: Engine Running Hot..239 at shut off



blunted
01-03-05, 02:03 PM
Within the past 2 weeks i've seem my 94 Eldorado reach 230-232 degrees coolant temperature which is new because I purchased the car in May and it never went that high even in the summer. Today it was occuring again and I waited untill it hit 228 and parked it. A couple minutes later I turn the key to check the coolant temperature without turning the car on and its at 239!! :crying: My jaw dropped and I have no idea what could be causing this. I also noticed oil dripping a little more than usual. Any help with this matter is GREATLY appreciated!

Spyder
01-03-05, 02:13 PM
Its common for the temp to rise a bit after the engine is shut down...and 228 isn't really all that hot. Mine will hit 228 if I sit for too long, then the fans kick in and cool her back down to 210 or so before they shut off. The fans won't come on at all until low to mid 220's, so I wouldn't worry about the temp all that much. Just make sure that the fans are running...next time its up to 226 or so, jump out and look under the hood to be sure they're going.

blunted
01-03-05, 02:18 PM
The fans are running perfect , and I never really thought 228 was a problem but after 6 months for 232 to come up and then 239 at shut off seems like somethings going on to make this suddenly start occuring. Isn't 240 like the boiling point? And thanks for the reply spyder!

Spyder
01-03-05, 02:36 PM
the N* is supposed to be able to go 265 before boiling over, IF everything is working properly, such as surge cap, thermostat, water pump, proper mix of antifreeze and water, etc...I dunno, hopefully someone on here will be able to help you out!

blunted
01-03-05, 03:26 PM
Ok so I just read a post by Bbob saying that even 239 is far from overheating. So i guess I have nothing to worry about.. still find it weird that this just magically started happening. :hmm:

cart69
01-03-05, 05:07 PM
my 94 n* has always hit 232 when sitting or so and never higher, the fans come on then it goes down, but no problems other than a couple seeping hose connections i noticed the other day!! sounds ok to me

My firebird before i changed the thermostat to a cooler one ran 220 all the time, i have seen many newer cars that run a temp around there and thats normal, i wouldnt worry should be just fine

STS 310
01-03-05, 06:12 PM
I think your OK, but a coolant change may not hurt either. Make sure you t-stat is working correctly also.

CAJUN-Z
01-03-05, 08:16 PM
Radiator could need replacing. Had a Z-28 that constantly showed high temps. locked in fans and had radiator flushed professionally. Nothing helped. Lowered thermostat opening point (hypertech 165*) to no avail. Replaced radiator and PRESTO...overheating fixed!...

BeelzeBob
01-03-05, 08:43 PM
Within the past 2 weeks i've seem my 94 Eldorado reach 230-232 degrees coolant temperature which is new because I purchased the car in May and it never went that high even in the summer. Today it was occuring again and I waited untill it hit 228 and parked it. A couple minutes later I turn the key to check the coolant temperature without turning the car on and its at 239!! :crying: My jaw dropped and I have no idea what could be causing this. I also noticed oil dripping a little more than usual. Any help with this matter is GREATLY appreciated!


Keep an eye on it but it is likely perfectly normal.

In the summer, when the AC is on, the fans are running all the time so the coolant temp usually stays relatively low since there is air flow all the time and the fans are never really activated by the coolant temp...since they are running anyway for the AC. Most of the time in the summer the fans are not really required as the air flow is actually more than the coolant temp needs to stay cool. But, the fans are needed for the AC condensor so they keep the coolant low as a side benefit.

In the winter, the AC is disabled (the compressor does not run below 40 degrees F ambient temp) and there is no heat load on the condensor. The fans do not run since the AC is disabled unless the coolant temp gets above 225. So...as odd as it seems...it is quite common to see the coolant actually get to a higher temp in the winter when idling than in the summer, especially in milder summer weather when the AC is on.

228 at idle is not hot at all....and to see 239 a few minutes after shutdown like that is perfectly normal. The underhood and coolant temps in the heads will continue to rise for as long as 20 minutes due to latent heat in the metal of the heads and no circulation of the coolant.

A Northstar cooling system with a properly operating 15 PSI pressure cap (OEM cap) and a fresh 50/50 coolant/water mix in the system will not boil until 265 degrees F. I wouldn't worry about the sytem unless it starts getting to 245-250 regularily...especially if the load is light. Climbing hills in the summer it is common for the coolant to reach 250 or so...with no problems at all. The system is still in control until it boils at 265 and will not hurt the engine even then. You will get all sorts of warnings before the engine really overheats and then it will automatically enter the limp home protection mode if the temps go too high.

brmurph
01-03-05, 09:12 PM
Keep an eye on it but it is likely perfectly normal.

In the summer, when the AC is on, the fans are running all the time so the coolant temp usually stays relatively low since there is air flow all the time and the fans are never really activated by the coolant temp...since they are running anyway for the AC. Most of the time in the summer the fans are not really required as the air flow is actually more than the coolant temp needs to stay cool. But, the fans are needed for the AC condensor so they keep the coolant low as a side benefit.

In the winter, the AC is disabled (the compressor does not run below 40 degrees F ambient temp) and there is no heat load on the condensor. The fans do not run since the AC is disabled unless the coolant temp gets above 225. So...as odd as it seems...it is quite common to see the coolant actually get to a higher temp in the winter when idling than in the summer, especially in milder summer weather when the AC is on.

228 at idle is not hot at all....and to see 239 a few minutes after shutdown like that is perfectly normal. The underhood and coolant temps in the heads will continue to rise for as long as 20 minutes due to latent heat in the metal of the heads and no circulation of the coolant.

A Northstar cooling system with a properly operating 15 PSI pressure cap (OEM cap) and a fresh 50/50 coolant/water mix in the system will not boil until 265 degrees F. I wouldn't worry about the sytem unless it starts getting to 245-250 regularily...especially if the load is light. Climbing hills in the summer it is common for the coolant to reach 250 or so...with no problems at all. The system is still in control until it boils at 265 and will not hurt the engine even then. You will get all sorts of warnings before the engine really overheats and then it will automatically enter the limp home protection mode if the temps go too high.

Bbobynski can you comment on the Northstar limp home mode with vehicles with over 100,000 miles? I know that you have said in the past that this works very well and has been tested extensively by GM, I assume the tests where on relatively new motors though, what about older ones? Everyone I have talked to says don't let the Northstar over heat or the head gasket will be the next thing that will need to be replaced because of pulled head bolts. I think even you have even mentioned that the older the motor the more of a chance that head bolts/head gaskets will be a problem. Bottom line if my older Northstar overheats on the freeway and I can easily have it towed should I shut it down and have it towed or use the limp home mode (assuming less then 50 miles). As always thanks for you expert advise.

blunted
01-04-05, 01:19 AM
Thanks Bbob for breaking it down.. at least I know not to crap myself if I ever encounter 240. STS.. thermostat was replaced as well as the water pump, tensioner, and belt about 4 months ago and it was running pretty cool until now.. everything but the pump was preventive maintenance. And about the oil thing, the brilliant guys at the cadillac dealership near me seem to have overfilled my oil when I got a change. I checked it and it was up at the full mark and creepin past it, now I'm wondering if the drip of oil i'm getting which is more than just a couple drops is the excess burning off.

CadiJeff
01-04-05, 01:43 AM
try changing your air filter when I change mine there is usually a 8-15 degree drop on avg.

inmycadillac
01-04-05, 06:23 AM
my 96 deville runs around 203 pretty regularly....and its 30 below up here!!! i do use a quart of oil every 700 miles, but with a huge engine and those temps, thats prolly good??!!

ShadowLvr400
01-04-05, 09:23 AM
Actually, going through a quart every 700 miles is pretty quick. The 4.6 isn't really huge, and while the northstar is known to eat oil, a quart every 3000 miles is a bit more normal. Every 700 indicates a larger leak somewhere... At least to me.

BeelzeBob
01-04-05, 02:00 PM
Actually, going through a quart every 700 miles is pretty quick. The 4.6 isn't really huge, and while the northstar is known to eat oil, a quart every 3000 miles is a bit more normal. Every 700 indicates a larger leak somewhere... At least to me.


Ahhh.....no. A quart every 700 miles is on the high side but still not something that indicates a problem or a cause for concern. I would suspect a very aggresive crosshatch on that engine block probably and a set of rings that might be a little sticky in the ring grooves from some carbon buildup but nothing indicating an engine "problem" or imminent failure at all.

BeelzeBob
01-04-05, 02:02 PM
Thanks Bbob for breaking it down.. at least I know not to crap myself if I ever encounter 240. STS.. thermostat was replaced as well as the water pump, tensioner, and belt about 4 months ago and it was running pretty cool until now.. everything but the pump was preventive maintenance. And about the oil thing, the brilliant guys at the cadillac dealership near me seem to have overfilled my oil when I got a change. I checked it and it was up at the full mark and creepin past it, now I'm wondering if the drip of oil i'm getting which is more than just a couple drops is the excess burning off.


Depends on where it is dripping from....

Overfilling is definitely NOT the way to go with the Northstar for everyday driving. Check the oil level HOT and keep it at or below the full mark. If it is over it will not ruin anything but it will certainly contribute to some excess comsumption until it gets below the full mark. I would keep it halfway between full and add or on the add mark if you want to top off.

BeelzeBob
01-04-05, 02:03 PM
try changing your air filter when I change mine there is usually a 8-15 degree drop on avg.


Changing your air filter element drops your coolant temp..????....no way.

BeelzeBob
01-04-05, 02:15 PM
Bbobynski can you comment on the Northstar limp home mode with vehicles with over 100,000 miles? I know that you have said in the past that this works very well and has been tested extensively by GM, I assume the tests where on relatively new motors though, what about older ones? Everyone I have talked to says don't let the Northstar over heat or the head gasket will be the next thing that will need to be replaced because of pulled head bolts. I think even you have even mentioned that the older the motor the more of a chance that head bolts/head gaskets will be a problem. Bottom line if my older Northstar overheats on the freeway and I can easily have it towed should I shut it down and have it towed or use the limp home mode (assuming less then 50 miles). As always thanks for you expert advise.


Well....hard to say. I have never run 100K engines without coolant into the limp home mode so I can only guess.....

Certainly the older the engine the more succeptable to thermal damage it is. The head bolt interface in the block has been thermally stressed thousands of times, the head gaskets have been thermally stressed thousands of times, etc.... so, I think it is safe to say that the engine will be less robust in the event of a severe overheat condition that led to the limp home mode operation. I have seen engines subjected to the limp home operation due to loss of coolant that were subsequently run for over 100K with no problems but they were relatively low mile engines when the limp home occurred (although one I remember was near 50K when it occurred and it subsequently ran to 120K) Also, keep in mind that with all the limp home testing it is impossible to factor father time into the equation. Any corrosion of the engine or the gasket substraight over time..or any galvanic action between the head bolts and the threaded holes, etc... is hard to predict.

I would avoid limp home operation if at all possible. Limp home was designed developed and tested as a safety feature to avoid being stranded on the freeway at 1:00 AM in a bad part of town because the engine just seized due to a blown radiator hose. It was not put in the car as a "convenience" item so that you could continue to drive with no coolant until it was convenient to get the problem fixed. If there is an overheat problem the answer is to always stop the car and determine the problem and fix it or have it towed or whatever....unless you are in physical danger and have to drive...with the limp home it gives you the ability to make it to a safe place...i.e..you don't need to stand by the side of the expressway with traffic 1 foot away...drive it to the nearest off ramp and get off the road to a safe place. Then stop as soon as possible, determine what the issue is and have it towed if necessary.

The limp home mode is an excellent feature and a real safety device but it is not infallible and the older the engine gets the more succeptable to damage it is in a thermal event like an overheat. I would never intentionally drive MY Northstar engine in the limp home mode unless it was ABSOLUTELY necessary. And then, only the shortest possible distance. That is just common sense to me.

blunted
01-04-05, 10:18 PM
Ok so just when I thought I could RELAX for a change with this car :disappoin .. since my temps were o.k. I notice just how much oil I'm leaking when I moved my car to the correct side of the street to park after it was sitting for the whole day. And of course to my luck I see i'm leaking from 2 places and one of those isnt small at all. My car NEVER did this and I cant think of how its happening.. too much oil by the dealer at this last change is the only thing "different" this cars been thru within the past week besides getting new rear struts. Is there any place where I could see a picture of the underbody of a 94 eldorado or a diagram so I could refer to where I see it leaking from.. please excuse my lack of knowledge in the matter. Thanks!

CadiJeff
01-05-05, 12:19 AM
bbob I swear on my car that for some strange reason it does I can't explain it but under the same driving conditions a new filter (and yes it is the only change) makes the temp lower.

mechanix
01-15-05, 03:38 PM
To Blunted: Your sudden oil leak combined with a hotter running engine is a big red flag! I'll bet you've pulled some head bolt threads. My '97 DeVille/Northstar overheated and leaked oil, and it was all due to head gaskets! I was loosing coolant AND oil externally from the rear (right) head due to the head bolt threads breaking out in the engine block, ergo loosening the head bolts, ergo allowing the head gaskets to leak. I might add that a compression test prior to teardown revealed nothing. I got 185 lbs. on all cylinders except #1, which was 165 lbs., but my coolant/oil leaks were in the vicinity of cyls. #6,8. Of course I eliminated all other possible causes of overheating first: having the radiator rodded out and flow tested; replacing the water pump; putting on a new 15 lb. recovery tank cap; fresh 50/50 mix of DexCool; checking electric fan operation and a new 190 degree thermostat (which I boil tested on the stovetop with a thermometer for opening and closing temps).

Also, overheating the engine several times in the process of trying to find the problem resulted in burning all the exhaust valves in one head. So a complete, 32-valve grind had to be performed as well. Additionally, both heads were warped .003"-.004" and had to be milled, since the service limit is .002", according to GM.

If I were you, I think I would try sending the radiator out for servicing just to rule it out. If you have done that and checked everything else that I previously mentioned, jerk that engine out and fix it! Don't wait until you sustain the type of damage that I did. :banghead: You'll soon be hitting operating temps of 170 degrees before you can get it pulled off the road and shut down. Good luck!