Trailing Arm Bushings
I give credit to Marco Romani for the initial publishing of these instructions and much of what I've printed below is taken verbatim from his initial post in March 1999. I have used these instructions myself and found them to be very thorough and accurate. However, I have added a few notes and changes in red type based on my own experience.
First off, I suggest doing this procedure in five steps:
1) Read all the instructions thoroughly before you do anything else.
2) Order new trailing arm bushings and have them in your possession before you start. (I suggest ordering the bushings from a 96+ M3 as they are made of harder rubber and will last longer/perform better.)
3) Jack up your car and drop the tailing arm, remove the "console", and examine how the entire procedure will go.
4) Go to the hardware store and buy everything else you'll need.
5) Begin the work on one side of the car. Do not start the other side until you've completed the first side as you may decide to change your methodology. I completed the first side in around 4 hours, but shortened it to under two hours on the second side.
Lastly, don't try this if you need to use your car immediately afterward unless you are extremely confident in your abilities. Because once you drill out your first bushing, you are committed to finishing the job or hauling your car to a mechanic on a flatbed. Having a second car available during the process may prove to be invaluable.
OK, let's get it on...
- 5hp air compressor with Air Hammer and various chisels. (air hammer not needed with BT's hacksaw method)
- An oil filter wrench (not the chain or strap kind, but the kind that fits over the top of the oil filter on most non-BMW cars, and that you use a wrench to tighten or loosen the oil filter). I think it was 65mm in diameter, it needs to be bigger than the ID of the bushing housing in the trailing arm. A semi-truck tire lug nut socket would also work, but they are 4 times more expensive.
- A bunch of 8" long 3/8" bolts (or threaded rod) from Home Depot w/ a bunch of nuts.
- A bunch of 3/8" through 1/2" id washers from HD. The OD of the biggest washers will need to be as large as the flange on the bushing and relatively thick for a washer. (take the bushing with you to HD)
- A 8" 2 armed gear puller (that will be used as a bushing pusher) (I don't recall needing this)
- A 3" square 1/4" thick piece of scrap metal (aluminum or steel is fine).
- a drill with the biggest diameter bit you can find.
- plus Various 1/2 sockets, torque wrench (that goes to at least 70ft lbs), wrenches, jack stands, jack, blah, blah, blah.
R&R of Trailing Arm Bushing Instructions
(WEAR SAFETY GLASSES!!!!!!!!!)
1) Jack up the rear of the car and support on jack stands. Remove the rear wheel.
2) Disconnect the brake line where it connects to the trailing arm. (this needed to be done since the trailing arm when it is unbolted from the car will end up stretching the brake line). Put a piece of Saran-wrap over the brake fluid reservoir opening and screw the brake fluid cap back on. This will slow the leaking of the brake fluid from the disconnected brake line. I couldn't find anything to plug the line and I didn't want to "clamp" it closed since it was a stainless steel brake line. (I didn't need to disconnect my brakes lines when I did the job, so don't do it unless you have to.)
3) Unbolt the trailing arm from the car. There are 3 18mm bolts holding it on the car. I marked the flange plate ("Console " in BMW speak) and car body with a grease pencil so that when I re-attached the trailing arm to the car my alignment wouldn't be too badly screwed up. (Be as precise as you can here. If you're careful you shouldn't need a rear alignment when you're done.) Put a jack under the trailing arm so that when you loosen the last bolt it doesn't just drop down (and smack you in the head). The bolts are to be torqued to 54 ft lbs, but seemed a lot tighter than that, so use an impact wrench if you have one to loosen them.
4) The trailing arm is attached to the "console" by a bolt and nut that goes through the bushing. It is torqued to 70 ft lbs and since you're working in pretty cramped quarters you'll need the impact wrench again to remove the bolt and nut. The console should just lift off exposing the bushing.
5) Measure the distance between the flange on the old bushing and the trailing arm. My left one was 2mm and the right was 1.5mm. You'll want to install the new bushing to the same distance. I don't know why but that is what the BMW micro fiche said to do. Remember the way the bushing is oriented in the trailing arm. You want the new one to look the same way.
(Read steps 6 and 7 then skip to my "Replacement Instructions" for these steps below.)
6) Now comes the hard part. The trailing arm bushing is a bushing made from rubber and "cheap white metal". It's kind of a Ho-Ho looking thing. The Ho-Ho filling is a white metal cylinder where the bolt that holds the console in place goes. The cake part of the Ho-Ho (bushing) is some sort of rubber substance. The frosting/shell of the Ho-Ho bushing is more white metal, with a flange on one end facing to the outside of the car. Here's an attempt at ASCII art of what bushing looks like looking at it straight on. ( o ) The ( ) are the flange, the o is the white metal cylinder, the space between the () and the o is the rubber. You need to remove this beast from its liar in the trailing arm. This is where the drill comes in. (you better be committed to going the distance because from here on in the only way the car is going anywhere is via a flat bed!) Take the drill and start drilling holes in the rubber around the perimeter or the white metal cylinder until you've drilled all around it. Then cut the damn thing out. Now you have a mangled bushing that is still firmly in place.
7) Now the fun part. (Tim Allen would be proud). Take the air hammer and a thin chisel and beat the crap out of the white metal flange (working from the inside part of the car to the outside) until the flange snaps off. You can now see where the outer metal part of the bushing is set into the trailing arm. Next take the air hammer and a tapered cylindrical chisel and carefully (careful and air hammer don't seem to go together) start bending the outer part of the white metal of the bushing into the space you created by drilling out the inner white metal cylinder. Once you've made some nice bends in the beast, change air hammer bit from the tapered cylinder to a cutting bit. The bit looks kind of like this ====< Where the < is the cutting edge. Use this bit on the white metal you mangled with the tapered bit. Eventually the bushing will collapse in on itself and start pushing out the backside of the trailing arm. When you see this happen start using the air hammer on the white metal that is now exposed on the backside of the trailing arm and it will push out the front of the trailing arm. THERE WAS MUCH REJOICING!!!! Yeah, Yeah! (my apologies to Monty Python).
BT'S REPLACEMENT INSTRUCTIONS
FOR STEPS 6 & 7....
The bushing consists of three parts: aluminum outer, rubber middle, and steel center. (Marco's "Ho-Ho lookin' thing" description above is not only accurate, but wonderful. <g>) You want to remove the whole thing from the trailing arm. Take your drill and make a hole through the rubber portion next to the aluminum sleeve (outer edge) large enough to slide a hacksaw (or Sawzall) blade through. Then cut a slit in the outer aluminum sleeve to reduce the pressure on the press-in fit and the whole bushing will slide right out of the arm. If it doesn't slide out easily, drill a couple more holes through the rubber to allow the aluminum sleeve to compress more. Be careful to not cut into the trailing arm itself, but don't worry if you nick it a bit. Just clean up any burrs with sandpaper or a file so that the new bushing will slide in with minimal interference.
8) Now time for installation. Find the
bolts and nuts, washers, and oil filter wrench you bought. Take
the oil filter wrench and place it on the in-board side of the
trailing arm bushing hole. Run the bolt through it to
the other side of the trailing arm bushing hole. Slide the new bushing over the bolt and position it so that it will be in the same orientation as the old bushing once it is installed. Take the big washer and slide it over the bolt, then use the other washers to close up the ID of the bigger washer. Finally place a nut over the bolt and start tightening. If I explained this right the nut will force the smaller washers onto the big washer, the big washer will apply pressure to the bushing and the bushing will start sliding into the trailing arm housing. It may start a little crooked but it should then start to go in straight (at least mine did). Start tightening the bolt and nut until the bushing is about 3/4th of the way in or the bolt breaks, which ever comes first. They are cheap bolts ya know! Remove the bolt, washers, oil filter wrench etc. You now have a bushing which is about 3/4 of the way in.
9) Now take the gear puller and the metal plate. Place the metal plate over the bushing, and then position the gear puller arms around the bushing to the in-board side of the trailing arm bushing housing. ( a three armed gear puller will not work due to the geometry of the trailing arm) Start tightening the gear puller, the screw of the gear puller will put pressure on the plate, which in turn will force the bushing into its housing. As you get close remember to start measuring the distance between the bushing flange and the trailing arm. Stop when you get to the distance measured in #5.
(I never needed the gear puller. Something about the bolts and washers I bought, I guess.)
10) Re-assemble the console/bolt/trailing arm assembly (torque bolt to 70ft lbs).
11) Re-attach console to car body trying to get close to your marks. (You should be able to hit your marks precisely. If you made good marks in the first place, your rear alignment won't change.) (torque 3 bolts to 54ft lbs)
12) Re-attach brake line. (if needed)
13) Do steps 1-13 on other side of the car.
14) Bleed brakes. (if needed)
15) Get car aligned. (if needed)
16) Enjoy the $500 dollars you saved! (definitely!!)
Please send me an email with any notes, improvements, or suggestions to these instructions and I'll give you full credit.