mark thompson

Hello,

My name is Mark and I am fairly new to the 928 enthusiast world. I have a 1987 S4 5 speed that I purchased about 2 years ago. The car is in prestine condition with 120,000 miles and I drive her like an old timer.

Well, today I noticed a leak coming from the pasenger side of the car that looked brown with tan color on top. When I inspected the stain, it felt like oil. So, I put the car up on ramps removed the under carraige panel and found where the leak is coming from. There is a resevior at the back passenger side of the engine compartment. Is this the coolant resevior? And why is the consistancy of the coolant so thick. Please tell me that my oil and coolant are not mixing!!??

Well, my car is running fine...No warning lights...Not overheating....The oil dip stick looks normal. I am afraid to start it fearing that if there is trouble that I could make it worse. Can anyone help??

Garth S

That is the location of the coolant reservior/expansion tank: without speculation, would you remove the coolant cap ( "radiator cap") and report on the contents?
When was the antifreeze last changed?

mark thompson

When I removed the cap...I see a brown thick liquid. Looks like the foam of a cup of hot chocolate( hope this helps). The radiator has not been flushed since I've owned it. My neighbor was the original owner and he had the radiator replaced prior to me purchasing by Neillo BMW/ Porsche . For the past two yrs it has ran really really strong with no problems.

Mark

jeff jackson

OH - MY...this sounds NOT GOOD. I hope for you're sake this is due to a longterm lack of maintenance...and this is NOT an accumulation of engine oil, developing in the coolant recovery tank. This would indicate a blown head gasket...or...a cracked cylinder head. Does the car RUN OK ?? if so...you might "just" be ucky. if it has performance issues...maybe NOT so lucky...

mark thompson

The car runs excellent....No smoke no oil burning...It runs really strong...Let me ask you a question...When I change the oil, should the oil look the same? Or would it not be affected?

SharkSkin

Dip something like a pencil into the foamy stuff, then put it in a bucket of water. Do you see an oil film on top of the water? Does the oil on the dipstick look milky at all, especially when cold? If yes to either one, you may have a headgasket leak.

Leaking of oil into coolant but not coolant into oil could be a leaking oil cooler(located inside the radiator).

Richard S

Where are you located? Niello in Sacramento? I'm in Elk Grove and could help if you are local.

Rich

mark thompson

Thanks for your reply Sharkskin. I dipped the pencil in the resivior and put it into water and did see an oil slick on top. When I checked the oil dip stick, it looked normal with clean oil on it.

mark thompson

I am located just on the west side of Sacramento in Rocklin, Ca.

Garth S

I suspect that the oil cooler in your rad has let go .... allowing oil into the coolant: I would disconnect the two oil lines to the rad end tank ( driver's side) and have a pressure test placed on the coolant system.
If the oil cooler is perforated, coolant should flow from the lower oil line connector ..... If so, the repair is obvious, as is a flush of both oil and coolant ( when shutdown hot, the coolant pressure is higher than the oil system .... allowing coolant into the sump - the reverse is true when running).

mark thompson

Thank you very much. I will have the shop look at it.

Fogey1

mark thompson wrote:
"The car runs excellent....No smoke no oil burning...It runs really strong...Let me ask you a question...When I change the oil, should the oil look the same? Or would it not be affected?"


Somebody will correct me if I'm wrong but I believe there are several possible cylinder head gasket failure modes depending on the precise location of the fistula and the realtive pressures on each side. I'm not sure how/if inevitable one is after another. None are trivial, but some can go longer than others before running is affected. They can also overlap.

In decreasing order of seriousness/immediacy:

1) Loss of compression in the combustion chamber. The car will run worse and leaking hot gases at high pressure will quickly erode the gasket further (at least as long as the cylinder fires, which may not be too long) and may erode the head or cylinder walls. $$ -$$$$

2) Loss of sealing integrity between the lubrication and cooling system - water to oil. The engine will still run all right, but this is right up there with #1, because water in the oil can destroy the bearings in the bottom end and throughout the engine, especially as the coolant "drains," the crankcase overfills and the car overheats. This will give you a similar chocolate frappé, but on the dipstick and in the drained oil. $$ - $$$$$

3) Loss of sealing integrity between the lubrication and cooling system - oil to water. This will give you the chocolate frappé you've got in the coolant, but ... I've seen a few cars that ran for thosands of miles with a small oil to coolant leak. Unless/until it gunks up the cooling system, the car will run well. This failure can escalate quickly and unpredictably to #1or #2, but ... sometimes you can get lucky with a re-torque. $-$$$$$

#1-3 can occur in any order, overlap or happen all together.

Having said all that, you have a high performance engine, not an understressed American V-8. And it's much more expensive to repair after a catastrophic failure. I'd be changing the oil and coolant and doing compression and leak-down tests ASAP and not drive it much in the meantime

Though there have been threads here about Barr's Stop-Leak and other coolant leak treatments. You pays your money and takes your chances.

Good Luck.

jeff jackson

There you have it and there you are..Thanks Garth...this is good info for ALL 928ers with the oil cooler in the radiator...Lots of times its hard to assess the condition of the coolant in the expansion tank just due to age of the tank..and interior discoloration. BUT...if anyone notices the film on the surface as Mike reported (engine runs great...no smoke , etc.)... Methinks Garths observation is the likely culprit..

Mrmerlin

Hi I would add that since you found a oil leak into your coolant system it is imperative that you replace all of the coolant hoses after the leak has been found and the system has been flushed and the oil leak fixed, other wise you will be on borrowed time the oil will weaken the rubber hoses from the inside and one of them will eventually split. The most important hose to do is the one that comes from the engine to the heater control valve, follwed by the big and small radiator hoses , plus it might be a good idea to replace the heater control valve as the oil also weaken this plastic part where it is clamped into the hoses, Goodluck,........... Stan

RngTrtl

I am hoping for you that it is the oil coller in the radiator, I had this EXACT same thing happen to me except that I did not have a leak, but just oil in the coolent. Odds are good that that leak arose from the oil in the coolent line under the coolent resevoir and began to leak because of it. After you get it all sorted out, be sure to not only replace all the coolent hoses but also to pull the coolent resevoir and throughly flush it out (I used about 1/4 can of spray engine cleaner (GUNK) and shook it around for several minutes and then washed it out good with a hose). I have found that alot of the oil will adhere to the inside of that tank. I got my fingers crossed for you that it is the oil cooler and not a larger problem that Fogey1 aluded to earlier.