after lots of work STILL got vacuum leak and oil leaks

[Cylow]

okay. I 've changed pretty much every vacuum hose and grommet on my x3 M54 engine now.
Pipes were typically failing and cracking from age.
thus idling was rough due to vacuum leaks and oil was getting out here and there and dripping - thanks to the slant engine, on the exhaust system, burning, causing smoke and coming into the cab through the vents.

So changed the valve cover gasket. valve cover rubber seals (all 15), ccv oil separator and ALL connective crank case breather and return to rocker cover pipes and o rings.
Changed oil filter and replaced gaskets.
Great. all good for about three days.
Then that oil leak again, smoke again where it runs down and burns on the exhaust and the classic M54 rough idle.
It's a very sensitive engine to ANY vacuum system failures.
So i'm kind of out of ideas now.
I'll get underneath ad try and find the source of the oil leak - where it's likely i'll find the vacuum leak.

I suspect its the valve cover gasket - which i replaced - the valve cover is plastic and is rumoured to not sandwhich the gasket tightly all around due to it waring - from being plastic.

Considering removing it and using RTV black auto silicon to try andf assure a better seal.

I haven't changed the spark plug seals yet - so may do that first. but i know that's not where the oil leak is.
any help appreciated.

[jclausen]

I would take an inspection mirror and flash light and look at the valve cover gasket, maybe it popped out a bit when the cover was installed. Spark plugs are easy to replace when doing the valve cover gasket. As far as vacuum leaks go I had a car the other day after repairing obvious vacuum leaks, we got another lean fault. Found the plastic jet valve leaking just a bit, its that black valve that has one hose going to the air boot elbow, another hose to the brake booster, and the other hose goes under the intake manifold

[my1stE30]

in all of that work ... did you check the oil filter housing gasket (and check for cracks in the oil filter housing )?

after all that, I would then turn to inspecting the valve cover gasket as suggested above

[MarkJWT]

Hi

Im having similar problems

I have changed:

MAF Sensor
All CCV system & hoses (brittle and full of holes)
Air intake boot (Full of holes)
Fuel cap
Fuel pump
Fuel injectors

I had a smoke test which has confirmed no vacuum leaks now

For the 'knocking sound' at low revs in traffic I replaced the budget sh!te tyres with Dunlop Sport SP01 tyres (cured the knocking!)

Cleared the adaptations and it was running perfect for a week or so, then the P0171 and P0174 codes returned (bank 1 & 2)

My Long Term Fuel Trims (LTFT) are high (>20%)

I also seem to have transmission fluid leaking from the front (I suspected the front diff, but can't pin point from where its coming from)

Starting to suspect O2 sensors. The post cat ones have a lot of 'sh!te' on them including a bit of oil. The pre cat ones look ok, but who knows? The sheath around one of the sensors looks damaged (possibly heat). When I hook my OBDC scan tool and look at the graph, three of the sensors produce a regular sine wave, the other one produces a flat line most of the time, then seemingly random fluctuations at other times, and at other times it will produce a long transition sine wave.

Starting to get bored of this cat and mouse game....

[vinyldude]

If it falls on the exhaust, it almost has to be valve cover gasket related - not really other possibilities. I second the suggestion to double check the valve cover installation. The gasket goes easily out-of-place in the half moons in the back. The slanted back corner may also easily leak. I would not go the RTV route myself. I would get another valve cover if everything else fails. You are correct - it is plastic and basically garbage.

I have had an oil leak on the other side (driver side). I did the oil pan gasket, and now recently replaced the oil filter housing gasket and CCV valve plus all the hoses. I think it was the oil filter housing gasket, but knocking on wood.

[Cylow]

Thanks for the input.
I'd say I'll remove the rocker cover and insect the new gasket cover.
Quite possibly the lobe is out of place.
In fact I added small amounts of rtv to the corners of the lobes in accordance with much advice . The head even had pre existing silicon there which I removed. But I fluffed it and had yo take it off then put it on again as I rebuilt the cover and left the upper cam oil cover out of the engine .. Doh !!
Also I had changed the oil filter and oil filter gasket.

[MarkJWT]

I found mine!

The MAF I installed was substandard (£38!) I put my old one back in and it's driving like it should - no lean codes in a week.

Check your MAF!

[blumpie]

For me, the final fix was the oil separator valve. Get the whole kit with all the hoses (if you have not replaced them already.