

The outlet of the radiator on the driverís side is below a brake control module. So low that the hose to the water pump must contact the module and rest on its edge in order to be connected it.

Loose screw
05-09-06, 08:52 AM
Oh now the dirty liitle key information is revealed - man what were you thinking :tisk: - tell us up front that the cooling system has been modified. Now things are making sense - your cooling system is all screwed up! How could you have the cap loose then if it is down lower than the top of the radiator like that, and lower than the heads? How can the system properly vent. Did the heater even work, I bet it was disconnected too. Air was probably trapped in several places.

The cooling system as designed by the factory works very well, it needs no extra parts. In any case - start from scratch take out all the added junk on the driver's side, the only things there that belong are the water pump, the 2 main hoses and that little hose connected to the bolt and the return tube to the black tank. On the passenger side should be the black tank and the heater hose assembly. Go to a junk yard or someplace where you can carefully compare car parts to see what you need to keep and remove and what you need to get that the PO modified, damaged or didn't repair. Also get that radiator to a good radiator shop and fix this problem completely and certainly. Do it once, do it right, fix the real problem - restore it to original factory arrangment - you won't be sorry you did.

05-09-06, 11:23 AM
Only the PO know sthe history of the car.

I have not given up yet !


I now know they paid over $20K with 50K miles on it a few years ago, overheated the engine that was in the car and trashed it. Had a remanufactured long block installed around 8/2003. Put maybe 8K miles on the car driving it in town only. Put it up for sale where they live in local papers 9 months ago and on an assignment lot, never sold. They put it up for sale on craigslist where my son saw it. He tried it, liked it and now I have it about 900 miles later. When purchased, the PO said the engine was in excellent condition, never had a head gasket problem, sure its a reman engine. Other than that they said it was in excellent condition. I now believe they were tired of screwing around with it and my son was the next sucker in line.


I do not know if it has been modified or anything, I do not know what it supposed to look like, first cadillac of any kind.

I asked the PO about the engine, in few posts back, they told me a long block was installed. Asked more questions and they told me the coolant system had a leak and they had it repaired. PO thought the radiator was replaced. PO so far has not told me the shop name, maybe it was not a shop, the long block has been verified.

Heater works fine.

Radiator is in the stock position from what I can see.

I question the location of the radiator outlet in relation to the picture in a haynes manual.

In the haynes manual the outlet is higher up, maybe just slightly above the center line of the fans.

On this 1999 the outlet is lower, near the bottom of the fans.

I really question the output hose touching/resting on a brake control module.

Have been to the dealer looking for another car to check out, no luck.

If the transmission cooler lines are removed from the plastic tank on drivers side of the radiator, where should they be connected. It does not have an indivisual transmission cooler. Why does the radiator have a tank on the passenger side with out any hoses attached ?

I need someone with a 1999 Deville and "Y" NorthStar to check the location of the lower radiator hose in relation to the brake unit below it.

The cooling system could be correct, plain and simply, I do not know.

I have ordered my own chemical based tester to perform another hydrocarbon test this week. It was the only test that I did not perform myself, farmed this one out.

Just want everyone on the board to know that I appreciate any and all information in an effort to solve and track down this problem. Although I do not like problems like this one, they can keep our minds sharp !

05-09-06, 03:12 PM
Do you have access to a digital camera? Post a pic to clear our minds.

Loose Screw, good catch on the radiator cap off/stiff upper hose.

05-09-06, 05:37 PM
The first thing you should do is throw that Haynes manual away and get a '99 FSM.

Loose screw
05-09-06, 08:55 PM
OOOOOOPS! :thehand: I may have miss understood your post about the outlet/ radiator cap location and was making assumptions :worship: that your system had been modified and additional part had been added and were resting on the brake unit.

Let see if we are on the same page. The stock cooling system (atleast on my 94 Concours) has an inlet on the radiator's top passaenger side. The out let port is on the drivers side a few inches up from the bottom and under it, is the transmission cooling connections. The outlet hose travels above the anti-lock brake unit but nothing should be resting on it. The lower (outlet) hose also is under the air filter and attaches directly to the water pump. There is nothing connected inline in the lower or upper hoses. They are rather clean designs. The only user opening to the cooling system is at the black tank on the passenger side and heater hoses are located there conected to the underside of the tank. Also that small vent or circulation hose that comes from the throttle body and a small hose from the body to the hollow bolt. That is about it except for the heater tube hose and tubes near the heads on the throttle body side of the engine. I will see if I can find another picture for you. But from what I have seen the cooling system has NOT had any significant changes over the years - it works so good - if the radiator is not restricted.

If I was confused or not about what you have as a cooling system under the hood of your car the fact remains - with the cap loose or off the upper hose should never get stiff/hard or pressurized. The radiator is not designed to restrict flow and cause that hose to enlarge and the bottom hose should never colaps at any RPM or engine temperature. A plugged or restricted radiator can cause either condition which is certain to cause (but not ceratin to be your cause) over heating problems you discribe. Getting your radiator professionally cleaned is something the previous owner(s) OP no doubt didn't do and when the engine was replaced the standard procedure would have been to add the stop leak and if any of the tube were resticted they could have been easily plugged off completely by the stop leak and who knows how many time stop leak has been added to the cooling system - right? The PO could have thought they had a leak problem when the replaced the engine and stop leak could have been added by several different people at different times. And it is put in all at once and in a cold engine in the lower hose to make sure it is broken up before it reaches the radiator. A clean free flowing radiator will not get blocked by the stop leak and so the factory loves it. But ANYTIME an engine - any engine is overhaualed the radiator must be checked for large volume free flow and should be back flushed along with the heater core. If the engine has many miles and or either the heater core or the radiator shows any signs of restriction OR DEPOSITES (use flash light and a small mirror) do not fail to use a two part cleaner or get the radiator professionally cleaned and service and checked for leaks. Again most shops will check your radiator's flow for free while you stand their and watch - that is how they prove to you need their service. And $35-$75 is low cost insurance to protect your expensive engine investment and also avoid overheating and breaking down and a tow bill. A radiator flush is not a radiator cleaning and a pressuresized back flush/flow really get out an amazing amount of crud and deposits - all you have to do is watch them do it once and see the difference it makes - and that difference translates int heat that can't get out of your engine and if the water stays in the engine to long it will vaporize before it can get out and when it does that (because it expands so much) no new water can get in and the problem just get worse. A restricted radiator creates a multitude of problems that can not be compensated with increased air through the radiator or in any other way (turning on the heater will only but only take out about 10-15 % of the heat and may get you through cool weather but warmer weather it will just not even be close to helping enough). A clean raditor is critical to an engines operation and long life yet it is probably the most neglected and improperly serviced part of the engine. Do not fill with tap or filtered water (excep in an emergency - then removes as soon as possible) always use distilled water and the proper antifreeze. Do not wait to change it evey 5 years, every 2-3 years if you plan on keeping your car for a many years.

It certainly would explan why pulling the thermostat made no difference doesn't it. The most restrictive part in your cooling system when it was warm was not the thermostat it is you plugged radiator. And it explains why the upper hose fills, tightens, becomes stiff even with the cap off. It gets tighter with RPM dosen't it?

05-09-06, 09:07 PM
I have two pictures

The radiator hose contacting the brake module.
Position of the lower hose where it enters the radiator.

The hose sets stiff quicker with higher rpm's.
I do not know if the car has the correct radiator, based on the contact with the brake module.

Talked with my son, when it overheats the brakes are also affected, they shudder when the pedal is pressed.

The PO had recipts for a brake job in the glove box also.

05-09-06, 09:12 PM
That does not look right. It is bound to waer through and I cannot imagine the factory building it like that.

Loose screw
05-09-06, 11:03 PM
The hose looks like a aftermarket preformed hose (that may fit several applications) as such the hose ends many times need to be trimed for a good fit in this case the radiator end of the hose should be trimed which would move the whole hose towards the radiator and away from the brake unit. But someone may have installed the hose and the trimed it at the other end or not at all. Also the hose may not have been made with a sharp enough turn to correctly fit into the space with out touching. The hose needs a very short straight section that fits on the radiator outlet and then imediately start the turn.

Since you are going to take the raiator out (right?) to get it cleaned it would be the perfect time to take that hose to a dealers part counter and compare it to the factory one.

Loose screw
05-09-06, 11:16 PM
Could you please explain your statement:

"Cooling connectors go to a side tank on the driverís side.."

The only tank that should be on the drivers side is the window washer tank at least on my 94 and other year models I can remember.

The pictures of the radiator show that it appears to be the correct radiator. The hose is wrong

05-10-06, 08:21 AM
The tanks are attached to the sides of the radiator.

Drivers side one has the transmission cooler lines, the passenger side does not have any connectors attached to it.

Would the correct radiator with side tanks not have connectors to both tanks ?

05-10-06, 11:27 AM
I just checked the FSM for my daughters '99. The radiator appears to have oil cooler lines on the side tank (passenger side) and no trans cooler lines on the drivers side. There may be a small trans cooler in front of the condensor (not positive).

05-10-06, 12:05 PM
My 95 Eldo has the trans cooler lines on the drivers side. Nothing on the pass side.

Loose screw
05-10-06, 07:27 PM
Ok here a a few picture of the correct radiator you will see it is like yours. On the 94 there were no engine oil cool connections as you see on the right side under the inlet tube. But this radiator will work on any year concours. I do not know what year they added the oil cooler connections. But I will probably check and getting the extra plumbing and add it to mine.

For those not familar how this works - The oil and coolant never mix - oil goes into the radiator in chanmer or tubing inside the coolant end cap and is cooled or you might also say warmed on a cold day as flows into the inlet tube which receives the hotest coolant from the engine, this is before it get cooled through the radiator - the transmissions cooler is located on the left it is the divers side and gets the coolest coolant, the coolant that has gone through the radiator.

Notice the angles and locations of the inlet and outlet tubes - just like yours. I paid $135 for this NEW one - shop arround becuse prices vary widely.

I did find out that if your radiator is old and has lost of miles, that the radiator guys say that they are very likely to leak near the inlet tube. There is a small section of the crimping bracket that hold on the plastic end that compresses the gasket under it that does not get crimped dues to the inlet area design but they say when they leak 95% of the time it is there. And GM has not fixed the design. They say that the rapid changing of temperature of that area and it being the hotest spot on the radiator being the intel, causes the gasket to get hard there much sooner and with out the crimping pressure their it is almost designed to fail earlier than necessary. And onec it start to leak there (because of the flexing movement) doesn't really reseal well again.

In addition if you the take the end off to replace the gasket with a nice new soft one - the metal crimping bracket which has to be bent back to get the end off and then recrimped is much weaker than new and 50% of the time will soon leak again as it flexes under the pressure. So if it is only a few years old and less that 100,000 miles go ahead and get it serviced but if it if over that just get a new one - that was from a guy who didn't have new one to sale and would have put a new gasket in if I wanted.

Also the tubes on these radiator are very small (makes then eficent) can get plugged with stop leak very very easily.

Loose screw
05-10-06, 07:34 PM
Here is one more of the drivers side and transmision cooler coonections

05-11-06, 09:53 AM
Appreciate the pictures, looks like same exact radiator with the coolant tanks attached to the sides. The 99 deville we have does not use the passenger side , side coolant tank.

I ordered a new one yesterday, price was higher then you listed, 157 + 10 shipping.

Only hope that the overheating experienced by the northstar has not caused any problems.

A quick chemical test will be performed on the coolant before the new radiator is installed along with a new outlet hose.

05-11-06, 10:59 AM
The end tanks are easily removeable by just unbending the tabs with pliers. Take them off and see what the radiator looks like inside for curiosity.

Loose screw
05-11-06, 12:36 PM
Under pressure carfully check the shaft side of the water pump for signs of leakage both with the engine running and off. A small inspection mirror helps, or look at it from under the car (always block the wheels and parking brake on of course). With as much overheat as you describe you probably had to run it a few times on just water - that can cause the water pump shaft seal to wear out in just a few miles. Not to mention that an overheating engine may not even keep enough water in the water pump to keep the seal wet with even water. Always turn off a overheating engine as soon as possible or just plain on replacing the pump. Antifreeze helps to lubricate the seals on water pumps. Steam will realy clean all lubricant off and out of it and if the steam gets to the bearings and heats and drys them out they will only last a week or two longer any way - at least that has been my :thepan: expereience.

got my brand new raidator here: they have more and yes they ship.
1998 Radiator Cadillac DeVille NEW IN BOX, 1482 PERF$135Labrum Auto Wrecking (http://www.labrumautowrecking.com/) USA-UT(Salt-Lake City)
Request_Quote (http://car-part.com/cgi-bin/quoteForm.cgi?type=g&sEmail=parts@LabrumAutoWrecking.com&email=&part=Radiator&dbPart=675.1&dbSubPart=&model=Cadillac%20DeVille&dbModel=13.1&year=1998&stockNum=PERF&price=135&desc=NEW%20IN%20BOX%2C%201482&name=Labrum%20Auto%20Wrecking&url=http://www.LabrumAutoWrecking.com&int=-1&broker=0&recycler=0&selleruserid=2879&miles=-1&condition=-1&userid=1000&uIMS=&seqNum=143243057&userClaim=&userLang=&userZip=84088) 1-888-522-7862 Request_Insurance_Quote (http://car-part.com/cgi-bin/quoteForm.cgi?type=i&sEmail=parts@LabrumAutoWrecking.com&email=&part=Radiator&dbPart=675.1&dbSubPart=&model=Cadillac%20DeVille&dbModel=13.1&year=1998&stockNum=PERF&price=135&desc=NEW%20IN%20BOX%2C%201482&name=Labrum%20Auto%20Wrecking&url=http://www.LabrumAutoWrecking.com&int=-1&broker=0&recycler=0&selleruserid=2879&miles=-1&condition=-1&userid=1000&uIMS=&seqNum=143243057&userClaim=&userLang=&userZip=84088)

this link is very good for finding parts: http://car-part.com/index.htm you can look in regions or individual states and even show the ones closet to you and/or by lowest price. :thumbsup:

05-11-06, 09:53 PM
Have replaced, water pump, thermostat, cap and DEX now < 120 Miles ago.
I hope the hard parts are still good.
The DEX is trash, its now over dilluted.

:) Tested it with the Lisle 75500 Combustion Leak Detector tonight, it passed.

The $157+ship, Modine 1R2368 (432386) arrived today.
Ordered the OEM lower hose that needs replacement from NAPA.

Should have everything back together over the weekend for another test.

Loose screw
05-12-06, 12:48 AM
The end tanks are easily removeable by just unbending the tabs with pliers. Take them off and see what the radiator looks like inside for curiosity.

That is what I thought until I tried it on my 94 with 150,000 miles on it - the tabs were very rigid and didn't want to bend at all. I was afraid I would damage the end tank or the tabs so I took it to the pros who I thought would use special and better tools to do it. One quoted $60 to take off and gasket the inlet end tank andclean the tubes out, and another $75

I ended up bying a new one for $135 instead

05-13-06, 01:48 PM
The 1999 is back together and ready for testing.

Purchased a NAPA lower hose, it does not contact/rest on the brake module.
Did not come with a spring inside, so i reused the old one.

The old radiator had some gelatinous substance inside it at the lower hose, maybe 1/8 thick in a few places that my finger could touch.

What temperature should the Northstar in a 1999 average with gentle rolling hills ( 10 - 150 feet elevation change) and the air conditioner @ 70 ?

05-13-06, 04:09 PM
Went for a test drive, the temperature went up to 216 when I left it sitting. Once back on the road it dropped to 210, had the air set to 60 degrees in the car.

05-13-06, 04:26 PM
There is nothing wrong with your car. 216 degrees is normal. the thermostat begins to open at 195 degrees and does not fully open until 213 degrees. I think you are chasing a problem that does not exist.

05-13-06, 09:12 PM
There is nothing wrong with your car. 216 degrees is normal. the thermostat begins to open at 195 degrees and does not fully open until 213 degrees. I think you are chasing a problem that does not exist.

No, I think he just fixed it. ;)

er... did you replace the radiator or not? I'm getting lost in this thread.

Loose screw
05-13-06, 10:44 PM
It sounds like you have found the problem(s) :thumbsup:

With those temperatures I assume you have put the thermostat back in, right?

Does the upper hose behave differnetly than what you mentioned before?

I choose NOT to add stop leak at this time - no problem, no need, I can always do it later if needed. If parts are put together right the first time (carefully apply sealers to gaskets) it shouldn't be needed. And of course if a hose start to leak I do know how to use a screw driver to tighten the clamp or repalce the hose. I just don't see the need out justifying the risks of using stop leaks in the coolant system particularly if it's a used engine that probaly has had the treatment and may have some residue in it.

05-13-06, 10:53 PM

The radiator was replaced.

When it first overheated at the start is the the PO was not talking. The vehicle's history was unknown to us. Sso we started looking at the head after the PO told us they had the cooling system worked on.

The head was taken out of the picture after a leak down test and chemical test. When we contacted the PO after finding a freight receipt for an engine in the car, I was old reman long block was out in < 10K miles ago. The PO overheated the engine in the car and messed up the head gasket.

Based on past history, it was good to perform the non evasive engine tests, the PO could have messed this one up like the last one.

When the car is hot it still smells like coolant, but nothing is leaking out below. The smell can be caused by from the past coolant leaking all over everything.

05-17-06, 10:37 PM

The radiator did not solve the problem.

With the new radiator, temps are hitting a maximum of 217 degrees and then cooling down to around 207.

Coolant is still being lost thru the coolant tanks overflow tube.

Seems like it is loosing about 1/2 gallon in 200 miles.

It never leaves a puddle or anything, In fact I have not seen it dripping but the end and inside of the hose are wet.

Checked the other hose connections and they are not leaking.

Loose screw
05-17-06, 11:40 PM

What about the pressure cap? If it lets the pressure out too soon the coolant in the hottest spots could be hot enough to boil which will create poor coolant flow and more steam continously and will increase pressure and continue to cause collant to escape. Cheap part to change out, and easy to eliminate as a possible cause.

Wouldn't that be a kicker in the head if that was the real problem. Acurate pressure control is critical to the system.

Presure caps do get damages with time and too many over heatings - I would think you would want to replace it anyway by now with all it has gone through - if you haven't already.

What are we missing? Hmmmmm....

Could the throttle body be leaking into the intake while under pressure from a crack, I would think that would cause hard starting and steam for a couple minutes after you parked for a while. Hmmmm....

05-19-06, 04:09 PM
The radiator cap was replaced about 500 miles ago.

Since replacing the radiator the temperature is running lower and I can no longer hear coolant boiling in the coolant tank.

The cap was not replaced when the radiator was replaced, that is a thought.

Drove it last night, when at home it the car smelled like dexcol. With a flashlight I could see moisture on the unibody from the engine to the back door on the passenger side. It could be from the cooling system or air conditioner.

Wnat I need is a cap that can report the pressure inside the system.

STS 310
05-19-06, 07:06 PM
someone had a problem with putting the crushed up tablets in the (upper/lower) hose. Apparently it ran straight into the thermostat and clogged it up. I don't think it's necessary to crush them.

That was me. Very bad Idea. Put 3 crushed tablets in the upper hose. Fouled the T-Stat and actually the radiator. Sitting in regular traffic, I overheated rather quickley. The pellets are supposed to disolve on their own for proper circulation. I would check that T stat. You may be pleasently surprised and relieved.

Loose screw
05-20-06, 08:56 AM
Try your local auto part store tool rental they may have a pressure tester to test for coolant system leaks and a tester for the cap too but look at the 2 gaskets of the cap for deformity, warpage and enlagerment. I hav seen where the steam has change their sze and shape If there is none that doesn't mean the cap is sure to still be good as the spring could be weak but if you can see something, buy a new cap. Also make sure there is no stop leak or anythin else enbeded in the gasket or in the sealing surfaces of the mouth of the tank that will cause a leak. In any case at least test out another cap (swap with another car) and see if there is any difference. Some caps do have different PSI ratings, make sure it's rating matches the spec for that cooling system and the correct size. In short make sure you have the exact cap for your system - of course. It is easy to be close and still be wrong.

A pressure leak anywhere in the system will lower the boiling point of the coolant and result in coolant coming out of the cap even if the cap is good.