320d Oil leaking into expansion tank

[wans]

Hi

 

I bought a 2011 BMW 320D 6Speed Manual used a few months back. It has 130k miles on the clock but has a full service history from a BMW main dealer.  She is a beauty, but needs some TLC, probably an ex rep car I'm guessing but got it for a steal (or so I thought).

 

Anyway got the car and checked fluids only to find the expansion tank full of black oil as if it was pumped straight from the sump, not frothy or milkshake like, straight up dirty oil. The oil cap and dipstick were however, froth free. After a little google-fu the common denominator seemed to be a failed oil cooler or oil cooler gasket which of course are dealer parts. Upon inspection the oil cooler gasket had some visible tears in the seal but I figured id throw in the brand new cooler too as a precaution.  Also removed and cleaned all the pipes and ran a flush of pure orange juice through followed by a rad flush solution (cant remember of hand which one but it was wynns, so fairly reputable brand). Dropped the old oil out and replaced it while it was up on the ramp also as a precaution.

A few days later and I notice some oil on the floor, checked expansion tank and found it full of oil again.

Bit more google-fu and a call to the dealers to order an oil filter housing gasket and back on the ramps she goes. When this was stripped out the gasket looked fine, if a little compressed, but threw in the new one anyway. Pipes off again for cleaning, and flushed a couple more times, got lots of thick creamy goop out of the heater matrix and rad but eventually everything seemed to be running clear with only the odd spot of grey oil/water mix coming through.

 

Opened the expansion tank this morning to find my good friend the dirty oil is back. Sat on the top of the expansion bottle giving my the finger.

The car does not smoke

The heaters are working gloriously

The car pulls like an absolute train

I'm at a bit of a loss, it would indicate either a crack in the block or a blown head gasket... but I would have expected creamy sludge on the dipstick and under the oil cap if that was the case.

my next move is to probably get the block pressure tested but I'm wondering if this would be able to isolate between a head gasket or a crack?

Are there any other seals and/or gaskets that are prone to fail that would give these symptoms?

Any help would be much appreciated guys and gals!

 

[Bimmer Owners' Club]

Hi Craig...welcome to the Forum

Sorry to hear you're having such bother already.

If it was me attempting to diagnose the fault, I would first run a Leak Down Test (introducing compressed air into the cylinders and seeing where it is escaping from). If you put the cylinder being tested on BDC and remove the rad cap, if there are air bubbles in the coolant then you have a cracked cylinder liner or head gasket if the piston....try it also at TDC. Repeat for all cylinders.

If the air is escaping through the inlet or exhaust then it would be valves or if it is coming out of the oil filler cap it would be piston rings.

Saves a huge amount of stripping down to establish exactly where the problem is.

Let us know how you get on with it

Cheers  Trevor