Inner control arm bushings

[BHap]

I have a mysterious "klunk" in the front end of my car and it was suggested that I check the inner control arm bolts.  I am wondering if the threaded bushings (nuts) on the inner control arm bolts are replaceable without disassembling the steering knuckle.  What are the common wear items on the inner control arms?  I will check the torque of the threaded bushings and the bolts securing them to the subframe, but if it is not too difficlut, I may replace the bushings.  Thoughts, tricks and tips appreciated....

Bob Happe
Pittsburgh, Pa
1970 280SL, white/black 4 speed

[JimVillers]

Bob .... I would doubt that the inner control arm bushings would be the cause of your clunk.

Make sure that you know what is bad before you fix it.  Lift the front wheel off the ground with a jack under the spring; this takes all forces off of the front suspension.  Wiggle the tire at 12-6 o'clock positions.  If you feel movement, feel the top and bottom trunion bushings for movement (any movement means replace).  Then wiggle at 9-3 o'clock for looseness in tie rod ends or idler arm bushings.  

Now the answer to your question; I don't think that you can replace the inner control arm bushings without removing the arms (possible but very difficult to control the spring and to reinstall).  The better way is to put the car on jack stands, remove the shock absorber, jack up the lower control arm, compressing the spring, then remove the lower trunion bolt, lower the jack, remove the spring and then un-bolt the lower control arm and remove.  


Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16, MGB 5-Speed

[bpossel]

Hi Bob,

I agree with Jim.

I did try to replace the inner control arm bushings without removing the spring and had no luck, actually almost made things worse...  long story....

As Jim states, remove the spring, remove the arm, then remove each large nut from each side, clean off the old grease, install the new bushings (sealing rings), install springs...

As you may already know...  the inner control arm bushings (sealing rings) are really just a large rubber sleeves, not really a bushing.  These rubber sleeves just assist to hold in the grease.  You can actually run without these sleeves.  Just need to grease the joints more often...

Good luck and keep us posted...
Bob

Download Attachment: controlarm.jpg
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bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[enochbell]

Bob,

I would check the torsion bar bushings, the shock absobers (both for compliance/resistance and for integrity of rubber mounts) and the subframe bushings, in that order, to rule out other sources of "clunk".  I think the control arm bushings would have to be worn to the point of presenting dangerous control problems by the time they started to give you a clunk.

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[waqas]

Interesting... I too have been trying to track down a mysterious 'clunk' from the front suspension. I replaced all the torsion bar bushings, the subframe mounts, the two motor mounts... all to no avail. The clunk remains the same. I know my shocks are dead, but why would they cause a 'clunk' when there is a change in horizontal momentum? (the car is not bottoming out, just starting from rest...)

I won't get the new shocks for a bit, however other things I'm considering are the leaf-spring rubber mounts (which are allegedly very expensive!), as well as the front spring pads.

Don't know if this helps, but I'll bet there are some fairly common sources of the dreaded front-end 'clunk'...

WAQAS in Austin, Texas

[harleydan]

Could a bad kingpin be a contributing factor for the "klunk"?

Danny

[mdsalemi]

Gents,

I had a mysterious klunking which turned to creaks and groans and other eerie sounds.  Lived with it for 2 or more years,  checking everything in the suspension.  The car had been into 3 different shops and nobody was able to track it down.  At Dan's last year it got so bad the next morning I drove it to Motorwerks where we once again went through everything.

Turned out to be the sway bar mounts.  They LOOKED tight and bottomed out so nobody actually took a wrench to them.  Take a wrench to all 4 of your and ensure they are tight to rule that out.
Once we did that the suspension is PDQ.  Pretty Darn Quiet.

Also don't rule out muffler parts hitting places they are not supposed to hit.  Ensure all your rubber donuts are new.  They don't last very long, just a few years.

Michael Salemi
1969 280SL
Signal Red 568G w/Black Leather (Restored)
President, International Stars Section
Mercedes-Benz Club of America

[BHap]

WAQAS, I have the same symptoms - will "clunk" when starting out from a stop, but will not repeat every time. If I slow down and then accelerate will sometimes repeat... I replaced kingpins last summer, motor mounts, trans mount, diff mount, trailing arm bushings and still it clunks...  not a huge issue, but one i'd like to identify....  flex disc is good, subframe bushings done a few years ago... will examine the torsion bar bushings, shock mounts, spring perches etc..  for now I think I will make sure the inner control arm nuts and bolts are tight, grease everything up and keep listening...  thanks for the suggestions....

Bob Happe
Pittsburgh, Pa
1970 280SL, white/black 4 speed

[JimVillers]

Bob ... While not in the front, the center differential mount (in the trunk) will cause a nice clunk.  Since these are unique to Pagodas, most mechanics never check it.  This has been covered many times before so you can search for more details and pictures.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16, MGB 5-Speed

[tuultyme]

I had a "klunk" in my right front which disappeared when I replaced the shocks which also raised the car just a little.

Bruce; 268Blaugrun(green) 1970 280SL; IL

[waqas]

Bruce, that might explain my 'clunk'. (my shocks are effectively ornamental until I get new ones). But why would new shocks raise the car? Don't the springs serve as the support for the car? (with shocks as dampers only) Are new shocks pre-adjusted for a particular height? Now I need to go watch Jim Villers' video on "shocks and springs" again to get my head straight...

WAQAS in Austin, Texas