[gm62]

I have a 2014 rwd 335i msport (83k miles) that's been mixing oil into the cooling system. A lot of it. I took a brake bleeder to the expansion tank and pulled out over a quart.
The engine tested 230 psi across all 6 cylinders with less than 10% loss, runs flawlessly, and the temps never dare to creep up.

After digging on the forums and from what I could find, I did the following:

I had the ofhg replaced, oil thermostat gasket replaced, upper radiator hose, thermostat hose, cheesy plastic overflow hose, and the expansion tank/cap replaced.
The coolant was flushed 3 times and the oil was changed (old oil looked fine.)
I got the car back last night and I've put about 130 miles on it. No funny business, car runs happy as can be. Kept an eye on temps in the hidden menu, nothing out of whack.
But there's still oil in the cooling system.
I expected for there to be residual, and planned to do a few flushes over the next couple months, but what I found today was more than just residual. It's very apparent oil is still getting in somewhere.
My problem is, if it's not the fabled ofhg, and compression is fine, then where?
My car looks like it has an oil cooler (much like I've seen on the housings of the 4cyl models) tucked directly underneath the coolant tank. Part number pulls up engine oil cooler. I haven't found much info about it online, or any diy's about replacing it.
Is there something inside that which could fail and cause this? It looks relatively easy to replace, but I don't know enough about these engines yet to know if that's true, or if I'm missing vital info about it (much like priming when doing the gasket) that could lead to me messing something up.
I'm nervous about replacing it and finding out it doesn't solve the problem, or blindly going into the repair and finding out it's a bigger task than I was ready for, or messing something up in the process.

Does anybody have any info on this? Part number is 17217628058.

I've been wildly stressed out about this entire situation for two weeks.
This car is still new to me and I've been physically ill dealing with what might be looming doom.
I really need somebody that's well versed with the problems to (I hope to god) shed some light on the situation, and these forums seemed like a good place to start.
Thank you in advance.




From today (after ofhg repairs):

[har8_f30]

When you changed the OFHG did you do both of them?

[n55david]

Probably the OFHG

[gm62]

I’ve replaced the ofhg already. Both ofhg, and the oil tstat gasket on the front of the housing.

[n55david]

Originally Posted by gm62

I’ve replaced the ofhg already. Both ofhg, and the oil tstat gasket on the front of the housing.

Yes, thats long been established. And I'm telling you, there is a good chance that it's the OFHG

[gm62]

Originally Posted by Phantom10R

Yes, thats long been established. And I'm telling you, there is a good chance that it's the OFHG

The gasket that I just had a reputable shop replace two days ago would be the cause to the issue?
I’m sorry if I’m failing to understand.

[n55david]

Originally Posted by gm62

The gasket that I just had a reputable shop replace two days ago would be the cause to the issue?
I’m sorry if I’m failing to understand.

Yeah. So I don't know what happens or more so what didn't happen during the process but I've seen a good handful of posts here and on Facebook about the same issue. Nearly every time it's something related to the job that wasn't done 100% correctly. Now could it be something else, sure but I've seen this too many times to dismiss it.

[gm62]

Originally Posted by Phantom10R

Yeah. So I don't know what happens or more so what didn't happen during the process but I've seen a good handful of posts here and on Facebook about the same issue. Nearly every time it's something related to the job that wasn't done 100% correctly. Now could it be something else, sure but I've seen this too many times to dismiss it.

Would the cooler underneath the reservoir cause this problem? If I have to tear it apart and redo it I’m wondering if it’s worth replacing that in the process.

[n55david]

Originally Posted by gm62

Would the cooler underneath the reservoir cause this problem? If I have to tear it apart and redo it I’m wondering if it’s worth replacing that in the process.

No idea, never had to mess with it. I'd wait for one of the more "helpful" posters here to chime in.

[McGyv3r]

Start with a leakdown test on all 6 cylinders. This will help you decide if your head gasket is leaking to the intake, exhaust, cooling, or crankcase system.

If you're good on the leakdown, then there are only a few other places where the coolant and oil interface.

I'm assuming that you're reliant on a shop to fix it. It's going to cost money, but remember that you're paying them to diagnose and fix the car. Let them figure out how to fix it and don't just throw parts at it.

Good luck!

[F32Fleet]

Did the shop also replace the gaskets for the oil cooler? These gaskets are found at the connection between the oil cooler lines and the oil filter housing.

[gm62]

Again,I’d had the shop do a leak down test, and I’d had both gaskets replaced.
Ultimately everybody decided that It was due to failure of the heat exchanger underneath the coolant reservoir, and I’d purchased the part and planned to make the repair myself. But the company that sold me the car agreed to buy it back for full price and reimburse the full price of repairs to the car.
All’s well that ends well. Thank you for the help guys.

[Lazzaaroo]

Originally Posted by gm62

Again,I’d had the shop do a leak down test, and I’d had both gaskets replaced.
Ultimately everybody decided that It was due to failure of the heat exchanger underneath the coolant reservoir, and I’d purchased the part and planned to make the repair myself. But the company that sold me the car agreed to buy it back for full price and reimburse the full price of repairs to the car.
All’s well that ends well. Thank you for the help guys.

So how sure would you be saying it was the heat exchanger underneath the Coolant Tank?
Currently going though the same thing, both OFHG were replaced twice. Replaced entire OFH.
Compression tests were good and changed my oil with no coolant in it whatsover.
This would be the second time i hear of replacing the Heat Exchanger under the coolant tank.
Considering it isnt expensive I may just go ahead and try it out.

Kinda bummed you wont find out now since they bought your car back lol