99 Grand Prix SE 3100. Oil in coolant

[David Fulford]

175k miles

Well, I found some oil in my coolant today.

Just changed the oil and didn't see any coolant in there. Looked good. Went to check the coolant level and seen some floating on top. Also found some in the overflow tank. Not much, but enough to make me worry. The good news is the oil level was on the low end, but I didn't have to add any in between changes (~5kmiles).

I just had $800 of transmission work done last month so I want to squeeze as much out of this car as possible. It is also leaking coolant onto the ground when cold. Stops when warm. Also clattering quite a bit, especially when cold. No coolant smell in the exhaust. Converted to the good green coolant. DexCool is gone. So, how long do you suspect I can drive this before it let's go? I've read quite a bit about the intake gaskets causing this. Any step-by-step write ups on how to replace? I can do brake jobs and other small stuff. How hard would this be?

Getting about 26mpg. Runs fine.

I know nobody has a crystal ball. Just trying to get a feel for how bad this really is.

Thanks!

-Dave

[BNaylor]

Are you getting any oil in the cooling system since the changeover to green. Sounds like the lower intake manifold gaskets which is very common on 3.1L engines. It is not hard and can be done DIY. Try searching this GP forum for old and recent posts concerning "intake manifold" and "3.1". I recall newer and older posts. I'm getting ready to do a UIM/LIM job on a 3.4L myself which is similar.

[Doc Blazer]

Sound like you may need a new radiator. The transmission fluid cooling lines pipe the fluid into a side reservoir on the radiator seperate from the coolant. .Transmission fluid getting over into coolant . was a good fix on my T-Bird , Glad I found out before changing major engine gaskets.

[spacepiston]

I just fixed this problem on my car and I revised GTP Dad's how to for my car in this link:
http://www.automotiveforums.com/vbul...d.php?t=526875


I tried to include everything.. I can tell you that the noise you are hearing when it's cold is most likely due to the coolant in the motor. Mine did that and it got worse and worse as more water leaked in. Since I changed my intake gaskets it's all quiet again.

I would say you should change those gaskets this week. You will destroy your motor if you don't. It's $500 roughly if you pay someone to do it. I did it for $50 plus my labor.


Check your transmisson coolant lines for excessive rusting too. It's a common problem apparently.

[David Fulford]

Thanks for the replies guys.

The Dexcool has been gone since before I bought the car at 117K. I just noticed the "oil" in the coolant so I'm not sure how long it's been there.

Thinking more about this, it doesn't seem likely that a bad intake manifold gasked would let oil into the coolant circuit. Wouldn't there be more pressure on the coolant side rather than the oil side? If anything, wouldn't it be more likely that a bad intake gasket would let coolant into the oil? I am NOT a mechanic so this may be completely wrong. Just putting it out there.

Bad tranny cooler in the radiator is interesting. Any good ways to definitively diagnose that?

[richtazz]

pressure test the cooling system, and listen for where the leak is.

[Doc Blazer]

What you described sounds exactly the same as my high milage 91 T-Bird work car. I drained and flushed the system. Removed and replaced radiator.It cost me about 170 dols for a new radiator. Labor wise it is much easier and faster than changing eng gaskets. Radiators dont last forever, you just spent money on the tranny, why not get a new radiator. It worked for me.

[richtazz]

The failure prone area on the 3100 engine can allow coolant to go either way. Normally, coolant will leak into the lifter valley and contaminate the oil. I have seen were the opposite happens if sludge has clogged up the PCV valve and valve cover baffels. This lets pressure build up in the crankcase/lifter valley, pushing oil out into the leaking coolant passage contaminating the oil.