[ArenGh]

It's not the Valve Cover Gasket. I just replaced it and have done a thorough inspection around the motor with a mirror. It's all clean. I've also watched with a mirror with the motor running to make sure no oil is dripping onto the downpipe or o2 sensor.

Oil is bubbling at the o2 sensor. Any ideas what the problem could be?
The car is a stock X3 35ix with 72k miles.

Thanks!

[doodlebro]

That sounds like a failing turbo. Oil should not make it to the O2 sensor and be able to bubble out like that without serious issues with the turbo seals. I would triple check that it's not something else dripping into that area, the bubbling may make you think it's from the O2 sensor when that may just be a side effect of the oil dripping into a hot area.

[ArenGh]

Originally Posted by doodlebro

That sounds like a failing turbo. Oil should not make it to the O2 sensor and be able to bubble out like that without serious issues with the turbo seals. I would triple check that it's not something else dripping into that area, the bubbling may make you think it's from the O2 sensor when that may just be a side effect of the oil dripping into a hot area.

I'm about 95% sure nothing is dripping onto it. No white smoke is coming out the end whether at idle or under load. Are you still thinking it's the turbo?

Thanks

[Wgosma]

Excessive oil burnt in combustion chambers = blue tailpipe smoke. Motor has to be burning fair excess amount of oil for visible blue smoke to be seen. This typically occurs with worn piston rings and/or valves.

White smoke at tailpipe = water vapor/steam...cause is coolant in combustion chambers (typical of head gasket breach).

Do you have a feel for rate of oil loss?

I'd triple check around that VCG, etc. oil at the O2 sensor location seems unlikely to me to be coming with combustion exhaust gases.

[ArenGh]

Originally Posted by Wgosma

Excessive oil burnt in combustion chambers = blue tailpipe smoke. Motor has to be burning fair excess amount of oil for visible blue smoke to be seen. This typically occurs with worn piston rings and/or valves.

White smoke at tailpipe = water vapor/steam...cause is coolant in combustion chambers (typical of head gasket breach).

Do you have a feel for rate of oil loss?

I'd triple check around that VCG, etc. oil at the O2 sensor location seems unlikely to me to be coming with combustion exhaust gases.

I think I went through half a quart over about 6 or 7k miles. Very insignificant oil loss imo. I'm not seeing any smoke come out the tail pipe, white or blue or black.



The circled area is where oil seems to be starting, and it flows down to right above the 6pt section where it bubbles and flows onto the downpipe. I don't see any oil on that corrugated sleeve and I've held the mirror to see if anything drips on it and I'm not seeing anything.

Is it possible for oil to move upward against gravity while the car is stationary? Also, more oil accumulates and burns there when driving rather than at idle.

[Wgosma]

Is that a photo of THE sensor that is/was in your car?

The sensor threads into the exhaust manifold and is sealed with a metal crush type gasket/washer- see in the pic. So the oil is not coming from inside the exhaust manifold- it has to be dripping onto the O2 sensor's housing and/or attached signal wire (part of the signal wire is protected by aluminum sheath- heat shielding) from some other engine component/gasket that has a leak.

I'd bet your new VCG is leaking...it's not that rare to have happen. Sometimes it will only leak a drop or two when motor is pushed to accelerate.

[ArenGh]

Originally Posted by Wgosma

Is that a photo of THE sensor that is/was in your car?

The sensor threads into the exhaust manifold and is sealed with a metal crush type gasket/washer- see in the pic. So the oil is not coming from inside the exhaust manifold- it has to be dripping onto the O2 sensor's housing and/or attached signal wire (part of the signal wire is protected by aluminum sheath- heat shielding) from some other engine component/gasket that has a leak.

I'd bet your new VCG is leaking...it's not that rare to have happen. Sometimes it will only leak a drop or two when motor is pushed to accelerate.

Well this is the kind of reassurance I wanted. I'll go ahead and order a new valve cover as well this time. It's like pen ink, you never see it leaking then it's everywhere.

[Wgosma]

Valve covers are quite pricey; I'd only replace if you feel you likely damaged it (they are plastic and can crack) when you removed it last time; it's very rare they crack unless mishandled.

I'd opt to inspect it after removal and if looks good reinstall- do proper surface prep and you can reuse the new gasket, inspect it also.

[ArenGh]

Originally Posted by Wgosma

Valve covers are quite pricey; I'd only replace if you feel you likely damaged it (they are plastic and can crack) when you removed it last time; it's very rare they crack unless mishandled.

I'd opt to inspect it after removal and if looks good reinstall- do proper surface prep and you can reuse the new gasket, inspect it also.

I know they're kind of pricey but I think it's worth it just for the PCV valve alone. Also I'm pretty sure one of the corner bolt holes is cracked.

[Wgosma]

Then makes sense to replace.
Good luck/Bill

[doru]

Originally Posted by Wgosma

Valve covers are quite pricey; I'd only replace if you feel you likely damaged it (they are plastic and can crack) when you removed it last time; it's very rare they crack unless mishandled.

I'd opt to inspect it after removal and if looks good reinstall- do proper surface prep and you can reuse the new gasket, inspect it also.

Those plastic valve covers on these N5x engines do crack, especially on the boosted engines. On my 335is, the valve cover cracked in 2 places - I changed it at +/- 60k miles. Car was/is stock. Asked some questions around, and it seems a "normal" occurrence for the boosted engines to develop cracks on the valve covers (not normal in my books). On an older N52 X3 si (e83), I replaced the valve cover because it warped.

I think on these new N5x engines, the valve covers are thinner than the older counterpart on M5x engines. At least this is my take, once I pulled valve covers from N54 & N52 engines, compared to M54 valve covers, or N62.
German law forces car manufacturers to use recycled plastics, hence many issues with these cars since the turn of the century.

To check for warp, you need a 100% flat surface, then place the pulled valve cover onto it. Valve cover clean, then first go around with a bright flashlight and check on opposite side. If you see light shining through, it's toast. Some times one side could be ok, use gauges if not sure. But usually the warp is big and can be spotted with naked eye.

0.02

[gh335i]

I had the same problem with oil leak on the converter. I installed a new valve cover and cleaned everything off. (2012 335I ) it did look as if the valve cover was leaking / seeping. gasket was hard and flattened. since then I have had a phantom oil burning smell after a steady cruse. I didn't see any leaks at the cover. but the oxygen sensor is getting damp with oil at the same place you circled in your picture. I cleaned the area at the sensor and took it for a short drive and it was damp just enough to make a ring around the sensor. I was suspecting the turbo as the problem. did you solve your issue?

[ClampThurst]

Originally Posted by gh335i

I had the same problem with oil leak on the converter. I installed a new valve cover and cleaned everything off. (2012 335I ) it did look as if the valve cover was leaking / seeping. gasket was hard and flattened. since then I have had a phantom oil burning smell after a steady cruse. I didn't see any leaks at the cover. but the oxygen sensor is getting damp with oil at the same place you circled in your picture. I cleaned the area at the sensor and took it for a short drive and it was damp just enough to make a ring around the sensor. I was suspecting the turbo as the problem. did you solve your issue?

I noticed my F25 smoked for about 300 miles after the valve cover gasket job. It was left over oil from the leaking gasket(a few crevices keep all amounts of oil that drip onto the O2 sensor). I too was afraid that the valve cover was leaking still but it did go away.

[Barbera335]

I have seen oil pressure sensors fail and pump oil into the engine harness. This is a long shot but I would unplug the O2 sensor connector and just make sure the connector is clean and has no oil in it.

[jcramey16]

Did you ever figure out where the oil was coming from? Thanks.

[Mah1up]

Originally Posted by ArenGh

It's not the Valve Cover Gasket. I just replaced it and have done a thorough inspection around the motor with a mirror. It's all clean. I've also watched with a mirror with the motor running to make sure no oil is dripping onto the downpipe or o2 sensor.

Oil is bubbling at the o2 sensor. Any ideas what the problem could be?
The car is a stock X3 35ix with 72k miles.

Thanks!

Did you ever figure this out? I have the same problem, and tried tightening the o2 sensor but it still happens and is getting worse. I would like to know what it was as it sounds like I will be having to do whatever you did to fix it. Please let me know