Just noticed what appears to be oil in my overflow tank! The car has the 3100 engine. It looks like brown, used oil look. Has anyone had this issue before? I am thinking it may be a head gasket. I would like to flush the system, but not if this is truly oil. Any help would be appreciated! Thanks!

 

Your lower intake manifold gaskets blew. You'll want to replace them with FelPro aluminum gaskets not the plastic crap like what's in there currently. 3100 and 3400 engines are notorious for this problem.

 

Are you sure the intake gasket is the issue?

 

Most likely that is the issue......

 

If it was the head gasket you'd also notice a higher than normal running temp or even overheating, and you'd notice steam out the exhaust from coolant leaking into the cylinders.

I'll add I had this problem on mine and my gasket was completely cracked. It had close to a half inch space and the oil rotted a hose and I had oil dripping down onto the frame. All because mine went un repaired - I had my suspicions they were bad when I bought the car, but didn't look much into for a while and that was the end result.

 

My vote is what Mike 00LS said, lower intake. Go Fel-Pro aluminum gaskets and kiss the problem bye-bye.

 

This is my sons car and he has mentioned it tends to start to over heat in stop and go traffic. Most intake manifolds only have fuel and coolant traveling through them, is this not the case with the 3100? I have not had a chance to check out the repair manual to see how the engine is configure internally. I'm just wondering, if I have it apart to the point of the intake, should I go one step farther and do the heads as well? Thanks for all your help thus far!

 

I can almost assure you the LIM Gasket is bad, but being a 3100, there is a good chance that the head gasket is also bad. The 3100/3400 is notorious for both gaskets failing at some point.

 

Well if it's starting to overheat then like mamonte said both might be going bad. Once you tear down to the LIM gaskets, the heads arent much further, so really it wouldn't be that much more difficult to just to both.

 

The overheating could be a result of the low amount of coolant resulting from coolant leaving the engine, mixing with oil, ect.
The LIM gaskets for the 3100/3400 move air/fuel mix and coolant. The coolant ports on the outer sides of the heads. If you get a radiator pressure tester, you can bump up to 13lbs of pressure, listen for hissing, odds are you'll find a leak with the LIM gasket travels.

If the heads are bad, you can get white clouds from the exhaust (that's the coolant burning up) and sometimes people notices a "sweet smell". ALSO, the car may experience being over pressurized (the gases from the cylinders will fill the cooling system beyond what it should hold. When my 3100 blew it's head gaskets, I did not get clouds until the end and I was confused as heck why I was constantly bleeding air pockets. I would pull over on my commute to work and release the bleed screw while the car was running when it would start to "run hot". What was happening is the car never "over heated", but the hot gases register hotter on the temp sensor then the coolant and it takes longer for the Tstat to open, once I released the air, the t-stat did it's thing immediately.
By the time I found my answer, the over amount of pressure blew the gasket on a side tank to my 1-2 year old radiator (I love life time warranty, replaced it with no questions asked).

If you are willing to do the work, there is NO harm spending a little extra time/money to go down to the heads. You're honestly not that far away at the point you do the LIM gaskets. You just need to make sure the decking surface of the heads is clean and STRAIGHT/FLAT before re-assembly. Some send the heads to a machine shop, in my case, I used a straight edge (not 100% perfect, but gives you a fairly good check for a street car).