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6 minute read
BMW e39 Control Arm Replacement
Compliments of fudman @ www.bimmerfest.com
A few weeks ago, I had posted on a front suspension problem that led to an inspection failure. I had several responses suggesting tie rods, thrust arm bushings and even bearings. Not wanting to spend a lot of time (it’s still winter here) & money replacing multiple suspension parts, I conducted a visual inspection of the problem area. I determined that the cause of the problem was a control arm ball joint based on noticeable play in the ball joint when twisting on the brake rotor. So I ordered left and right control arms and proceeded to replace them (after my vacation). Here is the play by play with some interesting lessons learned. BTW, I am no experienced mechanic so if I can do this, anyone can. Having the right tools makes all the difference.
The Bentley indicated a relatively straightforward control arm replacement process. Remove one bolt at the control arm bushing and remove the ball joint nut to replace the control arm. First off, all the nuts and bolts were weird sizes, 16mm, 18mm and 22mm. I have multiple wrench sets and none of them had a 16mm or 18mm wrench. Fortunately, my socket sets had these sizes. I borrowed a Harbor Freight ball joint tool from Chris (Neversaynever) and Dave (gtxragtop) stopped by to assist. My sincere thanx to both of them!
I jacked the front of the car up using the center jacking point, chocked the rear wheels and lowered the car onto jackstands. I then removed the wheels and proceeded to remove the control arms. The first hiccup was removing the level sensor attached to the passenger side control arm. The attaching mechanism is a spring clip that has no easy way to disengage (photo). I used a small chisel to finally get this spring clip to open. It took about 30 minutes of fiddling to avoid breaking it. A hose clamp would have been much easier.
I soaked the nuts with PB Blaster and they came off without a hitch. The bolt head on the bushing bolt is 16mm and the nut is 18mm. I used a socket wrench on the bolt head and an adjustable wrench to hold the nut side. The ball joint nut uses a 22mm socket for removal. Getting the ball joint out of the steering knuckle was a bit problematic. The Harbor Freight tool operates on a pivot point. Given the length of the ball joint bolt, the angle of the tool arms is quite wide and the upper arm does not sit level on the bolt head (photo). Consequently, when tightening the tool, the top arm of the tool tends to slip off the bolt. Multiple attempts resulted in failure. I tried banging on the bolt with a 3 lb. hammer but was being careful not to hit and damage the knuckle, as clearance is not great. The hammer impacts began to round off the bolt making use of the HF tool even more problematic. I did not want to use heat as the knuckle is aluminum. Hmm… I decided to reduce the angle of the tool arms to increase tool purchase on the bolt by cutting the bolt shorter. This would also leave the bolt surface flat to increase tool purchase (photo). This process took over 20 minutes on the first bolt using my pneumatic cutter as I have a 3 gallon pancake compressor that takes forever to pressurize. On the other ball joint bolt, I did it in under 5 minutes using an electric grinder with cutting wheel. Once cut, I used the HF tool and it worked like a charm. The ball joints popped out in about 5 minutes. Don’t forget to use hearing protection! This approach is also applicable to thrust arm ball joints (assuming you decide to replace the complete thrust arm).
Reassembly was relatively problem free. Aligning one of the control arm bushings in the bolt hole was probably the most time consuming chore. Some adjustment to the level sensor clip made reinstallation much easier than removal. When you tighten the ball joint nut, you will find the ball joint bolt may spin. Dave suggested we lower the control arm/steering knuckle onto a piece of wood to push the ball joint into the steering knuckle to keep it from rotating. We placed the wood on the cast aluminum portion of the control arm to avoid stressing the ball joint cap (photo). Voila! The ball joint stopped rotating and I was able to torque the nut (59 ft-lb). Do not forget to put the washer on the ball joint bolt before installing the nut. Do not torque the bushing bolt until after the car is on the ground and loaded. It helps to turn the wheel to the left when torquing the right control arm bushing bolt (81 ft lb) and visa versa for the other side.
I succesfully passed my inspection so I am a happy camper. I hope these lessons learned are of value to someone doing this job.
Refer to this link for pictures:
http://www.bimmerfest.com/forums/sho...10&postcount=1
