BMW 3 Series Blue Smoke On Cold Start — Valve Seals
Blue smoke from BMW 3 Series exhaust on cold startup that clears after 30-60 seconds indicates valve stem seal wear. Overnight the oil drains past the seals onto hot valve heads. The seal replacement can be done with the engine in the car using a special compression tool. Cost: £600-1,000. Catalytic converter damage follows if left untreated.
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