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419 Posts
Discussion Starter · #1 ·
Ok so I've been dealing with random check engine codes... Generic OBD II code was the dreaded P0171 which is soooo vague. But the BMW specific codes, multiples had me guessing at what it might be...

Did an intake Smoke test originally and found a leak at the output side of the intercooler... Fixed it and the codes still returned...

So I decided to do a REVERSE smoke test by filling the valve cover side thru the oil filler cap... Let the pressure build for a long time.... And a hairline crack in the valve cover presented itself.... This was no big deal since I had replaced the valve cover roughly 40k ago.. and I used FCP euro so it's warrantied and will be free...

Well that's where the real fun starts.... I continued to fill the system with smoke(5-10 mins) and a rather large leak presented itself from the top of the front crank seal馃檮馃檮

So it's very apparent that I have a highly reduced amount of vacuum due to the leaks causing the car to over compensate by adding fuel and causing a bank 1 Lean error as well... I know another member here recently posted a mass air leak plausible thread as well.... Might I suggest you are probably dealing with similar leaks ... Reverse smoke test it...

So I've never done a crank seal repair and would love any input anyone can offer...

Hopefully my time spent trying to figure this out helps someone else not have to search down a very vague error code ...

Thanks guys - here's a video of the hairline crack.. and pics of the standing codes..

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1,479 Posts
Good info here. thanks. Just curious...what engine & miles?

2013 X5 E70 N55
498 Posts
I would be a bit suspicious of pressurizing the crankcase. It normally runs under a slight vacuum and will therefore normally be pulling in the lip seal on the crank. Pressurizing (with your smoke) will tend to push past this crank seal.

My 28A0 code was repaired with a new genuine valve cover assembly. A vacuum meter showed I had a paltry -20mmHg of vacuum in the crankcase when the spec is -31.5 to -43mmHg (below atmosphere.) Plugging the crankcase breather hose with my finger immediately pushed it up to -36mmHg suggesting the one-way valve inside the cover was leaking-by.
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