[icarossw]

Reads the manual [BMW 3 Series, Service Manual BentleyPublishers No: B310] for my E93 with N54 engine, that the servo pump is mounted with alu bolts.
And alu bolts need to be scrapped after use as they probably are stretched during assembly.

When remounting my servo pump, I decided to test the old bolts with a magnet which stuck to the bolts!!
A few well-chosen words flew through my head about service shops that skimp on original parts !!!
But then it struck me to test the new bolts supplied by BMW, now with the same result !!!!

So what is correct, should it be alu bolts or is the manuals wrong, (even BMW claimed it should be alu bolts) and what moment should be used for mounting the bolts (I guess if it is steel it doesn't matter as much, even if I don't want crush the threads in the aluminum block)

Anyone who knows?

[vtl]

Bentley publishers service manual is not the factory manual for these cars. It a service manual written by a third party.

If you want correct information, always use the service instructions that come from the BMW ISTA software.

A good web rip of BMW ISTA service instructions is located here:
https://newtis.info

By servo pump you mean the power steering pump? These are definitely steel on N54

[malgyver]

I guess BMW had some philosophy of why they chose the aluminum bolts, even though not all of them around the motor assembly are aluminum. This is to the ire of many enthusiasts here and elsewhere. But times, I guess, have changed. I still use the aluminum bolts they spec, such as bellhousing, oil pan, etc, because they are usually pretty cheap and as long as you do a little planning, you can get them to your doorstep pretty quickly.

[nissubaru]

Originally Posted by malgyver

I guess BMW had some philosophy of why they chose the aluminum bolts, even though not all of them around the motor assembly are aluminum. This is to the ire of many enthusiasts here and elsewhere. But times, I guess, have changed. I still use the aluminum bolts they spec, such as bellhousing, oil pan, etc, because they are usually pretty cheap and as long as you do a little planning, you can get them to your doorstep pretty quickly.

My only gripe with the aluminum bellhousing bolts (minus being 1 time use) is the fact that they are stretch bolts which require angle as well as torque. The bellhousing bolts I did yesterday were 25nm initial torque, + 120 degrees + 20 degrees. Not the end of the world, but doing it on your back and getting 120 degrees of swing is a bitch.

The steel bolts are just regular ol torque and you can't really screw that up. However they were $36 for the 5 bolts when I checked with the dealer.