2005 525i N52 lots of oil in coolant, compression is ok, no coolant in oil

[reegz]

Hi guys new to the forum and BMW ownership, I bought 2 525i's and the 2005 with N52 engine I bought knowing it had engine issue. seller said he was driving and got a warning saying it was hot and wasnt far from home and hasn't driven it since, I notice a lot of oil mixed to a thick coffee coloured cream in the expansion tank and figured a head gasket or breach of a seal in the oil cooler. dry compression test comes up with 125 most cylinders and a couple @ 140 from idle. Pretty sure its oil in the coolant not trans fluid, no coolant in the oil and upon pulling the oil cooler apart I couldnt see any obvious breach between the seal. Can anyone tell me where else in the engine oil would mix with coolant? I suspected maybe the previous owner topped up oil in the expansion tank by accident but the oil doesnt look fresh it looks used (some areas are coffee cream other areas I can see just unmixed oil.

Any Ideas?

[MarcoZandrini]

The oil has mixed with the coolant. The head gasket is bad regardless of the cylinder pressure tests. Sorry.

[bmwdirtracer]

Welcome to the forum.

You can't diagnose a bad head gasket with a compression test. A leak down test, with the engine at full operating temperature, and using 175 psi of air pressure, and with the cooling system full to the brim, and open, is your best bet

Alternatively, if you bring the engine to full operating temp with the cooling system closed, and then you let it sit until the next morning, and the cooling system is still pressurized, you have a blown head gasket.

On a similar '07 N52 that my boss bought, I found that the expansion tank was a milkshake, and I changed the oil filter housing gasket and the oil / coolant heat exchanger gaskets, then flushed the cooling system with hot water, three times. I also changed the water pump and thermostat, because there were codes for the waterpump drawing too much amperage.

The car was just fine after all that; no blown headgasket.

[reegz]

I am hoping it is just the heat exchanger seals or a failure within the exchanger, I will pressure test it tomorrow, did you notice any obvious signs where the breach occured within the gasket/seal just before you put the new seals in?
with your comment about the cooling system still being pressurised in the morning I had noticed this with the other 525i I purchased however I havent had any power or overheating issues with this one.

[reegz]

Think I found the issue, upon pulling the rubber seal between oil heat exchanger and oil filter housing it looks like oil was making its way into the water port underneath the seal where it sits in the groove, I will attempt to clean it all up then flush out the system and put it back together with new seals and see how I go.

[reegz]

ok I'm talking to myself here but I will update for persons in the future who may encounter the same issue, I chose to ignore MarioZandrini's ill advice since although I am no expert I do know that oil in the radiator does not unequivocally mean the head gasket is blown.

I wasn't 100% convinced that the sheer large amount of oil in the radiator was purely from the seal between the oil and coolant channels as it didn't look that bad, so I tested the oil cooler by sealing one inlet of the coolant channel and blowing compressed air into the other inlet, I instantly noticed bubbles come out of the oil port so it seems the breach was inside the oil cooler. Glad I tested it now, new cooler is on its way.

[reegz]

Update, put the new oil cooler on and flushed all the oil from the system over a few weeks and about 10 flushes, using mostly dishwasher powder in the water each time. it was a messy time consuming job I eventually found it easier to start the car with the water pump running and diverted (and disposed of) the water that flowed through the pipe back into the expansion tank as it come through hot and bought alot of the oil and crap in the system with it helping clean the system faster .I topped up the tank with warm water as I went, this was more efficient than filling with soapy water, driving a while, draining then repeating.

Anyway the car runs sweet now and no oil getting in the coolant or vice versa.

[dworthy]

I for one will thank-you for keeping the tread updated. It is good to see that it wasn't the headgasket, and just the heat exchanger that was faulty. I will keep this in mind if I do see the same thing later on down the road as these cars are aging.

[MIKYZZ4]

Yes, thanks for the update.
Moral of the story: anytime others experience similar symptoms-
- verify whether your particular vehicle contains an oil cooler,
then check your seals.

[reegz]

Cheers for the kudos guys, I have relied on many forums to diagnose and repair all issues with my 2 bmw's often threads 7 years old have proved useful and I've come across a few threads where their car exhibits the same problems as mine but they never updated so I dont know what they did or if it fixed it so I think its important to update for other people who come across similar issues in the future.

[aktansrt]

The oil has mixed with the coolant. The head gasket is bad regardless of the cylinder pressure tests. Sorry.

Not true. Very uninformed diagnostics advice. The more likely culprits are, the breach in the double layer gasket between the oil filter, housing and the cylinder head. If that is OK, then possibly a breach in the gasket between oil cooler unit and the oil filter housing. If that’s also OK, it is possible that there is a crack in the oil cooler unit. If all of these are fine, then a possible issue with the head gasket might come in to play.

[bmwdirtracer]

Perhaps you will note that the OP got exactly the advice he needed on the very next post, and he followed through with that advice, for a successful result -- over five years ago. The success was noted and the thread was nicely wrapped up.

[marcva]

Thanks very much for following up with root cause and your solution. I try to pay back when I get help. this forum is a living database for the diehards that are trying to keep these cars on the road.

[aktansrt]

Perhaps you will note that the OP got exactly the advice he needed on the very next post, and he followed through with that advice, for a successful result -- over five years ago. The success was noted and the thread was nicely wrapped up.

That’s right. But this thread may also serve others that come here with the same symptom, but due to a different root cause. My response was to help those folks, not to belabor a point.