: Northstar overheating



baggedimpala
05-27-04, 06:48 PM
:rant2:

ok, been having trouble with the cooling system of my 94 deville concours since I bought the dang thing.

today, on the way home from work, (12 miles), after some slightly spirited driving, it overheated on me. I know the coolant level was fine bacause yesterday I put a new radiator capo on, and topped it off at that time.

the "engine coolant hot" light came on as I was exiting the expressway, and when I pulled in my driveway and got out ( about 1200 feet), I seen a nice trail of water behind me.

I know I was running a good mix of antifreeze/ water. The water pump and thermostat are new. So is the water pump drive belt. The radiator seemed fine when I flushed the system 2 weeks ago, I stuck my garden hose in the top next and turned it on, water was flowing freely from the lower hose.

I'm at my wits end on this car, and am contemplating burning it to the ground to celibrate Memorial day.

Any ideas folks?

zonie77
05-27-04, 07:33 PM
You are going to have to do a compression test and/or a cylinder pressure test.

You have the symptoms of a bad head gasket but until you test for it you can't be sure.

RLLOVETT
05-28-04, 01:15 AM
Wait a minute! If the water pump's working and the rad cap's working, what else would make it overheat besides the head gaskets?!

eldorado1
05-28-04, 01:39 AM
Wait a minute! If the water pump's working and the rad cap's working, what else would make it overheat besides the head gaskets?!
Leaking hoses, pinhole leaks in the radiator, inoperative fans to name a few

baggedimpala
05-28-04, 02:30 PM
the cooling system was recently pressure checkd for 3 days straight..
it will sit and idle all day and not overheat
fans come on when theyre supposed to
i can drive on the streets and its fine

its just when i drive fast on the highway, and put it through its paces, that it acts up..

eldorado1
05-28-04, 03:55 PM
the "engine coolant hot" light came on as I was exiting the expressway, and when I pulled in my driveway and got out ( about 1200 feet), I seen a nice trail of water behind me.

Was it just plain water, or did it look like antifreeze? Was it coming from the tailpipe? Does you exhaust smell sweet (like coolant)? If it looked like regular antifreeze, wasn't coming from the tailpipe, and exhaust smelled normal, I would say you have a leak somewhere that only shows up at certain times (perhaps when it gets warm a crack in your radiator opens up... donno) If all that wasn't true, I'd still run a compression check to make sure.

BeelzeBob
05-28-04, 03:59 PM
Did you check the tensioner on the water pump drive belt carefully..??? It might be sticky or frozen and not tensioning the water pump drive belt. Exercise it and lube the pivot point to be sure it is working correctly.


Take the 3/8 hose off at the pressurized surge tank with the engine cold. Start the engine momentarily. There should be a steady, strong flow of coolant from the 3/8 hose with the engine running. If not, trace the hose back to the engine where it connects immediately beside the upper radiator hose. Take the 3/8 hose off the nipple beside the upper radiator hose on the engine and start the engine. Coolant should flow from the nipple on the engine ...it is actually a hollow bolt and coolant should come from the orifice inside the bolt when the engine is running. If not, then remove the bolt and find the obstruction. That 3/8 hose is the vapor vent for the water pump and it must be flowing coolant or the water pump will injest vapor and stop pumping....commonly at full throttle/high RPM/high load when it needs to flow the most...resulting in overheating.

The 93/94/95 Northstars often have head gasket problems about now due to lack of cooling system maintenance. If the green, conventional coolant in those engines was not changed frequently (24-32K/2-3 years) the corrosion inhibitors would fail and the engine would be damaged by internal corrosion including head gasket failure.

You can remove the spark plugs and pressurize each cylinder with 120 PSI shop air to check the head gaskets. Pressurize the cylinder and watch the cooling system at the surge tank for bubbling indicating a leak.


If the coolant supplement recommended is installed into the surge tank instead of the radiator hose it can plug the hose from the surge tank to the water pump causing overheating symptoms, also. You might check that the large hose from the surge tank to the water pump inlet is clear and unobstructed.

baggedimpala
05-28-04, 11:06 PM
the coolant was most certainly coming out of the overflow hose.

bbob, I read through this list and while changing out the water pump, etc, I made sure to do everything just as you prescribed.

I may try the air in the cylinder trick tomorrow. Do I need special fitting for this?
Also, any tricks involved in accessing the rear plugs? they seem buried beneath the coil pack.

zonie77
05-29-04, 12:49 AM
The coil pack comes off pretty easily.

Several people have had exactly the same symptom as you...runs fine under light load, idling, level cruise etc. Under a heavier load, mountains, fast driving etc they overheat dramatically.

Ask Shadowlvr400. I think his acted that way. My brother's acted that way too.

baggedimpala
05-29-04, 11:53 AM
what did they do to fix it?

zonie77
05-29-04, 03:52 PM
Replaced the head gaskets.

BeelzeBob
05-30-04, 02:25 AM
the coolant was most certainly coming out of the overflow hose.

bbob, I read through this list and while changing out the water pump, etc, I made sure to do everything just as you prescribed.

I may try the air in the cylinder trick tomorrow. Do I need special fitting for this?
Also, any tricks involved in accessing the rear plugs? they seem buried beneath the coil pack.

I was NOT talking about the coolant overflow hose.....

The 3/8 hose that I am talking about is an integral part of the coolant system to the surge tank...not the overflow hose from the cap.

You must check the vapor vent line for flow. I doubt that you did that when changing the water pump.

The 3/8 hose that I described attaches to the side of the pressurized surge tank...not at the cap fitting.

bobvondutch
06-01-04, 06:26 PM
Bagged:
Have had the same problem on a 97 Eldo ETC for the last couple of weeks: problem (overheating and discharge) only happens after some "acceleration runs". Had it at the dealer last Friday, and it took him three hours to find the problem. I'll post a new thread about the testing, but he finally agreed it was head gaskets. Check the new post when you have time, and good luck.

RLLOVETT
06-01-04, 08:28 PM
How many miles? Also, mine ('94/275hp/130k) NEVER leaks it onto the ground yet it will drink/burn a varying (by a lot!) amount. E.g., yesterday I topped off the coolant in the driveway (but engine off); today I drove the car for the first time since the topoff and the CHECK COOLANT LEVEL message came on at about mile 25...I haven't had a chance to check the reservoir but I can tell from the way the temp shoots up that it's at leasta half gallon low...at least the sensor works...

rickbraley
06-08-04, 05:22 PM
Did you ever resolve your problem??

I have a 94 Eldorado with 93K on it that has the exact same problem.

It consumes enough coolant in about 25 - 30 miles to cause the engine to overheat. Once it overheats it blows remaining coolant out the overflow.

I have done everything I can think of to fix this thing and it is still doing the same thing.

Replaced both head gaskets, new water pump, belt, thermostat, pressure tested radiator, heater core, etc. No water in oil, no signs of water being burned in the combustion chambers, etc.

I am at a loss. Desperate for advice.

Thanks

rickbraley@yahoo.com

RLLOVETT
06-08-04, 10:24 PM
Rickbraley, THAT's ugly!! Replacing the head gaskets and it STILL drinks coolant!

Mine seems to be worse by the day (course it's hot here now--90s for a couple of days)...seems to be fluctuating more, temp wise. I'll cruise at 60 and it'll run about 212 and then when I'm toodling around town at 35-40 it'll jump up to the 250s...today I let it coast down a good hill in neutral as I was almost home and the limp-home mode, with which I am all too familiar, makes me nervous...

BeelzeBob
06-08-04, 11:45 PM
Did you check the water pump drive belt tensioner carefully..??? It needs to be exercised and the pivot point lubed to make sure it is tensioning the belt correctly.

Also, check the vapor vent line as mentioned above. Take the 3/8 hose off at the pressurized surge tank when the system is cold. Start the engine briefly. Coolant should piss from the 3/8 hose when the engine is running. If not, the water pump cannot vent itself of vapor and it will lock up and not pump and the engine will over heat.

If you have modified/bypassed/eliminated/plugged the throttle body heater circuit this is likely the problem as that circuit is also the vapor vent line mentioned and it MUST be flowing coolant correctly.

Are you positive that the coolant is a 50/50 mix?? An incorrect mix of coolant concentration will cause premature boiling and the symptoms you mention also.

Even though the head gaskets were replaced...if the above check out fine then I would recommend you take the time to pull the plugs and pressurize the combustion chambers with 120 PSI shop air one at a time to make sure that there is no leak to the cooling system from the combustion chamber. If a cylinder bore liner is cracked or something like that it could cause the same problem and would not be corrected with a new head gasket.




Did you ever resolve your problem??

I have a 94 Eldorado with 93K on it that has the exact same problem.

It consumes enough coolant in about 25 - 30 miles to cause the engine to overheat. Once it overheats it blows remaining coolant out the overflow.

I have done everything I can think of to fix this thing and it is still doing the same thing.

Replaced both head gaskets, new water pump, belt, thermostat, pressure tested radiator, heater core, etc. No water in oil, no signs of water being burned in the combustion chambers, etc.

I am at a loss. Desperate for advice.

Thanks

rickbraley@yahoo.com

rickbraley
06-09-04, 01:24 PM
Thanks guys for your responses.

I will recheck all the items mentioned...

I sure don't want to drop the drivetrain again! Man was that a lot of work!

I really want to get this thing functioning properly. I really like the car...

propertypro
06-09-04, 06:34 PM
the cooling system was recently pressure checkd for 3 days straight..
it will sit and idle all day and not overheat
fans come on when theyre supposed to
i can drive on the streets and its fine

its just when i drive fast on the highway, and put it through its paces, that it acts up.. I have found (after much testing) that a head bolt pulled when my SLS overheated and the cylinder pressure would blow out the coolant(and still pass a cooling sys. pressure test). It ran fine without overheating on surface streets, but on the E-way about two minutes before coolant was gone. The next step is a low milage used engine. Sux but I love the oil using screamer!