This is a hidden Achilles heel on the S54 engine and often goes mis-diagnosed - one of the bolts that holds a timing chain guide will un-screw itself and back out of the cylinder head. If it releases the timing chain guide, there's no limit to the damage it can cause... This bolt is located at the forward part of the cylinder head, behind the thermostat and oil filter housing. The first sign of trouble is oil leaking from this area as the screw backs out and oil leaks past its aluminum seal washer. This is often mis-diagnosed as a common failure of the S54 oil filter housing gasket
. While that is a possibility, don't delay the service and have the housing gasket and this seal replaced! The other telltale sign of trouble is a rattle from the top or intake side of the engine. This is either the chain guide rattling or the chain itself and is often mistaken for VANOS rattle. The bolt itself does not need replacing but we're advertising one with the washer seal. The seal is also available separately. Add a bit of Loctite to the bolt screws when you put it back in.
BMW Fitments:3 Series
E46 (01-06) > M3Z Series
Z3 (01-02) > M Coupe
Z3 (01-02) > M RoadsterZ Series
E85 (06-08) > Z4 M Roadster
E86 (06-08) > Z4 M Coupe