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P38 Diesel Separator/Breather


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So,... I am back from the UK, new downpipe & cat is fitted, Gott's charged me a bit less in the end which was a pleasant surprise.

Now i want to investigate the white 'smoke' from inside  the rocker cover, first call is check and clean the crankcase breather, but with the help of the parts lad in Gott's I established that my late model doesn't have the expected external breather/cyclone fitting under the top cover???? so does it have an internal filter like some of the 2 litre and 3 litre??? The parts book nor the Gott parts computer software was any help,... anyone been there and done it please??

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As far as I know the later version of the BMW doesn't use a separator, but only a breather hose. No filters or such. Not a bad decision, as the separators are know to clog and usually leak where they connect to the airpipe. Only downside would be if the engine has too much pressure in the crank case, as it allows more oil into the intake so a higher risk of the engine running on oil and out of control.

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  • 2 months later...

Just looking at the date here, I guess its been a while!,... there have been distractions....

Anyway set to yesterday and lifted the bonnet,...


At this point I wondered whether to read the manual or just start, I wasn't feeling very brave, confidence isn't high at the moment, but in the end I just got on with it.

A few minutes later, very straightforward to undo and we can see inside.....IMG_20190829_163813.thumb.jpg.50609b4ca51234cba1ef341117b3a2c5.jpg

18 years of muck 👀 , doesn't look as if it has ever been off before.


Undoing the inner lining reveals the nature of the beast,... breather port has a control valve inside and a huge wire filter,...

3 or 4 litres of petrol later and things seems a bit brighter....


I have cleaned out the diaphragm valve thingy as best I can, I had a scratch around to see if replacements were available but there isn't much out there.


Lets hope a good flush through is sufficient, I am just going out this morning to slot it all back together and see it it helps the white smoke situation.


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Just to be sure, you do have the plastic intake duct that goes across the engine block from the filter to the turbor? There should be a short hose from th valve cover to this intake.

Where is the smoke coming from? Exhaust or under bonnet?


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Thanks for looking at this Filip

Smoke is visible when you remove the oil filler cap from the rocker cover (yellow one).

Yes I have the small pipe in place. 

Have just been doing a compression test,

No.1, 325 psi

No.2, 320 psi

No.3, 365 psi

No.4, 340 psi

No.5, 360 psi

No.6, 285 psi

So I wonder if I have a broken ring on No.6??



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I agree, n° 6 is a bit low. But unless you're having driveability issues or overheating, I'd leave it alone. Not the easiest engine to work on, and with the filler cap installed the crank ventilaton will take care of any smoke. Maybe do an oil change if you haven't done so recently.


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Thanks, you have re-inforced my own feelings,... oil was fresh in May, done about 4500 miles, I'll change it again before the winter, otherwise it is driving fine at the moment, apart from trying to eliminate EAS leaks.

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The best laid plans and all that.........

Turned the house upside down looking for the intake manifold gaskets I ordered and failed!

There will now be a delay while I order some more (old ones are perished), .... so I decided to take down the sump and check the gunk levels internally and check for debris. 

Not too bad as it happens, hardly any gritty bits and no sludge to speak of, could be worse. 

Must get a proper parts washer, very messy cleaning that lot up without 💥💦

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  • 3 weeks later...

Postscript to this is that the new gaskets took sooo long to turn up (note to self, that's the second time Craddocks have been desperately slow) that I had stumbled across the originals. So all back together and wouldn't start.... been a bit Mildly miffed off with it but after going back over everything I had done, I started looking elsewhere and found a large 80A fuse in the ECM box had blown, not sure what I have done that could have caused that, I had been working with the battery connected but didn't as far as I know short anything I shouldn't have.

Anyway, I have no replacement to hand so for the present it starts and runs with a stripped down boxy fuse from a D2 fuse box, its only 50A but seems to work for the present, off to look for 80A fuses.

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