I broke the end off my torsion bar. There are posts that describe this and suggestions what to do. A complete torsion bar replacement takes about 20 man hours and $300 in parts making a $3,000 job. A forum member suggested getting a part manufactured at a machine shop, cut off the end and replace the tip with the machined part. I lost my patience waiting for the part from the machine shop and decided to try another approach.
The tip of the torsion bar broke off at the point where the bolt ends inside (picture below at the point labeled 6). The threads end there but the hole is about 10mm deeper (point 22a). This is all at the end of the bar where the wall thickness is very thin and it a shame Mercedes designed it that way. If the threads went about 10mm deeper (point 22b) or even deeper (point 10) they would catch the full thickness of the torsion bar and it would likely never break. With that in mind I thought I could drill the hole deeper, tap it and put in a longer high strength bolt.
I drilled a hole deeper into the end of the torsion bar. I was surprised how soft the metal was. I expected spring steel and a very difficult job. I used a very small bit to start and worked my way up using 5 bits to an 8.5mm bit (I tried to go straight to a big bit and it just spun and heated). I was able to drill 40mm into the end from the break. Then I tapped the hole with a 10x1.5tap ($5.00 from Levine Automotive or Sears) for about 30mm deep. I carefully tapped and tested several times, patiently and slowly. I bought a 10mmx1.5mmx60mm grade 10.9 bolt ($0.80 from www.boltdepot.com). Then I reassembled the two bushings into the upper control arm front and back, the tip that broke off and the new bolt. The shaft of the bolt was too long (the threading on my bolt was too short) so I had to drill the tip inside shaft a little (point 22c) to let the longer bolt fit all the way in. I used a crow bar to place the control arm in the right place and carefully threaded it all back together. Cost is less than $10. Time took me about 2 hours. It feel and looks like it will be a great permanent fix. It is done! What do you think?
It is a little late, but I would suggest Mercedes retrofit deeper holes and longer bolts.
The tip of the torsion bar broke off at the point where the bolt ends inside (picture below at the point labeled 6). The threads end there but the hole is about 10mm deeper (point 22a). This is all at the end of the bar where the wall thickness is very thin and it a shame Mercedes designed it that way. If the threads went about 10mm deeper (point 22b) or even deeper (point 10) they would catch the full thickness of the torsion bar and it would likely never break. With that in mind I thought I could drill the hole deeper, tap it and put in a longer high strength bolt.
I drilled a hole deeper into the end of the torsion bar. I was surprised how soft the metal was. I expected spring steel and a very difficult job. I used a very small bit to start and worked my way up using 5 bits to an 8.5mm bit (I tried to go straight to a big bit and it just spun and heated). I was able to drill 40mm into the end from the break. Then I tapped the hole with a 10x1.5tap ($5.00 from Levine Automotive or Sears) for about 30mm deep. I carefully tapped and tested several times, patiently and slowly. I bought a 10mmx1.5mmx60mm grade 10.9 bolt ($0.80 from www.boltdepot.com). Then I reassembled the two bushings into the upper control arm front and back, the tip that broke off and the new bolt. The shaft of the bolt was too long (the threading on my bolt was too short) so I had to drill the tip inside shaft a little (point 22c) to let the longer bolt fit all the way in. I used a crow bar to place the control arm in the right place and carefully threaded it all back together. Cost is less than $10. Time took me about 2 hours. It feel and looks like it will be a great permanent fix. It is done! What do you think?
It is a little late, but I would suggest Mercedes retrofit deeper holes and longer bolts.