: Northstar leaking coolant....big time!



Destroyer
11-15-06, 11:36 AM
My wifes '98 Deville is having a problem and for the life of me I cant figure out what is wrong. First of all it runs hot, gets up to 238 degrees. Its been leaking coolant and I have not had a chance to check into it until today, I've just been adding coolant. Yesterday I added some stop leak as well. So today I look under the car and see signs of coolant but small drips. I figured I'd just take it for a spin and get the car up to temp. Got it upto 238 degrees, went home and put it in the garage so I can see where we are loosing all this coolant. I look and clearly see its coming from the overflow hose connected to the radiator right by the cap. So I turn the motor on again with the hood up and its spraying out the hose like a gusher!. When I rev it, it srays even harder. Any ideas here? I'm thinking maybe T-stat (at least thats what I hope it is). The car will not be driven till I figure this out. Thanks for any help.

BTW: the coolant and the oil are not mixing and there is no white smoke out the tailpipe. Someone please tell me its not a head gasket!.

Dadillac
11-15-06, 11:47 AM
I would begin by getting a new AC Delco thermostat and radiator cap. I would bet that one of them is shot.

Don

Destroyer
11-15-06, 12:00 PM
Where exactly is the T-stat on a Northstar?. Thanks. :confused:

Ranger
11-15-06, 02:54 PM
Follow the lower radiator hose to the engine. That is where the thermostat is. That said, the fact that the more you rev it the harder is sprays, sounds like the cooling system is being pressurized with exhaust gasses, meaning a bad head gasket, but I'd certainly eliminate the cap & stat first.

codewize
11-15-06, 03:13 PM
You should also know that the N* is designed to never mix coolant and oil no matter what. It's not like the old days.

They can mix but only under extreme conditions so your finding of no mixing doesn't tell you anything. The fact that is sprays harder when revving IS a sign of exhaust pressurising the system through a bad gasket.

I don't know what the tell tail signs of a stat are on the N* but I think it';s a head gasket from your description.

Destroyer
11-15-06, 04:13 PM
Well, about 3 or so months ago I had the water pump replaced because of a coolant leak and at that time they replaced the t stat as well and all the hoses/belts, etc. How much would it cost to get the head gasket fixed (rough estimate)?. How hard is it to replace the whole motor?. I've done many engine swaps over the years but nothing like this. I was told the motor has to be dropped. Can the body be lifted with a regular engine hoist?. I really would hate to junk this car being I dumped over $7k into it the last 6 months since I got it (including price of car), plus the wife really likes it. Thanks for any help with these questions. My gut says its the head gasket but I was hoping for a better case scenerio.

johnplara
11-15-06, 06:07 PM
Hold your horses there on the ye old head gasket front. Correct if I am wrong, but I doubt I am, Like in 4.9, the water pump is belt driven, meaning connected to the camshaft pully. Ergo, the faster the motor reves, the faster the water pump spins, the faster the water pump spins, the more pressure and velocity it sends the coolant sloshing through the system, or am I crazy. The only definitive and sure ways to check for a head gasket leak is to do a compression test, a bitch on these cars, or a leak down test. First deal with the imediate leak, and then after that is taken care of, see what happens and if it is still blowing coolent or getting toasty, check for head gasket.

codewize
11-15-06, 06:35 PM
Ok two things here. Definitely make sure it's the head gasket before you start tearing at things. Get a leak down test done and prove it. There's no certainty to any of our responses.

Secondly the water pump is belt driven as it is on all cars but let me ask you. Have you ever reved a car with the radiator cap off? The coolant level drops, it doesn't rise and if it's coming out of there pressurized that's not whats happening. I don't think the overflow would even release at 238 deg. I think that system is having foreign pressure introduced from somewhere.

To answer your question I thing I understand a HG job to run about $3000 give or take of course.

zonie77
11-15-06, 07:04 PM
It sounds like a head gasket but as someone said "You wouldn't have heart surgery unless you were sure it wasn't heartburn" or something like that!

Do a cylinder pressure test (not a compression test) on it to be sure. If it's head gaskets you can fix them yourself. I recommend that over buying a used engine if yours is otherwise good. See the N* head gasket repair thread in tech tips, your questions will be answered.

Dadillac
11-15-06, 07:24 PM
If the thermostat failed it will heat up and build pressure rapidly. Add revving to the equation and you can have the result he is seeing. I will not say that the head gaskets can't be at fault. But damn, why is it when somebody posts any coolant issue, everybody wants to scare the hell out of the poster, by faulting head gaskets right away. I will state here that I do not believe that the hg's are gone. If I end up being wrong so be it. But it definitely sounds like a thermostat or the radiator cap. I would not start by doing a compression or leakdown test. Start by buying a new thermostat (they can be bad right out of the box) and testing it in a pot of water on the stove. After you see that it opens, install it in the engine, along with a new radiator cap. Both of these are quite inexpensive, and very well may be the fault. If this doesn't correct the issue I would suspect the water pump or belt. Then and only then would I suspect a hg.

Don

mgb4tim
11-15-06, 07:49 PM
sounds like my 99's head gasket woes. I tried to pretend it was OK, but ended up limping to the dealer, 2 weeks later I gave them the loaner back and a $250 deductible. Told me the job is normally $2500-3000. Raise the car up and drop the whole package from underneath.

bummer:mad:

Destroyer
11-15-06, 07:49 PM
Whew!. Thanks for all the help guys!. I'll give the thermostat and radiator cap a shot when I get the time. Far as the water pump being bad well.......its only 3 months old and the belt was done at the same time. I can start the car up and drive now and the motor sounds great, not a tick but then it heats up and starts spewing up anti freeze all over the place. Times like these I really appreciate my '91 Fleetwood RWD. Even my '97 Mercedes S320 looks simple by comparison. I'll keep you guys updated and if it is the head gaskets; let me know what parts you need from the car.

Quick question to Ranger: You say the t stat is located from where the bottom radiator hose goes to the motor?. Is this easy or a PITA to do cause I cant even see the bottom hose from the top?.

Ranger
11-15-06, 07:58 PM
While head gaskets where my gut feeling, I will say again, do not condemn them on gut feelings without proof (cylinder pressure test), be it before or after you check the cap & thermostat.

Dadillac
11-15-06, 07:58 PM
Look at this pic. Look under the visible hose and you will see the waterpump / thermostat housing.

Don

Ranger
11-15-06, 08:00 PM
Quick question to Ranger: You say the t stat is located from where the bottom radiator hose goes to the motor?. Is this easy or a PITA to do cause I cant even see the bottom hose from the top?.
Once you get the air filter box and intake ducting out of the way it will be easier to see and get at.

PaulB
11-17-06, 05:53 PM
I have a 98 Deville Concours that spits out coolant every now and again, maybe a pint or so through the overflow. I changed the thermostat, r-cap, no leaks in the hoses; bought a combustion leak detector kit from NAPA; it showed that the cooling system has exhasut gas in it and the sytem has presure in it even after sitting all night. I tucked an empty antifreeze bottle in behind the headlights and ran a longer hose from the overflow to catch the coolant as it comes out. From what I've read online the exhaust gas will cause a chemical reaction with the antifreeze and cause corrosion in the system ,so I thought I could just dump the old out of the bottle and add new. Anyway I have not brought it in to the local dealer but was wondering if anyone has any idea how long before the corrosion becomes an issue? Car has 60K on it and I've got 7K invested having only had the car for 6 months. Sorry for tagging this to this posting but I'm new at this so didn't know where to start.

Ranger
11-17-06, 08:36 PM
I do not know if exhaust gasses have any chemical reaction with coolant, but I am pretty sure the head gaskets will get worse and the car will be undrivable long before any chemical reaction can do any greater harm than the head gasket.

C170B
11-17-06, 11:56 PM
Check the thermostat housing to see if it is the latest version.

Write VIN number down and phone the parts dept of sev cadillac delerships.

Early model N* were factory equipped w a black thermoplastic housing that dev slight warpage allowing air into system, then thermostat slowly gets COOKED stops working. GM wants all black thermostat housings replaced quietly, they don't want to talk much about it.

Another sometimes sleeper problem that fails to get diagnosed is lower radiator hose collapsing due to a minor pinhole that lets air into system whenm thermostat opens. Hose may also collapse due to failed rusted spring inside the lower hose. Why would factory put a steel spring inside a high tech aluminum alloy engine? Hose factory sales techs don't want to talk about role of spring in hose. Some one may ask them to bear replacement cost of engine repairs.

The above may never apply to your car and I hope you find a simple solution on the forum and get ahead of the over heating problems. Most N* are driven a 100K miles without problems.

regards

JimHare
11-18-06, 06:49 AM
My wifes '98 Deville <snip>
... its coming from the overflow hose connected to the radiator right by the cap.

Hold on a minute here - if your description is accurate, this sounds like it may be the connection for the hose at the expansion tank, not the 'radiator' itself.

Is the fluid coming OUT of the bottom of the overflow hose, or leaking around the 'nipple' where it connects to the plastic expansion tank? I had a similar problem on my '99 Deville, the nipple itself cracked at the tank and caused coolant loss that would not have otherwise occurred. Ended up replacing the expansion tank.

Check this out before you start tearing out the water pump or worry about head gaskets....

Destroyer
11-19-06, 09:33 AM
UPDATE: Replaced the thermostat and the problem IS fixed. Before the temperature would keep going up till I shut the car off at 238 degrees. Now she maxes out around 228 degrees and then cools back down to 196 or so. This is the way the car ran before the car started overheating. I almost bought a new Expedition the other day cause I was convinced it was the head gasket. So all is well and I am relieved that a new car purchase is not necessary at this time. Thanks to all for the help.

Dadillac
11-19-06, 10:14 AM
Destroyer

Glad you had an easy and cheap fix.

Don

I~LUV~Caddys8792
11-19-06, 11:43 AM
So what should a Northstar run at? 210*? 220*?

Destroyer
11-19-06, 11:48 AM
So what should a Northstar run at? 210*? 220*?

I have not driven this car much but it seems to go up to the 220's and then comes back down to the 190's. Doesn't like sitting at traffic lights.

I~LUV~Caddys8792
11-19-06, 11:58 AM
From what I remember, that seems pretty normal. That '93 STS I drove topped out at 208*-210* after 20 minutes.

Ranger
11-19-06, 04:10 PM
So what should a Northstar run at? 210*? 220*?
My '97 Deville ran a consistant 206 (summer) and 213 (winter).

codewize
11-20-06, 01:44 PM
Wow glad to hear it was a easy fix. I'm surprised that caused what you were seeing. The N* is truly unique

Destroyer
11-21-06, 10:06 PM
Wow glad to hear it was a easy fix. I'm surprised that caused what you were seeing. The N* is truly unique
Thanks man. That was a bit of a scare. Since the last post I have noticed the car still has a few drips of anti freeze after use. It did this before the overheating problem and its doing it again. It still smells of coolant when the car is parked in the garage. It has done this since I bought it. I added some Prestone stop leak (for radiators) before I had this problem to stop those drips of anti freeze. Seems as if that stop leak caused the t stat to gum up. That stuff was all over the radiator cap and t stat. I'll never try that again. Car runs strong and not too hot just like it used to so we'll drive this car to the ground.

Ranger
11-21-06, 10:19 PM
I'd flush that crap out of it (if you can) and use the GM (Barsleaks) sealant tabs. That is what they are designed for, without gumming up stats & caps.

Destroyer
11-28-06, 09:54 PM
I'd flush that crap out of it (if you can) and use the GM (Barsleaks) sealant tabs. That is what they are designed for, without gumming up stats & caps.Done!. Thanks for the help and advice.:thumbsup:

C170B
12-01-06, 08:15 PM
When your remove the current thermostat test it on kitchen stove w thermometer. Buy the best GM T stat and as prior post stated test it before installation.

There is not enough QUALITY built into any automotive T stat today. AS you probalbly already know it is a WAX PELLET "motor" that opens and closes T stat. A major problem w T stat is the paper thin metal covering the wax pellet. Microscopic cracks allow wax to escape and T stat slowly loses function. Some engineers think it is air in the cooling system that sets up the T stat for failure.

I hope you escape the HG issue. Tell all to not wait until T stat goes bad.
Replace 2-3 years or some mileage interval.

Info on this forum helped save my N* . Same issue as your problem

My N* drives great smooth and powerful 171K.

regards

codewize
12-03-06, 10:49 AM
Whew. It's nice to see a hi mileage N* for once.

riverman62
12-03-06, 07:39 PM
Im afraid its your head gasket probley #2 plug check your spark plugs to see what one is discolored