This is fairly simple. Here is a link to a webgallery of all the photos:
http://picasaweb.google.com/bfcOldSkool/SeatBeltRemoval

The rear seats are easiest. If you follow the rear seat removal in my sig, simply remove the seat bottom to access the bolts. There are two bolts in the middle for the straps that go to the seat backs and the middle belt strap. There are two other bolts on the outsides that mount the seat belt receiver or buckle for the shoulder straps.

As you can see they use a 16mm socket.

The front seat belt removal is based on a coupe, and may differ on a sedan.

There are two plastic parts you have to remove from the metal bar that holds the bottom of the seatbelt.

The cap on the left covers the front bolt.

The two halves of the donut-looking plastic trim piece on the right snap together around the metal bar and cover the hole in vertical carpet piece below the rear seats.

Here is the front bolt exposed after the plastic cap is removed.

The metal prongs are there to keep tension on the plastic cap. Be careful when removing the cap so that you don't bend these metal prongs.

Here is the hole in the back carpet that the bar goes through. As you can see the two plastic pieces have been removed.

The front bolt is removed with a T50 torx.

Here it is removed and you can see the aluminum cylindrical spacer. At this point you can slide the bottom of the seat belt off of the bar.

To remove the bar, you will need to rotate it towards the center of the car and pull it out of the body behind the back carpet.
In this picture the carpet is pulled back to reveal the hole in the body. Take note of the orientation of the bar and any special markings so that you can reinstall it correctly.

Here are the pieces after they are removed.

You can see the indentation and bump on the right side of the bar before the 90 degree bend. If you look at the picture above, you can see this as well. This part of the bar is what helps lock the two plastic cover pieces in place so they do not slide down the length of the bar.

Also the flat flange on the left side of the bar has an orientation as well when installed and you can see that from pictures above.

In order to access the actual seatbelts, you will need to remove the rear side panels. This procedure can be found in my headliner removal DIY:
http://forums.bimmerforums.com/forum/showpost.php?p=4081228&postcount=10
http://forums.bimmerforums.com/forum/showpost.php?p=4081233&postcount=11
http://forums.bimmerforums.com/forum/showpost.php?p=4081239&postcount=12

The bottom bolt requires a 16mm socket.

Good to know.
Thanks!!!

Next you need to remove the top nut.
This is detailed in the vent window DIY:
http://forums.bimmerforums.com/forum/showpost.php?p=3825902&postcount=2
http://forums.bimmerforums.com/forum/showpost.php?p=3825904&postcount=3

The first shows it with the cap on and the second shows it with the cap off, exposing the nut.

This nut requires a 16mm socket.

Do not overtighten this when you reinstall. It will not allow the top of the seatbelt to rotate when you pull the belt forward.

Here it is with the bolt removed.

Now we need to remove the metal bar below the b-pillar cover.

This requires the use of an 8mm socket.

Here it is with the entire assembly removed.

I have removed the entire b-pillar cover and vent windows and seals. You do not need to do this.

Here are the seat belt assemblies after removal.

Because of the poka-yoke of the little tab at the bottom, you can always be sure you install them on the correct side of the car. In the pictures above you can see this tab fits into a hole in the body.

They currently happen to be for sale in the link in my sig. ;)

great write up. I just swapped in another passanger side seat belt last night on my e36 coupe. it's very straight forward, even for the novice wrench turner.

snap, nice write up. This should be up in the FAQ section! I just have a question.

Will I need to buy a new Rear seat belt assembly if mine is fully retracted and in the locked position? I can't seem to release it to fix this tedious problem. I don't want to buy a new assembly if there is another way to release the tension.

Other than that, Thanks for the write up:buttrock

I think the seat belts built into the rear seatbacks lock when they are removed. I know it sounds weird, but I think that you have to lock the backs into place upright before you can release the tension on the belts....

Here is the front bolt exposed after the plastic cap is removed.

The metal prongs are there to keep tension on the plastic cap. Be careful when removing the cap so that you don't bend these metal prongs.

Does anyone know where to buy the ring with the metal prongs, or what the part number is? My dealer is baffled as to what it is, and has never seen it before. It doesn't show up on their parts list.

The ring with metal prongs is used to keep the plastic cap in place. It should come with the plastic cap.

why are u taking them out??? track car?

Have you ever removed, and replaced the deck cover? OMG what a bitch to put back in!

Does removing the seat belts affect the air bag light?

Have you ever removed, and replaced the deck cover? OMG what a bitch to put back in!

Yes. I have a DIY somewhere in the interior removal DIY articles I wrote. Probably in conjunction with headliner removal.

The ring with metal prongs is used to keep the plastic cap in place. It should come with the plastic cap.

Yeah, I explained what it's for, but it's not in their parts list, and it doesn't come with the caps.

Yeah, I explained what it's for, but it's not in their parts list, and it doesn't come with the caps.

Have them pull this item and look at it:
72118132627


http://realoem.com/bmw/showparts.do?model=BG13&mospid=47485&btnr=72_0201&hg=72&fg=05

Have them pull this item and look at it:
72118132627





Yup, I ordered 2 of them, and it's just the cap, no ring.

I have this for sale in my sig:
http://oldskool.zoto.com/img/45/6269534bb6fa277395876208b6caccc2-.jpg

but I have to check to see if I have the part you are looking for. It is highly likely that I do, but I don't see it in the pic.

Yeah, if you could check it, that would be great! I don't see it in the picture either, but keeping my fingers crossed.

Thanks!