Overheat

[pojawis]

Working on my 2001 SSei, 242K miles. I had a coolant leak and couldn't find it until I had a high heat/overheat condition. The temperature gauge was in the red, so I shut it down. The culprit was a cracked heater elbow fitting (Help! part # 47065). I replaced both elbows and the termostat (it needed it) and refilled the radiator. The engine seemed to run fine for a day or so. It now runs from 200-240 degrees, going up and down with little rhyme or reason. On shut down, air bubbles into the coolant reservoir and I can hear air bubbling through the radiator hose. Today, the temp was approaching the red, so I turned on the heater and this reduced the engine temp to 200 degrees. It then went back up to about 240. There are no other apparent external leaks. The water pump seems to be working as coolant looks to be moving through radiator.

I've read through past posts, searching for overheat related topics. Will be looking at the LIM and UIM gaskets as a cause, although the engine runs smoothly. Will perform the coolant bleed procedure (drill thermostat, etc.).

The question: What else might cause this condition?

Thanks for any help.

[myfirstbonnie]

Did you drill the thermostat? It may have air trapped in the engine.

http://www.pontiacbonnevilleclub.com/fo ... f=53&t=159

You also may have a failed water pump. Do you know how old it is?

Are the fans coming on? They should come on when the air conditioning is turned on.

Other than that, do a compression check to see if the overheat condition caused a head gasket to fail.

[willwren]

The brand of thermostat can mean as much as trapped air (temps going up and down point to air in the system).

Are you still running DEXcool? www.dex-cool.net READ this link!

Those high temps may have over-stressed what was left of your LIM gaskets. Have they ever been changed?





Bottom line is that you may have a can of worms now, but if you have a good wrench in your hand, you can fix it all for under $250.

[pojawis]

Thanks myfirstbonnie and willwren for the quick replies.

Answers to your questions (in no particular order):

Got the car with 89K miles on it. The FIRST thing I did was flush the DexCool and replace with green. Had a reputable shop do that for me.

I believe it's a Stant (sp?) thermostat. Have not drilled it yet.

Doubtful that the gaskets were ever changed, although I'm told the previous owner was very meticulous about the car.

I've put about 150K miles on the car and haven't changed the water pump, so I'm sure it's due.

I did check the fans and they come on as they should; with a/c and when the car was shut down and hot.

Allow me to ask a stupid question: Compression check = cylinder compression, yes? Any unique procedure for this engine or is it like most? The bulk of my wrench turning & tinkering is on OBD I and previous stuff (mostly previous), some military vehicles, and aircraft.

Thanks again.

[myfirstbonnie]

Compression check is the same, nothing different there.

There are issues with the LIM (lower intake manifold) gaskets leaking coolant. If you look at the point where the head, block and LIM meet, do you see black (plastic) or aluminum gaskets.

Try getting all the air out, but you will eventually want to replace those gaskets if they have not been done yet. Signs of failure are loss of coolant, milky looking oil, milky looking film inside oil fill cap, white smoke from tail pipe and others.

[pojawis]

I'll have a closer look soon and will post my findings. Frequent oil changes have not shown any signs of coolant contamination. She's about due for another, so I'll check closely. No white smoke.

Thanks again.

[myfirstbonnie]

You will know if you have coolant in your oul. It will look like the insides of a 3 musketeers candy bar. It will be a milky brown color.

[Mac077]

Just a thought as this kind of happened to me when I replace my water pump...try bleeding the air from the thermostat while the car is running until you get a solid stream! The symptoms sound the same!!

[pojawis]

Will do and thanks again. Been busy with family stuff and haven't gotten to the Bonneville. When I do, I'll let y'all know my findings..

At the risk of sounding gushy, I'm very appreciative of the help I've gotten from this forum. Hope I can repay favors.

[pojawis]

Thermostat drilled, reinstalled and bleed procedure completed. Temp seems normal. One symptom remains, however. Bubbles are seen in the reservoir while engine is running and for a short time thereafter. There seem to be no leaks at water pump nor heater elbows. Will run bleed at thermostat housing again tomorrow.

Checked for black plastic LIM gaskets and found same. I reckon replacing with aluminum gaskets is now on the list. . .

[00Beast]

Honestly, bubbling in the coolant is generally bad head gaskets. Being you overheated it, there are odds that they might be bad. If you tear it down and the LIM's aren't that bad, I think you should probably yank the heads and have them looked at by a machine shop and new gaskets all the way up.

[Bing]

If the bubbling doesn't seem to let up, then sorry to say its top end rebuild time.

[02ssei]

If the bubbling doesn't seem to let up, then sorry to say its top end rebuild time.

X2

wanted that to have 00beasts post in there too. oh well. i'd also be looking at the head gaskets.

one thing though, i thought a pressure check would show if the head gaskets were bad. i know i've found bad gaskets by doing pressure tests before.

[Bing]

Yes, that is true. You could verify our thoughts by doing that and then you'll know for sure.

[00Beast]

A pressure test will confirm a leak, it can't determine where though.

[Archon]

Something that will help to pinpoint a problem is a cylinder leak-down tester. Kind of a compression tester in reverse. Find a cylinder with 30% or more loss, then check for where the air is escaping. In your case, the head gasket leak would show up as bubbles in the radiator and/or overflow tank. These are a couple of articles explaining the tests.

http://www.carcraft.com/techarticles/11 ... ewall.html

http://www.mobiloil.com/USA-English/Mot ... _Test.aspx

[pojawis]

The cylinder leak down test is one with which I'm familiar as this is how we test compressions in air cooled aircraft engines. I wondered if there was an application for automobiles as it seemed easier, or least more accurate, than the usual procedures.

The articles referenced are helpful, but I still wonder: 1) how to keep the engine from turning when applying the air pressure. 2) how to determine if it's a leak past the rings or through the head gasket - will bubbles show up in every cylinder? Or even if it occurs in just one cylinder, is head gasket bad?

I'll do some more research and see what I find. I'll post progress.

Thanks again.

[00Beast]

The engine won't turn over when you apply air pressure. The friction of the rings and the accessories, etc is enough.

Any bubbles from any cylinder = Cylinder pressure into cooling system = Bad head-gasket, or worse.

[pojawis]

Thanks. Ordered test unit and awaiting delivery.

[pojawis]

Tested and confirmed leakage. Top end overhaul underway. Heads measure out at .022, so they'll be redone. Will do water pump and timing chain as well. This may belong in a separate post, but anyone have any recommendations on water pumps? More specifically, any particular brand to avoid?

Thanks.