Oil in coolant...

[Justin_FL]

I was going over the M5 this morning on my day off, preparing to change all the fluids since buying the car (car sat garaged for almost 2 years). Well peeked inside the coolant resevoir since it looked rather dark and noticed a nice layer of frothy oil on top. At least it appears to be oil as it was layered on top of the coolant and is brown, coating my finger. Did not notice this two weeks ago and when inspecting the car a month and a half ago before purchase.

Normally this indicates a blown head gasket, or maybe worse for the S38? I was expecting to rebuild the head because of the mileage (187k) but not so soon. Oil looked perfectly fine and I didn't notice any coolant while changing it. I was going to pull the plugs and get compression numbers as a baseline today as the previous owner said #5 or #6 was lower than the others so I could monitor during my ownership. The last few times I've driven the car it has been in the 90s and it always ran at 12 o'clock when warmed up.

Too bad I have no time to dig into it for a few months until the weather is cooler. I'm really missing my 535i and driving an E28!

[monty23psk]

Do a coolant flush to make sure. Maybe it just needs some clean fluids. Are you losing coolant?

[scottiesharpe]

Don't worry about oil in the coolant;

worry about coolant in the oil.

How does your oil dipstick look?

[Edit by scottiesharpe on [TIME]1123616452[/TIME]]

[Justin_FL]

No the car did not use coolant in the past 200 miles (as much as I've driven since buying) and the oil looked perfectly fine, needed a change but not full of water. The car had the green coolant in it which is what prompted me to change it. After finally getting to the drain plug on the block the greenish brown coolant made one hell of a mess because of the heat shield creating a waterfall and about 1/3 missed my bucket. Looks like the previous coolant before last was the red stuff which was causing chunks of nasty brown residue to form. Wonder how much damage this green stuff has done!

Looking at what fell on the driveway, I saw some oil sheen floating on top of water but that very easily might have been crap sitting on the concrete. I'm going to refill with water and check again after my next drive before wasting new coolant.

[monty23psk]

Put the blue bmw stuff in it. Hope it was just dirty coolant.

[Justin_FL]

Just thought I'd post a followup:

The stuff floating in the expansion tank must have either been rust or broken down coolant or both. Everything has looked fine the past 2 weeks after some aggressive flushing and removing the radiator for cleaning.

So I got all worried for nothing

[Steve Haygood]

Great news Justin !

[alpinass]

Replace that ugly old yellowish-brown expansion tank too. NOBODY EVER DOES! I can count the folks that have....maybe 10! The rest don't want to be bothered - If it ain't broke - don't fix it! Say that on a 100degree day - running the A/C full tilt- while sitting in traffic and your tank explodes! The best $45 I spent!!!!!