Exhaust Manifold Studs - Service Precautions

91bmw04

Group 11 Engine


Bulletin Number 11 02 91 (3219)


Woodcliff Lake, NJ March 1991 Service Engineering


SUBJECT: Exhaust Manifold Studs

MODEL: E32/E34 (with M30 Engines)

Situation: The studs which are used to fasten the exhaust manifold to the exhaust pipe /catalyst may sheer off or the threads may be damaged when the selflocking nuts are loosened during a repair.

This damage is caused by the self-locking nut seizing on the stud thread.

Remedy: In order to avoid damage to the exhaust manifold studs during repairs and before any attempt is made to loosen the self-locking nuts, a few drops of engine oil should be applied to the exposed threaded section of the studs. This will prevent excessive torque being used when the nuts are loosened.

This method should be used on all stud/bolt and nut connections which are subjected to extreme temperature changes.

Note:

When reinstalling new self-locking nuts, always torque to the proper specifications as outlined in the Tightening Torque Values.

Only apply oil if you intend to loosen the nut; otherwise it will carbonize and form deposits in the stud threads making the nut even harder to remove.

Warranty
Status: Information only.