E24: Overhaul rear trailing arms (rubber bushings no-DIY!)
This post describes the overhaul of the rear trailing arms on an E24 M635CSi, item 8 in the picture below. This includes replacement of the rubber bushings (item 9) that attach the trailing arms to the axle carrier frame. Unfortunately, pressing the bushings out of- and into the trailing arm requires some special heavy-duty tools, and eventually I had to fall back to the BMW workshop to get that job done. Nevertheless, the procedure requires to remove the trailing arms, so that is what is described in this post.
Pressing the rubber mounts out of (and back in to) the trailing arm, is virtually impossible with common pulling devices (usually consisting of a threaded spindle and press pieces). Maybe if you heat up the trailing arm.
BMW Repair Manual refers to the use of a hydraulic press, special tool 23 0 080, as shown in the picture below. Rather than the standard workshop press, this is a kind of hydraulic jack, with a counterstay attached to it. If you're handy with a welder, I guess you can assemble such tool from a standard 20T lift jack and parts of a sturdy puller...
The pictures may not always show the correct order in which different parts are disassembled. This is due to the fact that I overhauled the brake calipers, output shafts and various rubber mounts in one go, as can be read in my other posts.
1) LIFT CAR, REMOVE WHEELS, REMOVE BRAKE CALIPERS
A detailed procedure to remove the rear brake calipers can be found in my other post:
Overhaul rear brake calipers
That post also describes how to remove the handbrakes, and disconnect the handbrake cable and ABS sensor. Remove the handbrake Bowden cable and ABS sensor wiring from the clips on the trailing arm.
NOTE:
In my case the rear left ABS sensor came out smoothly, but the rear right sensor could not be removed without completely damaging it. The other post also describes the renewal of the ABS sensor.
2) REMOVE OUTPUT SHAFTS
You may want to loosen the 22mm bolt that connects the shock to the trailing arm while the output shaft is still in place.
A detailed procedure to remove the output shafts can be found in my other post:
Overhaul output shafts & C-V joints
3) REMOVE DOGBONES
Dogbones or Pitman arms connect the trailing arm to the axle carrier frame.
You may want to note the placement of the washers, there are two:
- one is located between the pitman arm and the trailing arm
- one is located between the nut and the axle carrier (subframe)
Also note the position of the dogbone itself, since it is not fully symmetrical. The metal between the two eyes of the dogbone is flat on one side (in my case the upside) and a kind of arch on the other side (in my case facing downward). Some specialists say it doesn't matter, but I installed it in the same way as it was before.
Remove the two 22mm bolts.
4) REMOVE TRAILING ARM
Before removing the trailing arm, disconnect the brake line. To avoid damaging the flare nut, you'll need a special half-open 11mm wrench and an open 14mm wrench as counter hold. Also unbolt the link that connects the trailing arm to the stabilizer bar with a 13mm socket.
Unbolt the two 19mm bolts that fix the trailing arm to the axle carrier, but leave the bolts in place for now. Support the trailing arm with a jack stand. Remove the 22mm bolt that fixes the strut to the trailing arm. Finally remove the bolts from the trailing arm, carefully lowering it.
5) OVERHAUL TRAILING ARM
Depending on the state of your trailing arm, you may just sand it a little and put a fresh layer of paint e.g. Hammerite onto it. In my case the arm was fully covered in dust and grease, so I decided to first clean it and have it sandblasted. After that, the bare metal is quite sensitive to corrosion so I immediately painted it with POR15 (even before I had the rubber bushings replaced, but that's a matter of planning).
WARNING:
I don't know what stuff is all in this POR15, but be aware that any stains on your hands will be there for two weeks and have to wear off. Once dried, there is no means to make it soluble again!
As said before, I had to visit the BMW workshop to have the old rubber bushings pressed out and new bushings pressed into the trailing arm. The bushings are 44 mm in diameter, you may have a go at it yourself for example with common pulling tools consisting of a spindle, a 45 mm tube and a 43 mm pressing plate but my bushings were stuck so hard that the spindle would be malformed.
Pressing the rubber mounts out of (and back in to) the trailing arm, is virtually impossible with common pulling devices (usually consisting of a threaded spindle and press pieces). Maybe if you heat up the trailing arm.
BMW Repair Manual refers to the use of a hydraulic press, special tool 23 0 080, as shown in the picture below. Rather than the standard workshop press, this is a kind of hydraulic jack, with a counterstay attached to it. If you're handy with a welder, I guess you can assemble such tool from a standard 20T lift jack and parts of a sturdy puller...
The pictures may not always show the correct order in which different parts are disassembled. This is due to the fact that I overhauled the brake calipers, output shafts and various rubber mounts in one go, as can be read in my other posts.
1) LIFT CAR, REMOVE WHEELS, REMOVE BRAKE CALIPERS
A detailed procedure to remove the rear brake calipers can be found in my other post:
Overhaul rear brake calipers
That post also describes how to remove the handbrakes, and disconnect the handbrake cable and ABS sensor. Remove the handbrake Bowden cable and ABS sensor wiring from the clips on the trailing arm.
NOTE:
In my case the rear left ABS sensor came out smoothly, but the rear right sensor could not be removed without completely damaging it. The other post also describes the renewal of the ABS sensor.
2) REMOVE OUTPUT SHAFTS
You may want to loosen the 22mm bolt that connects the shock to the trailing arm while the output shaft is still in place.
A detailed procedure to remove the output shafts can be found in my other post:
Overhaul output shafts & C-V joints
3) REMOVE DOGBONES
Dogbones or Pitman arms connect the trailing arm to the axle carrier frame.
You may want to note the placement of the washers, there are two:
- one is located between the pitman arm and the trailing arm
- one is located between the nut and the axle carrier (subframe)
Also note the position of the dogbone itself, since it is not fully symmetrical. The metal between the two eyes of the dogbone is flat on one side (in my case the upside) and a kind of arch on the other side (in my case facing downward). Some specialists say it doesn't matter, but I installed it in the same way as it was before.
Remove the two 22mm bolts.
4) REMOVE TRAILING ARM
Before removing the trailing arm, disconnect the brake line. To avoid damaging the flare nut, you'll need a special half-open 11mm wrench and an open 14mm wrench as counter hold. Also unbolt the link that connects the trailing arm to the stabilizer bar with a 13mm socket.
5) OVERHAUL TRAILING ARM
Depending on the state of your trailing arm, you may just sand it a little and put a fresh layer of paint e.g. Hammerite onto it. In my case the arm was fully covered in dust and grease, so I decided to first clean it and have it sandblasted. After that, the bare metal is quite sensitive to corrosion so I immediately painted it with POR15 (even before I had the rubber bushings replaced, but that's a matter of planning).
WARNING:
I don't know what stuff is all in this POR15, but be aware that any stains on your hands will be there for two weeks and have to wear off. Once dried, there is no means to make it soluble again!
As said before, I had to visit the BMW workshop to have the old rubber bushings pressed out and new bushings pressed into the trailing arm. The bushings are 44 mm in diameter, you may have a go at it yourself for example with common pulling tools consisting of a spindle, a 45 mm tube and a 43 mm pressing plate but my bushings were stuck so hard that the spindle would be malformed.
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