BMW valve cover gasket leak — symptoms, cost, and DIY replacement guide

Done this job dozens of times. Most important tip: photograph the bolt pattern before removal. The N54/N55 valve cover uses 3 different bolt lengths — putting a long bolt in a short hole can crack the head. Also replace the eccentric shaft sensor seal (N52) or VANOS solenoid O-rings (N54/N55) while the cover is off. For the N20, BMW released an updated valve cover (11 12 8 645 888) that fixes the chronic leaking — about 180 EUR but solves it permanently.

Just did this on my E90 325i N52 as my first major DIY job. Took about 4 hours. Hardest part was cleaning old gasket residue — use a plastic scraper and brake cleaner, never metal on aluminum. Total cost 45 EUR vs 450 EUR shop quote. Also check the PCV valve while the cover is off — on the N52 it is integrated into the valve cover. If stuck open, it causes excessive oil consumption. New valve cover with PCV is about 150 EUR and solves both problems.