03-31-2013, 08:00 PM
Join Date: Mar 2012
Location: austin, tx
My Ride: 04 M3 Convertible
Found the problem!
OK, so I finally got fed up with this enough to pull the driver seat (the problem one). I unbolted all sorts of things until I found the problem. Here are pics of getting to the part that actually matters. You only need to worry about the driver side of this seat to get to where the problem is - although I ended up pulling the entire passenger side off too.
First, pull the seat, no pics of that, but there are 5 bolts - 2 in front and 3 in back. Tilt the seat and unplug the harness. Remove the seat.
Past here nearly all bolts are torx, so have your torx set handy. I think I used 3 different sizes.
Put the seat on its passenger (right) side and remove the power controls. There are clips from the bottom. When undone, the whole thing can be tilted up and then the controls can be unplugged and removed.
Unbolt the controls panel and remove it.
Remove the rear hinge cover now that the panel covering it is gone. There is a small torx on the back of it and it comes off.
This is what the side looks like with those things removed.
At this point I put the seat back up on it's rails and started moving it around to see what had the most slack. What I noticed was that the driver side wobbled a lot more than passenger side. I noticed it was the hinged that's spring loaded to balance the seat bottom.
To get a better look and necessary access, I unbolted the front brackets that attach the seat to all the mechanisms below.
This finally gave me enough access to pull the bolt and inspect the hinge. This side appears to have a bushing, where as the passenger side doesn't - not sure why.
To separate the hinge, I had to remove the spring that holds it from inside.
You can see it on the right still in place.
And removed and hinge separated.
Now here's the weird thing. They used a rubber bushing similar to a RTAB or diff mount just much smaller. It APPEARS to be eccentric, but to me that looks just to be how it wore out.
The sleeve on the inside was barely holding in and I was able to pull it out with my fingers.
I tried using a c-clamp and some sockets to try to press the rest of the bushing out but I couldn't get it to budge, so I took a hacksaw and cut the bushing in a couple of places and chipped it out.
Alright, so I figured out the problem - and I bet a lot of convertible bimmers have this (possibly coupes, too, if the setup is the same).
The issue is that I cannot for the life of me find the part to replace it with. RealOEM does not list any of this and I haven't gone to the stealership yet. I'm considering ordering a custom size delrin bushing kit or just making one out of a block of delrin myself.
The sizes are as follows:
Bushing OD 23mm. The housing is about 16mm long.
Sleeve OD 13mm. Sleeve is about 19mm long.
Sleeve ID is 10mm. This is easy since I can probably just reuse the sleeve after I clean it up.
Big question, does anyone know if this bushing can be sourced or know of a place where you can order bushings by the size?