1+,

* Once the belt is removed, and the whole area is exposed, the OFH gasket is a piece of cake. Read forums, but here are the cautions re OFH gasket:
a. Use only BMW part ($6)
b. Clean and remove all traces of old gasket.
c. I use a small amount of grease to help hold the new gasket in place.
d. Some people have stripped one of the 6 bolts (requiring Helicoil, Timesert etc.), so I think if you can reduce the torque by a few ft*lb, then apply a bit of Loctite, you will be fine.

* All M52, M52TU, M54 engines may come from factory with Bosch vs Valeo etc. etc. But Bosch AL0703N fits all of them.

And I6 is air-cooled, not water-cooled.
Better yet, remove that air duct feeding the alternator, it is nothing but trouble!

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT