Cadillac Owners Forum banner

1 - 20 of 47 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter #1
An associate gave me a 2002 Deville with 75k miles Northstar V8. The problem was overheating. It was producing some vapor out of the exhaust so I figured it was the notorious blown head gasket problem. I ran a can of Blue Devil through it and its still overheating. I replaced the thermostat, pulled the water pump cover and it appeared to be ok, flushed the cooling system. pulled the radiator to make sure it wasn't clogged.

I just did another block test. That's the blue stuff in the tube that you hold over the coolant reservoir. It stayed blue. There's no vapor coming from the exhaust, but yet the coolant reservoir still boils over after a few minutes (10-15) of idling time. I checked the return line stem to make sure it wasn't clogged. That's actually the line that's causing the reservoir to boil over.

Does anyone have any ideas before I dispose of this car. It's still got a lot of live in it, but not if it can run without overheating.

There are no coolant leaks anywhere including the water pump. I checked to make sure when I turned the pulley side that the fins turned and they did. Is there anything else about the water pump that could fail?

The larger hose coming from the pump across the radiator does get hot and when very hot seems to have some pressure on it.

It does have a PO410 (secondary air system) code. Any relation to this problem?

Any other diags or things I should be looking at? I hate to get rid of this car if there's something that I'm missing or could try. It's in remarkably good shape for it's 17 years.

Thanks,

Roveer
 

·
Registered
Joined
·
225 Posts
Sounds like an 'air lock' is about the only possible left. Maybe pull the purge line to verify coolant 'movement'/waterpump actually pumping.

I have had much better results using the 'vacuum fill' for coolant. Almost a necessity on cameros/firebirds/vette radiators they're on such a slant, and it makes all fills easy-peasy/almost always purge free.

I would defiantly not throw in the towel on a 75k car in the condition you describe

Also make sure there is good flow/coolant exchange going on in the tank when testing, to get accurate results.
Not saying you didn't, but,,,,i watched a guy test for someone buying a car, and well,,, he was testing the 'overflow tank/bottle'. Was not a caddy, but needless to say there was '0' flow/circulation doing it that way. Everyone was pretty happy till I pointed out how useless testing that way was.

Good Luck on getting it roadworthy.
 

·
Master of the Dark Art of Diagnostics
Joined
·
18,724 Posts
I ran a can of Blue Devil through it and its still overheating.
BIG - HUGE GIGANTIC mistake - that CRAP will only make the problem WORSE! -

all you can do now is check the PURGE LINE for a constant - gentle - coolant flow whenever the engine is running -

if no flow - the most common cause is HOLLOW BOLT that the PURGE LINE attaches to is clogged -

the PURGE LINE is the ONLY way to release trapped air from the cooling system -
trapped air prevents the water pump from moving the coolant through the system -
more proof of trapped air in the system is no heat from the heater -
 

·
Registered
Joined
·
14 Posts
Discussion Starter #4 (Edited)
I ran a can of Blue Devil through it and its still overheating.
BIG - HUGE GIGANTIC mistake - that CRAP will only make the problem WORSE! -

all you can do now is check the PURGE LINE for a constant - gentle - coolant flow whenever the engine is running -

if no flow - the most common cause is HOLLOW BOLT that the PURGE LINE attaches to is clogged -

the PURGE LINE is the ONLY way to release trapped air from the cooling system -
trapped air prevents the water pump from moving the coolant through the system -
more proof of trapped air in the system is no heat from the heater -
Purge line runs clean. I checked the purge line stem originally. I referred to it as the "return line stem" in my original post. It was and is now clear with good flow, then and now.

I will say, heat takes 15 minutes before I feel any and have to be driving the car in order to get any. idling doesn't seem to produce any heat no matter how long I let it idle.

Another odd thing is, the purge tank is boiling over when the temp gauge is only reading half way. That doesn't sound right.

I just read another post about "false boiling". Gist of it was bad HG (notorious on Northstar, or better yet, pulled head bolts), causing exhaust gases into cooling system then venting back to purge tank looking like boiling. Suggestion was to read temp of fluid when it's "boiling" out of purge tank and that will tell the truth.

My guess is exhaust gases in system. If that's the case I'm not spending 3k+ for a the prescribed fix, or a rebuilt engine. Although it does look like an interesting project. I don't have any of the required equipment to do such a job, which among other things requires pulling the engine.

I did re-run block test and towards the end, just before the "boil over" the fluid wasn't as bright blue as it was originally, more of a greenish which is on its way to yellow which tell us that we are likely getting exhaust gases in the coolant.

All of this happening with no steam coming from exhaust.

Roveer
 

·
Master of the Dark Art of Diagnostics
Joined
·
18,724 Posts
Purge line runs clean. I checked the purge line stem originally. I referred to it as the "return line stem" in my original post. It was and is now clear with good flow, then and now.

I will say, heat takes 15 minutes before I feel any and have to be driving the car in order to get any. idling doesn't seem to produce any heat no matter how long I let it idle.

Another odd thing is, the purge tank is boiling over when the temp gauge is only reading half way. That doesn't sound right.

I just read another post about "false boiling". Gist of it was bad HG (notorious on Northstar, or better yet, pulled head bolts), causing exhaust gases into cooling system then venting back to purge tank looking like boiling. Suggestion was to read temp of fluid when it's "boiling" out of purge tank and that will tell the truth.

My guess is exhaust gases in system. If that's the case I'm not spending 3k+ for a the prescribed fix, or a rebuilt engine. Although it does look like an interesting project. I don't have any of the required equipment to do such a job, which among other things requires pulling the engine.

I did re-run block test and towards the end, just before the "boil over" the fluid wasn't as bright blue as it was originally, more of a greenish which is on its way to yellow which tell us that we are likely getting exhaust gases in the coolant.

All of this happening with no steam coming from exhaust.

Roveer
============================
I will say, heat takes 15 minutes before I feel any
and have to be driving the car in order to get any.
idling doesn't seem to produce any heat no matter how long I let it idle.

this is definitely NOT right and could be a clue -
OR it could be totally unrelated to the cooling system -
and strictly an HVAC issue -
possibly as simple as a clogged cabin air temperature sensor fan -

---------------

IF the head gaskets are leaking (due to pulled head bolts) exhaust gasses get pumped into the cooling system -

this is where the PURGE LINE comes in -
it "purges" the air/exhaust gasses from the cooling system and directs it to the SERGE TANK - the ONLY way to get rid of the trapped air -

this is why the BLOCK TEST is the definitive test for failed head gaskets in the Northstar motor - done CORRECTLY - it is 99.9999% infallible -

the blue fluid only reacts to hydrocarbons and changes color -
the higher the concentration - the more dramatic the color change -
lighter blue - clear - green - yellow -

with the PURGE LINE open and functioning -
no color change = no failed head gaskets -
ANY color change = various stages of failed head gaskets -

here are a few other fairly common causes for overheating in no particular order:
slipping water pump belt due to a worn-out belt tensioner -

sticking/stuck thermostat -

faulty SERGE TANK pressure cap -

weak antifreeze mixture - MINIMUM is 50/50 antifreeze/water - I generally run 65/35 -

clogged radiator -

debris on the AC condenser blocking airflow to the radiator -

missing upper and/or lower plastic air deflectors -
 

·
Registered
Joined
·
14 Posts
Discussion Starter #6
============================
I will say, heat takes 15 minutes before I feel any
and have to be driving the car in order to get any.
idling doesn't seem to produce any heat no matter how long I let it idle.

this is definitely NOT right and could be a clue -
OR it could be totally unrelated to the cooling system -
and strictly an HVAC issue -
possibly as simple as a clogged cabin air temperature sensor fan -

---------------

IF the head gaskets are leaking (due to pulled head bolts) exhaust gasses get pumped into the cooling system -

this is where the PURGE LINE comes in -
it "purges" the air/exhaust gasses from the cooling system and directs it to the SERGE TANK - the ONLY way to get rid of the trapped air -

this is why the BLOCK TEST is the definitive test for failed head gaskets in the Northstar motor - done CORRECTLY - it is 99.9999% infallible -

the blue fluid only reacts to hydrocarbons and changes color -
the higher the concentration - the more dramatic the color change -
lighter blue - clear - green - yellow -

with the PURGE LINE open and functioning -
no color change = no failed head gaskets -
ANY color change = various stages of failed head gaskets -

here are a few other fairly common causes for overheating in no particular order:
slipping water pump belt due to a worn-out belt tensioner -

sticking/stuck thermostat -

faulty SERGE TANK pressure cap -

weak antifreeze mixture - MINIMUM is 50/50 antifreeze/water - I generally run 65/35 -

clogged radiator -

debris on the AC condenser blocking airflow to the radiator -

missing upper and/or lower plastic air deflectors -
I've crossed a bunch of those items off the list already.

Tomorrow I'm going to do a few things.

1. plumb the surge tank so I can see where all the pressure is coming from, either the purge line or back up the lower hose. My guess is that it's coming back up the main hose since the effect I see is all the liquid rising up and coming out of the tank.

2. Use my laser temp gun to determine actual temp of fluid when the boiling over thing is happening. This goes back to the "false boiling" I read about.

3. Capture all that boiling over vapor and test it with the block tester. When I do the block test and it starts to boil over I have to stop sniffing because there is fluid all over the place. If I can rig it up so I can continue to capture when the "boiling" is happening then I can see if it's actually exhaust gases escaping through the coolant system. I actually think this is what is happening.

I'll report back.

Roveer
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,322 Posts
After the entire block and heater systems get to full operating temp - 188 - 210 degrees - the upper radiator hose should be HARD and then, as the thermostat opens, HOT. There is NO flow through the radiator until the thermostat, in the lower hose, begins to open. The thermostat begins opening at 188 degrees and is fully open at 206 - HOT!!! - a Northstar with good cooling system runs at 190 - 210 all day, every day.

Surge tank, purge line.

The purge line and the lower surge tank fitting are both on the same cooling system - equal pressures in both. The purge line is designed at the high point of the system so it tends to bleed air and gases back to the airspace in the surge tank. The lower fitting "sits" on the cooling system proper and so should always "see" solid coolant. The surge tank is basically a reservoir for coolant expansion/contraction as it heats/cools. Yes, the purge line flows a bit of coolant into the tank - but the entire system is sealed and pressurized so the net filling effect is zero.
Too bad you installed Blue Devil - big mistake for a Northstar.

Sounds to me like you have one or more airlocks in the system, the water pump is moving NO coolant, and the engine boils over as a result of an overheat hot spot. The "no heat for 15 minutes" thing says the heater core is airbound, receiving only hiccups of warm coolant now and then.

Have you visually inspected the water pump drive system? The safety shroud comes off with two 10mm nuts and a 10mm bolt. The water pump drive pulley, on the intake cam extension, turns at 1/2 engine speed, so the pump pulley is smaller to step up pump speed. The drive pulley has a metal hub TIGHTLY pressed onto the cam extension. Use the correct remove/install tools. The belt tensioner pulley is a common, frequent failure item. $25 at a parts store. The drive pulley hub may still have a black plastic thread protector installed. Torx bit. Cam extension is threaded internally for the install tool.

  1. water pump drive pulleys.gif Pulley and tensioner (Notes).JPG Water crossover assembled.gif Thermostat and cover diagram.gif Water pump tensioner pulley.jpg water pump pulley install.gif
 

·
Super Moderator
Joined
·
86,087 Posts
There's no vapor coming from the exhaust, but yet the coolant reservoir still boils over after a few minutes (10-15) of idling time.
Have you checked the surge tank cap? If it is not sealing and holding pressure, the engine WILL prematurely overheat and boil over.
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,322 Posts
Yes - of course the coolant boils after 15 minutes with no system pressure. Plain water boils at 212 degrees at sea level pressure. 50/50 coolant boils at 226 degrees at sea level pressure - right about where fans should go to SLOW for the pre-2006 Northstar system.

Courtesy of Ranger -

Coolant Boiling point.jpg
 

·
Registered
Joined
·
64 Posts
When I took apart my Northstar the head gaskets were completely plugged at all the small holes beside the siamesed cylinder walls. This would create hot spots, making steam pockets, which makes those areas hotter.......
There was also a large amount of sealant accumulated in the bottom cooling jacket area making it impossible for water to carry heat away from the cylinders in those areas.
Also, there was one completely let go head bolt thread and 3 or 4 others not clamping properly. Gasket had deteriorated significantly as well, meaning that most of the gasket had broken away in the floating cylinder wall area. This makes cooling poor as well, since those covered areas are needed to direct flow all the way along the block, and not just short circuit back out right away, leaving the rear of the engine to get overheated.
When it finally failed big time, the fire ring itself let go and then coolant went ‘everywhere’, making huge clouds of smoke and very rough running. Of course I shut it down right away, at that point.

Point being, the sealant ‘fix’ is only a maker of more problems, not a fix, not even temporarily.

Also possible is the sealant ‘fix’ ‘fixed’ the heater core passages to the point of very little flow.

If you have 15 minutes before it boils over, there should be plenty of time to get a block test done.

Notwithstanding all the above, it appears to me that there is a failed gasket. Failed head bolt thread, actually. Failed gasket is symptom not cause.

Repairing the engine should be an option given the low miles and good condition of the car. (Mine is at 85K)
You need to consider what you could replace it with for the price, and then still not know what condition the engine/car is in. When you do the repair, you know exactly what condition its in, GOOD! Then you can enjoy the car for a long time.

There are various repair options, all well documented on here.

I used ‘Sure Grip’ studs from NORTHSTAR PERFORMANCE. Engine is now ‘bulletproof’.
 

·
Registered
Joined
·
14 Posts
Discussion Starter #11 (Edited)
After the entire block and heater systems get to full operating temp - 188 - 210 degrees - the upper radiator hose should be HARD and then, as the thermostat opens, HOT. There is NO flow through the radiator until the thermostat, in the lower hose, begins to open. The thermostat begins opening at 188 degrees and is fully open at 206 - HOT!!! - a Northstar with good cooling system runs at 190 - 210 all day, every day.

Surge tank, purge line.

The purge line and the lower surge tank fitting are both on the same cooling system - equal pressures in both. The purge line is designed at the high point of the system so it tends to bleed air and gases back to the airspace in the surge tank. The lower fitting "sits" on the cooling system proper and so should always "see" solid coolant. The surge tank is basically a reservoir for coolant expansion/contraction as it heats/cools. Yes, the purge line flows a bit of coolant into the tank - but the entire system is sealed and pressurized so the net filling effect is zero.
Too bad you installed Blue Devil - big mistake for a Northstar.

Sounds to me like you have one or more airlocks in the system, the water pump is moving NO coolant, and the engine boils over as a result of an overheat hot spot. The "no heat for 15 minutes" thing says the heater core is airbound, receiving only hiccups of warm coolant now and then.

Have you visually inspected the water pump drive system? The safety shroud comes off with two 10mm nuts and a 10mm bolt. The water pump drive pulley, on the intake cam extension, turns at 1/2 engine speed, so the pump pulley is smaller to step up pump speed. The drive pulley has a metal hub TIGHTLY pressed onto the cam extension. Use the correct remove/install tools. The belt tensioner pulley is a common, frequent failure item. $25 at a parts store. The drive pulley hub may still have a black plastic thread protector installed. Torx bit. Cam extension is threaded internally for the install tool.
Sub,

Thanks so much for detailed explanation. It was extremely helpful to better understand how the entire system works.

I've inspected the water pump housing and pulley pretty well a few days ago. I removed the shield and watched it operate. The belt is tight and no slipping. I also pulled the pump cover to inspect the pump. It appeared to be in good condition and the fins were connected to the outer pulley and would turn together with no slip. I decided not to replace the pump based on that inspection considering the the fact that I'd have the get the special tool and the additional expense of changing yet another part. I did get and install a new thermostat so I've inspected all those area's closely. It looks like I can disconnect the heater core by removing one of the hoses at the firewall and connecting it to the other to basically remove the core from the loop. I'm wondering if I should do that to eliminate one more item is this puzzle. I really need to determine if I'm going to scrap this car or continue trying to make it roadworthy. With all the known defects having to do with the heads I really don't want to keep pouring weekend after weekend of my time into a lost cause.

Let's see what today brings. I'll report back.

Roveer
 

·
Registered
Joined
·
14 Posts
Discussion Starter #12
When I took apart my Northstar the head gaskets were completely plugged at all the small holes beside the siamesed cylinder walls. This would create hot spots, making steam pockets, which makes those areas hotter.......
There was also a large amount of sealant accumulated in the bottom cooling jacket area making it impossible for water to carry heat away from the cylinders in those areas.
Also, there was one completely let go head bolt thread and 3 or 4 others not clamping properly. Gasket had deteriorated significantly as well, meaning that most of the gasket had broken away in the floating cylinder wall area. This makes cooling poor as well, since those covered areas are needed to direct flow all the way along the block, and not just short circuit back out right away, leaving the rear of the engine to get overheated.
When it finally failed big time, the fire ring itself let go and then coolant went ‘everywhere’, making huge clouds of smoke and very rough running. Of course I shut it down right away, at that point.

Point being, the sealant ‘fix’ is only a maker of more problems, not a fix, not even temporarily.

Also possible is the sealant ‘fix’ ‘fixed’ the heater core passages to the point of very little flow.

If you have 15 minutes before it boils over, there should be plenty of time to get a block test done.

Notwithstanding all the above, it appears to me that there is a failed gasket. Failed head bolt thread, actually. Failed gasket is symptom not cause.

Repairing the engine should be an option given the low miles and good condition of the car. (Mine is at 85K)
You need to consider what you could replace it with for the price, and then still not know what condition the engine/car is in. When you do the repair, you know exactly what condition its in, GOOD! Then you can enjoy the car for a long time.

There are various repair options, all well documented on here.

I used ‘Sure Grip’ studs from NORTHSTAR PERFORMANCE. Engine is now ‘bulletproof’.
Thanks for the information. I'm all over Northstar Performance. Their system is amazing. I would do it in a minute, but I've been watching videos all weekend and the amount of work, tools and experience required are well beyond my ability. I'm hesitant to even talk to my mechanic about this repair since I'm sure he's going to quote me 3k+ for this work. I'm in NJ and this car is not exactly great for our winters. This is going to be a car for my kids and I'm concerned about the next round of break-down's, part failures. It just seems like it could become a sink hole of cost. If I went that route, it would be a good opportunity to discover / fix all those items you mentioned. I'm really of the opinion that this can be rehabilitated to a decent reliable vehicle, but watching some of the NSP videos showed me that once you do the top side, there's always a chance that you could have a failure on the bottom side (similar bolt issue). There's also a possibility that the previous owner drove deep into an overheat situation and there could be warping or cracks. This means that I'm half way into an expensive repair just to find out there's more problems and more expense. I originally told my family members that I didn't want to take the car because of the potential problems, that was before I fully understood the issues with Northstar. Now I'm in a total quandary.

Roveer
 

·
Registered
Joined
·
14 Posts
Discussion Starter #14
I just noticed the radiator cap lower seal is fairly chewed up. Guess for 5 bucks I will get a new one. Can't imagine that this is my problem, rather just one of the many issues.

Roveer
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,322 Posts
"Deep into an overheat situation" - not a problem. The Northstar goes into Camel Mode and was designed to run for 50 miles with NO coolant. Read this - and the rest of it - it was written by one of our members who was a GM Northstar Systems Powertrain Engineer.


Nothing wrong with bypassing the heater core.

If you can, flush the core using a garden hose. BUT you then run the risk of water intrusion at wiring and electrical connectors, so a hose extension jury rig is in order.
 

·
Registered
Joined
·
64 Posts
I can see how you might shy away from this repair. Especially since it was a ‘free’ car. (Those can be the most expensive....) You are not emotionally invested, beyond a tiny bit toward your associate. It’s ok to do what you like, I don’t think you are beholden to him.

I would suggest just passing it along to someone who is well aware of the needed repair and is capable of doing it, whether themselves or at a qualified shop.

I believe I saw a post from Harry Yarnell; check out that option. He is well acquainted with these cars and understands the situation.

Pick your ‘favourite’ ordinary car for your kids. Cadillac is not ordinary nor well suited to the uninitiated. At least not cars going on 20 years old.
 

·
Registered
Joined
·
14 Posts
Discussion Starter #17
You're in Jersey, right? Where in Jersey?
If you decide to 'get rid' of the car, what would you accept?
I can see how you might shy away from this repair. Especially since it was a ‘free’ car. (Those can be the most expensive....) You are not emotionally invested, beyond a tiny bit toward your associate. It’s ok to do what you like, I don’t think you are beholden to him.

I would suggest just passing it along to someone who is well aware of the needed repair and is capable of doing it, whether themselves or at a qualified shop.

I believe I saw a post from Harry Yarnell; check out that option. He is well acquainted with these cars and understands the situation.

Pick your ‘favourite’ ordinary car for your kids. Cadillac is not ordinary nor well suited to the uninitiated. At least not cars going on 20 years old.
Yup, you said it all. Thanks for the advice.

Roveer
 

·
Registered
Joined
·
14 Posts
Discussion Starter #18
So I put the 5 dollar radiator cap on and let it idle up to temp. The heat worked right away, but within 15 minutes the gauge was going up. I also noticed a fair amount of steam out the exhaust as well as steam coming up from the radiator. I noticed the radiator steam the other day but it stopped pretty quickly. I did hose off the radiator from the front of the car (on Sunday) which means I was spraying through the outer radiator (AC?) Is it possible that it's just moisture on the outside? Should I consider a pressure test for the cooling system?

The steam out the exhaust tells me (the uneducated) that the heads/gaskets etc are in bad shape.

Roveer
 

·
Registered
Joined
·
14 Posts
Discussion Starter #19
"Deep into an overheat situation" - not a problem. The Northstar goes into Camel Mode and was designed to run for 50 miles with NO coolant. Read this - and the rest of it - it was written by one of our members who was a GM Northstar Systems Powertrain Engineer.


Nothing wrong with bypassing the heater core.

If you can, flush the core using a garden hose. BUT you then run the risk of water intrusion at wiring and electrical connectors, so a hose extension jury rig is in order.
I just read the "camel mode" link you provided. That's very interesting. I assumed this motor would just eat itself up. I was thinking severly warped and cracked. Since I have no information on what the owners did when they experienced overheating, I have no idea how bad the damage could be.

Roveer
 

·
Super Moderator
Joined
·
86,087 Posts
I also noticed a fair amount of steam out the exhaust as well as steam coming up from the radiator.
Steam from the radiator would indicate an external leak, like a cracked radiator side tank.
Steam from the exhaust would point to a failed HG.
 
1 - 20 of 47 Posts
About this Discussion
46 Replies
15 Participants
Republicrider
Top