w126 'Thumping' front end
 

Hi,

I have rebuilt most of the front end of my 126 in an attempt to cure a thiumping noise I get when travelling over rough surfaces.

The parts I have replaced include:-

Lower ball joints
Upper control arms
Bilstein Shocks
idler arm bushes
track rods
Steering damper

I am now running out of things to replace and yet the thumping is still there.

Anybody had this problem b4?

regards,

Alex

Oh, and also...
 

I forgot, it has a new drag link too...

How about doing the front sway bar bushings as well. A lot of people report thumping cured after replacement.
Good Luck

Hi
 

Im in the UK so some of the mechanical terms you use may be different here. Im not being facetious, but could you explain what you mean by sway bars? Are you meaning what we call lower control arms that govern castor angle??

Thanks,

Alex.

The 126 front end contains some non conventional nomenclature. My first guess from the complaint is what I call the caster joints, sometimes refered to as rear lower ball joints, sometimes refered to as longitudinal strut pivots. The problem is that the lower control arm on these cars is a concept composed of numerous pieces.

You mention track rods....but, does that mean that you changed the track rod/brake strut/guide rod/etc. MOUNTS? I ask because (as you may already know) the rods themselves can be changed while NOT changing the mounts.

This sounds like a classic guide rod MOUNT issue.


ACK! Evil post alert! :D

Track rods
 

By track rods, I mean the entire rod and the balljoint ends.

The lower balljoints have also been changed, which was a pig of a job as it's damned near impossible to drive them in squarely.

Re: Track rods
 

A Steve and Chris mentioned, the track rod ball joints fit into a mounting block that itself has bushings that attach it to the frame. One of these bushings will get more that its share of power steering effluent if there's anything of a leak in the steering box. Plus they also wear over time.

The sway bar is the ~3cm tube that attaches the upper control arms on both sides of the car. There are bushings on the outer edges of the longitudinal section of the sway bar, and bushings on the ends where they fit into the upper control arms.

Sixto
95 S420
87 300SDL

Thanks
 

OK!

Well the sway bar is what we limeys call the anti-roll bar. I changed the bushes for the upper control arms when I put new ones in. How do you check for freeplay in the sway bar bushings?

I will check the track rod mounts as you have suggested.

Cheers and thanks again.

Alex

If you haven't changed the trackrod mounts (that's what it appears you're saying now), then that's where my bets lie. :)

Chris
'85 300SD

LOL - not to make lite of the situation but I had to LOL when I read that. There is a tool made for this procedure that makes this particular task pretty easy.

Lower Ball Joint
 

Well, you live and learn.

My local MB main agent wouldn't do the job as they didn't have the tool and so would only sell me a complete arm with the BJ in-situ.

I nearly broke my thumb knocking the old ones out with a 4lb lump hammer, I manufactured a drift out of a large impact socket that I shaved an angle off to make it sit square against the base of the BJ.

Where do you get the tool???????

Cheers,

Alex