Coolant overflow reservoir contaminated with oil

[neimis]

Topic says it all. I've been trying to figure this out for years, I'm finally convinced it's engine oil. Car is a '92 Passat with the 1.9 litre IDI. I think it accumulates in the reservoir because that is the highest point in the cooling system.

What are all possible ways oil could find it's way into the coolant? Oil cooler? (has been pressure tested, shows OK) Head gasket? (compression is good, no steam ever in exhaust, no need to top off coolant).

I need to fix this problem once and for all before I change out the thermostat, install a new thermoswitch and flush the coolant system, etc.

Any help and ideas appreciated.

 

[GoFaster]

Oil cooler or head gasket.

If the head gasket leak is between a high-pressure oil passage and a moderate-pressure coolant passage, but the "fire rings" around each cylinder remain sealed, you'll have the problem you describe. Nothing can leak to the outside world, but you can get cross-contamination of the engine oil and coolant.

Very slow leaks don't always show up on pressure tests. Sometimes those gaskets can leak when the engine is hot but not when it's cold, or maybe when there is lots of cylinder pressure but not when there is little cylinder pressure, etc.

 

[neimis]

Thanks for the reply, Brian. (It's Brian, isn't it?)

I guess if I'm going to be doing the old "dealer routine" (ie. keep replacing parts until the problem goes away

) I may as well start with the cheapest. That would be replace the oil cooler, flush and refill coolant and observe the results.

Is that the recommended course of action?

 

[dogbreath]

When this happens with our big trucks 90% of the time its the oil cooler. Oil system is under mch higher pressure than coolant system- so oil migrates towards low pressure if there is a leak.

 

[SoTxBill]

usually its there because somebody overheated the car.. and warped the head.. and most likely a head gasket alone will not fix it.

but,, maybe you will be lucky and find the oil cooler at fault..

are your sure someone didnt put some bars-leak in the system.. its does look about the same. (wishful thinking)..

good luck bill

 

[weedeater]

Automatic? Then try the tranny cooler.

 

[neimis]

Car is a manual transmission, and I have owned the car since new; never had any radiator leaks or problems and never put in a "stop leak". So it's down to head/head gasket or oil cooler, I guess.

Thanks for all the replies.

 

[jag60mk2]

One other problem with this type of leak is the oil will eventually weaken all your coolant hoses.(voice of experience on Mopar 318 oil to coolant leak

)

Matt Ross
1997 Passat TDI

[ February 12, 2003, 22:59: Message edited by: jag60mk2 ]