Rajaie has a great write-up over at Beisan Systems on changing out e39 thrust arm bushings with the arms still installed on the car. I'm posting my experience here (long) in case anyone else might be thinking of trying
Rajaie's approach.
Conventional wisdom is that you need to remove the thrust arms and replace the bushings with a shop press. If you are pulling the arms, though, you probably should be prepared to replace them outright as removal can damage the ball joints. I decided to give the "bushings only" Beisan procedure a shot for several reasons.
- I'd just replaced my struts a couple weeks back and didn't want to lift them out of the hub to pop the arm ball joints.
- I know the arms are at end-of-life but their ball joints are still good.
- I'm cheap. Perhaps the cheapest e39 owner, ever....
I installed a pair of Rein aftermarket bushings made in China. They seem identical in build to the Boges I pressed out. I may end up replacing the entire thrust arms within a year or two anyway but that depends on how well these Reins hold up.
The Beisan procedure calls for a 5-ton 3-jaw gear puller, a special pipe cap, and a press sleeve. I already had the puller. Since I have an i6 car, I bought the 1.5" socket weld cap recommended in the procedure from a local industrial plumbing supplier for $7, and tried to order the press sleeve tool through my local BMW dealer. [Note: the procedure calls for different-sized or psi-rated caps & BMW sleeve tools for the i6 and v8 cars....]
However, my local dealer refuses to order any "tools" so, before placing an order online, I investigated the O.D. specs for s
ocket weld couplings and found that certain 1.5" couplings (full or half) in the 3000 psi category have an O.D. of 57.25 mm -- about .75 mm less than the BMW press sleeve but still wide enough to match up well with the outer steel shells of the bushings. My local plumbing supply had one 3000-psi "full" coupling in stock, for $5. A "half" coupling might be preferable (they're shorter) if your puller is on the small side. If you visit a plumbing supply to get socket weld fittings, take your calipers....
I followed the Beisan procedure pretty much as written. (Aside: Rajaie mentions a hidden, hard-to-reach screw that's holding the front of the air duct on the driver's side. I accessed it from the front of the car bumper, pulling off the small grille piece, loosening the brake duct and getting a socket on it in plain sight.)
All the pre- and post-press steps of this procedure take far more time (hours) than the actual press work, which will be over in only minutes if all goes well. Pressing these bushings in and out of the arms with the tools described was a piece of cake even though I had to do it on my back (of course, with the car on jackstands). I'd say the only thing "hard" about it is getting the sleeve, cap, and puller all lined up and sorted on the thrust arm, but even that is nothing to fuss about.
I've been out and about with the car, have not yet gotten an alignment, but have driven on the expressway at 85 mph and have no vibrations or shimmies (my car didn't have any beforehand). At that speed, the car feels really settled, as if it were going much slower .... Now I know why these cars need an autobahn.
Some Observations
Whether you are replacing the arms entirely or just doing the bushings, you still have all that pre- and post-install work involved.... For the actual bushing press work, using the Beisan approach, after I had the control arm unbolted (bushing end) and lashed to its adjacent tie-rod with thick twine, I spent approx. 10 minutes total per side pressing the old bushing out and the new one in. The time factor here really boils down to how smoothly you are able to line up and center or square all the pieces (puller, cap, sleeve) against the thrust arm. When pressing the new bushing in, I made sure the puller jaws grabbing the other side of the thrust arm would not interfere with the leading edge of the bushing as it came through and exited the bore.
The rubber chambers in the old original (1999) Boges I took out were cracked in several *inside* and outside spots and had leaked out all their fluid (only dried residue inside). I didn't notice the inner cracks until I cut one bushing in half (cross-sectional) with a hacksaw to see how they're constructed. The outer shells are stainless steel and the square inner core the bolt passes through is aluminum.