Check Your Serpentine Belt (SIB 11 09 08 - Power Steering Pulley and Subframe)

[euro92]

Did some reading on the power steering pulley making contact with the subframe issue and wanted to share my findings.

What happens? Worst case scenario, engine failure via a series of events involving a damaged power steering pulley, shredded serpentine belt, crank seal, and valves.

How does it happen? Hit a bump hard enough and the inner (closest to the engine) edge of the power steering pulley might come into contact with the subframe.

What does BMW say? SIB 11 09 08
E82, E88 (1 Series) with N54 engine up to 4/08
E90, E92, E93 (3 Series) with N54 engine up to 4/08 except xi models

“If the axle carrier has any sign of contact, then the carrier must be replaced. For E90, E92, and E93 vehicles produced up to 3/19/07 which require replacement of the front axle carrier, the left side engine support (P/N 22 11 6 760 317) must also be installed.”

Front axle support 31116785639 (#1) - I believe this is a revised part
Engine supporting bracket, left 22116760317 (#1) - Note this is the bracket, not the rubber mount.

What else can be done? I'm not sure if there are any real solutions outside of what is advised in the SIB. However, there are some theories...

335is Engine Mounts
The 335is may have stiffer engine mounts which could limit vertical engine travel more so than regular 335i mounts. My only issue with this is the left 335is engine mount (same side as the power steering pulley) shares the same part number with the 335i (#2 & #2).

Shave/notch your subframe
This is a relatively rare issue which may be due to a slight miscalculation of clearances/tolerances on BMW’s part. That may explain why some may only have "skid" marks on their subframe while others end up with a damaged pulley and belt ([email protected] & [email protected]). With that said, perhaps removing a couple millimeters of material from the contact point on the subframe will buy us enough clearance to remedy the issue.

Here’s a video of my 50,000 mile (09/06) E92 335i showing contact marks on the subframe. Fortunately, my belt and pulley are still in good condition (for now), but I still plan on modifying the subframe when it comes time to replace the belt.



This next video shows my power steering pulley hasn't gone out of round.


Belt is still fine.


Removing air intake snorkel for a better view of the serpentine belt.


TLDR: Check your serpentine belt.