I'm hoping someone can help me narrow this one down....

I have a 1998 Camaro, automatic trans., 3800 series II. 160K mi. The other day, I went to check the coolant level in the overlfow bottle, and found a black oily sludge on the dipstick. The same black sludge was on the underside of the radiator cap, and thinly coated on the thermostat. I replaced the thermostat back in April or May, so this is a relatively "new" problem. The car has the universal green antifreeze in it; not DexCool. Both the crankcase oil and transmission oil look clean and normal. Levels are good. I added oil to the engine the day before I noticed the sludge, but the engine has always had a slight exterior leak.

A google search on the issue brought a slew of posts on various forums with people all insisting that oil in the coolant always means a head problem (gasket, cracked, or something horrific like that). However, I don't have any poor drivability symptoms.

I also noticed some antifreeze pooled up on top of the intake manifold near the middle fuel injector on the driver's side of the engine.

I haven't flushed the coolant system yet, and am afraid to drive the car without knowing how oil is getting into the coolant system. Does anyone have any ideas on this one? What should I check?

Here's a recap of the symptoms:

- black (not brown, red, gray, or orange) oil in the coolant.
- black, oily sludge accumulated in overflow bottle and radiator cap. Oily film on recently replaced thermostat.
- no coolant in the engine oil/crankcase.
- transmission fluid appears coolant-free and at the proper level.
- coolant pooled up (small amount) on top of intake manifold near the middle fuel injector on the driver's side of engine.
- car runs as well as ever; does not overheat, accelerates well, idles well, and emits normal exhaust (no white smoke or other vapors).

 

only a few places it could be coming from. cracked head or block come to mind. i dont think the intake has coolant going through it so im not sure how that coolant is getting there. there is coolant going through the front timing cover though and being you just where messin around up there i would suspect that first.

 

Lim gasket? Coolent goes thru that. I just went thru this myself. I have a 98 v6 camaro. I just did the upper and lower intake gaskets. You gotta rePlace the crappy plastic low intake gasket, it's prolly leaking google that problem. I have a full q&a over on v6fullthrottle with pics! It's really easy to fix you can do it over a weekend.

 

so its leaking from the lower intake manifold gasket and thats how its getting on there by the injectors. that makes sense. how about givin the guy a link or transfering that info here and we can stick it.

 

With the 3.8 intake gasket is the most common antifreeze issue. There was a class action law suit against GM for it. Your way late to get a pc of that.

Leaking to the intake and into the oil is pretty common. You need to not drive it and get that coolant\oil out of the engine ASAP. Coolant is like paint stripper to bearing babbit. With high enough volume it can trash your motor in hours.

Here a pic showing the suspect coolant passages.

 

so far he is getting oil in the coolant only. thats a good thing. so gorn this is a way that the oil can be getting to the coolant, seems like it would need to be from a pressurized oil port?

 

My bad, the word dipstick messed me up. No there is no good way for oil to get into the coolant except a cracked block. There is no oil pressure in the head or intake. Most likely it is not oil. Most common issue would be a blown head gasket pushing “dirty” air/fuel into the coolant. Whenever you mix oil and coolant you get a brown milkshake look. Black is normally soot from the compression camber.

 

Ok I'll try to find it. But I'm telling you guys, I got the black stuff in the coolent and after a few more miles I started getting the light brownish milkshake looking oil. I changed the lim and upper and I put almost 8,000 miles on her now issues.

 

Thanks for the replies, guys.

I'm still not quite sure what's going on with this. I took a sample to work today in a bottle and showed a guy who worked for years as a GM technician; and the second he saw the bottle, he said "that is not oil." It looks like oil, feels slick like oil, but does not smell like oil (smells just like old antifreeze) and has a gritty feel to it. Based on that, and what the mixture did when he shook it up, he said without hesitation that it was just really badly neglected coolant. He also said that it looked like there might be old Dexcool mixing with green antifreeze in the mixture, but that the bottom line was that he does not think that the stuff in the coolant is oil at all. To better troubleshoot this, he is bringing a tool to work for me tomorrow to pressure-check the cooling system.

Hopefully his theory isn't too good to be true...we'll see what the pressure check shows tomorrow.

 

That's kind of what I was thinking, remnants of Dex-cool mixing with the green. Get it flushed and cleaned out. If the intake gaskets haven't been replaced in 160k miles, those are way overdue as well.