oil in the antifreeze & overheating

Oil in the coolant and overheating. Rough running.

Limber up your engine stand and toolbox. It's top end overhaul time.

Oil in the coolant- very rare with a bad HG but I've seen it 2-3 times. The block has an oil pressure passage on each bank going through to the cylinder head, and if the head gasket fails just right, it can be pumping oil into your coolant passages. Check for any unusual oil leaks as well between the engine and tranny- a bolt failing in this area can also cause what looks to be a bad rear main seal, when in reality it's just the HG/bolts.

Also, you don't have the oil cooler option on your DTS do you? I don't think any Devilles/DTSs ever had the engine oil cooler. Not that i know of. If you do, it could be a corrupted oil cooler in the rad. Doubtful, but don't overlook it.

Seems like a lot of people are having problems after getting the system flushed/refilled. And it seems like there's a lot more 00+ cars beginning to fail. I'm doing a 2002 STS very soon and a 2003 STS is also on the waiting list now.

sub, thats kinda what i expected to hear :crying2:

97, i dont see any oil leaks, i dont think i have an oil cooler on my car...

guess its time to get dirty...

You do have an oil cooler. It is inside the right radiator side tank. I would bet that is where your oil & coolant are mixing.

so do you think the radiator is bad? :banghead:

From what I'm reading, that would be my guess.

Is it possible the guy who did the flush mistook the surge tank deposits from sealant tabs as oil sludge? If the cooling system wasn't purged properly after the flush could the overheat could have been caused by air pockets? Is the car continuing to overheat?

chubbyranger said:

Is it possible the guy who did the flush mistook the surge tank deposits from sealant tabs as oil sludge? If the cooling system wasn't purged properly after the flush could the overheat could have been caused by air pockets? Is the car continuing to overheat?

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That's a distinct possibility.

Damn, I'm always late on these things but my thoughts are right in line with most of the rest.

Deposits in the tank are probably from seal tablets, HG failure very very rarely allows coolant / oil to mix and seeing how it happened after a flush I'm also going to blame the radiator.

I don't know how many times we have to say around here, DON'T FLUSH anything just drain and refill. Don't flush the rad, don't flush the trans just don't flush because the next thing you're flushing is money.

97EldoCoupe said:

Seems like a lot of people are having problems after getting the system flushed/refilled. And it seems like there's a lot more 00+ cars beginning to fail. I'm doing a 2002 STS very soon and a 2003 STS is also on the waiting list now.

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I called that and everyone said I'm crazy. Guess the different "thread pitch" didn't work out after all. :alchi:

chubbyranger said:

Is it possible the guy who did the flush mistook the surge tank deposits from sealant tabs as oil sludge? If the cooling system wasn't purged properly after the flush could the overheat could have been caused by air pockets? Is the car continuing to overheat?

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i dont know, i will talk to the guy that did it today. when i picked up the car it was fully warmed up, the gauge was at 12 o'clock as it usually is. i got about 5 miles down the road before it started getting hot.

i havn't drove the car since i brought it home. kinda waiting to get info on what could of happened before i tried to fix the problem.

one more thing, dont know if its related or not but, sometimes this last winter when the car was fully warmed up and i was at a stoplight the heater wouldnt blow warm air, but when i got going again it would blow warm again. anyways, dont know if thats related or what...

A heater core which gets cold at idle and warm at speed is a sure indication of air or partial blockage in the coolant or piping. With the car running, warm, in P and the heater on, temp at max, if the air then cools down at idle, try bringing the rpm up to around 2,000 for 30 seconds. Does the heater get warm ?? Where does the temp gauge go during this experiment ??? Can you hear any coolant flow (gurgling) down in the console area ?? If your heater heats and cools with rpm and you can hear coolant flow, then the chances are that you have low coolant, air trapped in the system, or maybe a bad thermostat. A failed head gasket puts combustion gasses into the coolant system and overpressurizes it, so coolant blows out the cap pressure relief and the engine overheats.

submariner409 said:

A heater core which gets cold at idle and warm at speed is a sure indication of air or partial blockage in the coolant or piping. With the car running, warm, in P and the heater on, temp at max, if the air then cools down at idle, try bringing the rpm up to around 2,000 for 30 seconds. Does the heater get warm ?? Where does the temp gauge go during this experiment ??? Can you hear any coolant flow (gurgling) down in the console area ?? If your heater heats and cools with rpm and you can hear coolant flow, then the chances are that you have low coolant, air trapped in the system, or maybe a bad thermostat. A failed head gasket puts combustion gasses into the coolant system and overpressurizes it, so coolant blows out the cap pressure relief and the engine overheats.

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i'll try this tonight. i have had the car almost 2 years and havn't added coolant to it. every time i checked it it was where it was supposed to be. i have never heard gurgling from the car before. last winter it would cool off when idling and once you got over 1000 rpm it would warm up again. i have to check it out and get back to you. thanks all for your help...

See now this is the issue I have going on the 4.5 forum. I thought for sure there was a clog somewhere but there's not. Now we're swearing that something is wrong with the water pump. This is on a 4.5 but same symptom.

I also keep getting told that a clogged heater core will not cause a car to overheat because of the bypass.

Maybe we can work this out together? Have any of you participated in my 4.5 posting?

I also keep getting told that a clogged heater core will not cause a car to overheat because of the bypass.

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That is correct. It will only cause a lack of cabin heat.

OK So I'm definitely dealing with a flow problem then, as we're discussing.

Ranger said:

That is correct. It will only cause a lack of cabin heat.

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ok, finally got a chance to "play" with the car last night.

i started off by removing the hoses that went to the overflow tank and made sure they were clear. all were ok. then i took the radiator hose off and added 2 tablets of bars leak, reattached the hose and topped off the overflow tank. it took about a gallon to get to the cold mark. i started the engine and ran it for about 1/2 hour and the coolant temp was 198 according to my obd2, but the bottom radiator hose was still cold. it was blowing cold air, i rev'd it up to about 1500 and it started to blow warm air and continued to do so. so i took a walk with my son and came back after running it for about an hour. the hose was still cold and the temp was the same, 198+-. both fans were running by the way.

what temp is the thermostat supposed to open at? could that be the problem?

I believe the thermostat starts to open at 180. Sounds to me like you have air in the system or are not purging it all out. Rev it to 3-4K a few times to purge it.