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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > M47N2 Oil Leak - Crankcase Breather Wet?



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      04-02-2017, 08:11 AM   #1
Digitalize
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M47N2 Oil Leak - Crankcase Breather Wet?

Looking for a bit of advice here and if anyone's had the same or similar before.

Basically found oil on my drive, started to get worried that I'd cracked my sump but it seems worse than that.

Oil has run down the exhaust from the big box after the turbo but also down the back of the engine block and gearbox. I pulled the air filter out and there's a small amount of oil on it that looks like it's been sucked from a small hole in the bottom near the back. Removing the crankcase breather it was very wet with oil and looked like it had a pool of oil in a crevice near it, and the back was oily but not necessarily wet like I'd imagine my source is.

Unfortunately I can't seem to get a good angle to see if there's oil on the turbo itself or any real source of the leak, just what it's leaking on.

I've had my crankcase breather changed before, maybe 40k ago, but I'm not sure how oily it should be? I know it separates oil so it must be at least slightly oily? But I'm thinking of changing this.

Unsure if it's related but my MPG also seems to have dropped a little bit.

If the crankcase pressure builds up would it cause an oil leak through the breather seals?

I was dreading a crack in the sump but I sort of wish it had been now!

There's a small amount of oil in the EGR but no more than I suppose is considered 'normal'.

The car is 213k so I'm guessing it's not beyond possibility of a seal of gasket leaking, just trying to work out where!

I had glowplugs changed and swirlflaps blanked probably a month ago, no idea if anything could have been disturbed during then. The airfilter was done after that and there was no oil on the old one like there is the new one.

I'll add some photos later this evening to try and show things a bit better.
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      04-05-2017, 07:43 AM   #2
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Bit of a bump/update, no photos as I can't really see anything still.

It's definitely dripping on to the cat after the turbo, and its oily on the underside of the cylinder head cover. Wondering if it could be a leak from the gasket around there? Is there anything else near there that could leak and is more common? Only other sort of idea is the oil line for the turbo but I can't see it at all.
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      04-05-2017, 08:37 AM   #3
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Top cover gasket? Oil filter gasket? Oil cooler gasket?
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      04-05-2017, 09:54 AM   #4
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Quote:
Originally Posted by Digitalize View Post
Bit of a bump/update, no photos as I can't really see anything still.

It's definitely dripping on to the cat after the turbo, and its oily on the underside of the cylinder head cover. Wondering if it could be a leak from the gasket around there? Is there anything else near there that could leak and is more common? Only other sort of idea is the oil line for the turbo but I can't see it at all.
Maybe it's the cylinder head cover gasket? Turbo oil line goes in the front of engine, so this shouldn't be a problem as You have a leak on the back.
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      04-05-2017, 04:51 PM   #5
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I had oil all over my engine that had me in panic. When my mechanic told me to fit a new oil filler cap gasket I was sceptical but he was right. Apparently high pressure pushes oil through if the gasket is not very tight.
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      04-05-2017, 08:41 PM   #6
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My current best guess is Cylinder Head Cover Gasket, but it's just a guess. Gasket is 30 from BMW, so thinking I may as well spend a day pulling it off to get a better view of the engine below it, and check any gaskets and change the main one. The inlet was off recently like I said but it doesn't have oil flowing through it so I don't think that caused it.

It's dry around the oil filler from what I can tell.
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      04-06-2017, 07:59 AM   #7
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How much oil are you losing? Try cleaning it up and then throwing some talc onto the area to trace where the leak maybe from?
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      04-06-2017, 08:48 PM   #8
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At the moment I'm not entirely sure but I'm doing about 500 miles over the weekend and have picked up a 2L oil and removed my undertrays. Enough for it to drip on to the floor after 5-10 mins of being parked.

It's only when the engine is hot too, just moving it around/in out the garage doesn't seem to make it leak. Going to keep the RPMs down in case it's related to oil pressure etc.
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