[Breakfirstfinishlast]

Hello everyone,


I posted a while back about oil getting into my coolant res tank. I consider myself a fairly good mechanic, so normally I would be fixing this stuff myself, but I still had a dealer warranty on the car, so I took it to BMW to have it fixed. They told me the OFHG was leaking. They replaced the OFHG and the cooler gasket, flushed the coolant several times, pressure tested it again, changed the oil and sent me on my way. They also told me that there was still some residual oil in the system that they couldn't get out completely...

Fast forward to last night. My coolant light comes on. I pop the hood and its a coolant massacre inside. The upper rad hose that runs into the OFH popped a small hole. Np, I told myself. I went and bought a new upper coolant hose...

When I went to replace the coolant hose, I noticed that there was a TON of fresh looking oil in the hose. I tried to clean it out and took it for a spin. Then I checked in the coolant res and there was a lot of oil inside again. I took it back to the BMW dealer and I am now awaiting news..

Really bummed out about this because im going to see NASCAR at Watkins this weekend and I really wanted to take the car up there to rip up some backroads up in the Finger Lakes.


My question is.. what the hell do you think is wrong with it? Its not running weird as if the head gasket is blown or anything. It just seems like either they didn't make an attempt to get the oil out of the cooling system and it built up in the until the oil ruined the coolant hose, or there is still an OFHG problem that they didn't address properly. Im getting pretty nervous about this car. I love it but its been nothing but a pain.

Thanks!

[atek]

Only way to tell at this point is to perform a compression and leak-down test to see if it really is the head gasket or something else.

Fresh oil in the coolant is never a good sign, especially after driving. Lets hope for the best, though.

[NotThatDallas]

@Breakfirstfinishlast I just finished living through this exact same scenario.

Picked up a very clean 2016 M235i at the end of April that had, best my mechanic and I could tell, no issues. After a fun day in the GA mountain back roads, the low coolant warning came on and when I stopped to check it, the reservoir was full of engine oil, which of course got my attention.

Sparing you the details of how many trips to my local BMW indy shop this took the order of diag and repair went something like this:

1. Check and repair usual culprits: replace OFHG, check oil thermostat for issues
2. Leak down testing, checking coolant for exhaust gases (trying to rule out head gasket)
3. Flushing coolant system after first round of repairs
4. Continued oil in coolant
5. Eventual success in replacing the oil/coolant heat exchanger
6. Lot's more flushing of coolant system

#5 was a surprise to my indy shop. They had checked the heat exchanger and thought they ruled it out, so when that repair was the ultimate fix, there was a lot of apologies/head scratching.

It's been 2 months since that repair, and after weeks of commuting/backroad driving and even a HPDE, there is only trace oil in the expansion tank that I sop up with a paper towel once in a while to try and preserve the o-rings from swelling.

I can provide more detail if you want, but that's the quick summary.

[Breakfirstfinishlast]

Originally Posted by atek

Only way to tell at this point is to perform a compression and leak-down test to see if it really is the head gasket or something else.

Fresh oil in the coolant is never a good sign, especially after driving. Lets hope for the best, though.

Thanks for the response! I got a call back from the BMW dealer and they informed me that they pressurized the cooling system and found no leaks.. Im not sure if that is an accurate gauge of what could be wrong, maybe its holding pressure in the crankcase? Not sure. But they seem to think nothing is wrong with it. I guess it just needs more flushing? I paid them $1200 to do the gaskets and clean the cooling system, but they didn't even come close to touching all of the oil in there.

[Breakfirstfinishlast]

Originally Posted by NotThatDallas

@Breakfirstfinishlast I just finished living through this exact same scenario.

Picked up a very clean 2016 M235i at the end of April that had, best my mechanic and I could tell, no issues. After a fun day in the GA mountain back roads, the low coolant warning came on and when I stopped to check it, the reservoir was full of engine oil, which of course got my attention.

Sparing you the details of how many trips to my local BMW indy shop this took the order of diag and repair went something like this:

1. Check and repair usual culprits: replace OFHG, check oil thermostat for issues
2. Leak down testing, checking coolant for exhaust gases (trying to rule out head gasket)
3. Flushing coolant system after first round of repairs
4. Continued oil in coolant
5. Eventual success in replacing the oil/coolant heat exchanger
6. Lot's more flushing of coolant system

#5 was a surprise to my indy shop. They had checked the heat exchanger and thought they ruled it out, so when that repair was the ultimate fix, there was a lot of apologies/head scratching.

It's been 2 months since that repair, and after weeks of commuting/backroad driving and even a HPDE, there is only trace oil in the expansion tank that I sop up with a paper towel once in a while to try and preserve the o-rings from swelling.

I can provide more detail if you want, but that's the quick summary.

I would be interested in talking more about this subject. I got a call from the BMW dealer and they told me that the cooling system is holding pressure. In your experience, was a cooling system pressure test enough to determine that there was some type of issue going on? Or did they have to do a cylinder leak down test? I guess a leak down would only really determine if there is cylinder/head gasket leakage..

I guess im just a little big skeptical because the first time I took it in when I found oil in the coolant, they told me that there was nothing wrong with the car even though there was.

[NotThatDallas]

Originally Posted by Breakfirstfinishlast

I would be interested in talking more about this subject. I got a call from the BMW dealer and they told me that the cooling system is holding pressure. In your experience, was a cooling system pressure test enough to determine that there was some type of issue going on? Or did they have to do a cylinder leak down test? I guess a leak down would only really determine if there is cylinder/head gasket leakage..

I guess im just a little big skeptical because the first time I took it in when I found oil in the coolant, they told me that there was nothing wrong with the car even though there was.

My indy shop pressure tested the coolant system and it tested fine. They did locate a crack in the expansion tank, so they replaced that during the first repair attempt.

First repair was OFHG, lots of diagnostic testing of coolant system, and they pressure tested both the oil and the coolant sides of the heat exchanger. Lots of coolant flushing.

After the first repair attempt the oil was at a problematic level in the coolant system within about 2 days of normal use of the car, under 4 operating hours.

The second repair was replacement of heat exchanger. Between what the shop told me after repair and my own experience, I think the heat exchanger was the problem all along, the higher pressure present in the oil system is why the oil was found in the coolant, not vice versa.

They did perform a leak down and compression test the second time to rule out head gasket damage. I recall they also tested coolant in some way to detect exhaust while the car was at operating temp.

[XutvJet]

The heat exchanger makes the most sense. If I had this issue, that the first thing I'd be looking at. The mixing of coolant and oil from a failing OFHG is possible, but I've never heard that happen and the biggest issue with a failing OFHG is the exterior leakage of oil.

[overcoil]

And I think there was a heat exchanger leak problem posted on this site a year(s) back, similar symptoms.