[marinmcgreevy]

Hi All,

My 07 335i has suddenly started burning oil. Prior, it would burn a quart every 3000mi. Suddenly the quart oil light would go on after about 600 mi. My car has 127kmi. The turbos were replaced at 40k. There is no visible oil smoke plume out the exhaust. The car runs as great as ever.

However, there is a distinctive smell of oil in the engine bay. No visible leaks or drips. Everything is dry. I have been running an ECS oil catch can for about 35kmi and my car has always had low blow by and the catch can has never accumulated much oil. The dip stick in the catch can now has a frothy whitish build up. Oh no. But, the radiator expansion tank is clean. No oil. Inside the engine, viewed from the oil filler hole is clean as it always is. But when the oil filler cap is open now there is a distinctive vapor coming out. This vapor does not have any coolant smell to it. Just oil.

Any clues to the source of the step change in oil consumption? Vapor coming out the oil filler? The froth on the catch can dip stick?


The increase in oil consumption makes me think turbo oil seals. The vapor makes me think head gasket. The photo of the oil filler with the vapor was taken after the car had been driven three hours at 70+ mph. The car does not run hot.

[Pladi]

Head gasket usually will have smoke.. that much oil has to go somewhere. Did u check from underneath for leaks ?

[marinmcgreevy]

No leaks that i can find.

[robthewrench]

The oil smell is oil burning on the exhaust. This is why you may not be seeing a significant quantity. It could be either the valve cover which then leaks on the exhaust or a part of the turbos. Since the valve cover is way cheaper, you should check this first.

[lowrydr310]

The froth could just be condensation mixing with the oil vapors in the PCV plumbing and accumulating in your catch can. I've personally never had the issue, but read several E90 owners complaining of the same froth under their oil caps.

I too have an oil consumption issue (~1qt per 2000 miles or so), slight oil smell under the hood after driving but NO visible leaks, NO smoke out the tailpipe, NO drips on the ground, etc. I haven't checked yet but I'm guessing there's an issue with the PCV system somewhere, whether it's a cracked hose or a check valve that isn't functioning correctly.

[robthewrench]

On your comment about not seeing any smoke out the exhaust: It can be very difficult to see oil smoke in the exhaust if you're consuming only a quart in ~500 miles. This is like driving at 60 miles per hour for 8 hours. More hours if lower speeds.

It might be easier to look for burned oil residue on the tailpipes or bumper, or do a compression test to try and find worn rings. Worn valve guides can also be a loss of oil into the combustion chamber.

[marinmcgreevy]

Well I replaced the valve cover gasket today. It was leaking at the back corner, just beyond the stainless steel “gutter” that prevents oil dripping directly on the turbos. I made a mistake in coating the gasket with grease. The new gasket was installed dry on dry and very clean seating surfaces.

The biggest find was the crankcase breather catch can system. I installed the ECS Tuning catch can when I replaced the valve cover and gasket. I was concerned that there never seemed to be any oil accumulated in the catch can. When I pulled it apart today the catch can was full of water and had oil froth. The vent hose from the valve cover to the catch can was completely plugged with oil/water froth. Check the photos. The engine was still very clean and the inside of the valve cover had no evidence of water.

Has anyone else seen the oil froth in their ECS catch can?

All cleaned up with a new gasket and the catch can sytem completely cleaned. Will see how the oil consumption lines out.

I am getting pretty efficient at replacing the valve cover gasket.