Weird Front End Rattle?!
 

Hey folks,

Normally I'd do my best to sift through everything you've kindly contributed here, but I'm caught between a rock and a hard place and need to jump on this problem quick. I'm hoping that I can provide enough info to diagnose this: Money is beyond tight and I'm hoping to hit the nail on the head.

The car in question is a 1982 300SD. After taking the car to a local friend he pronounced one tie rod as bad, but the rest of the front end as being tight and in great shape. I replaced both tie rods, and took the car for a drive...

And the rattle is still present. By rattle I mean:

Go over a bump and you hear a rattle. If I hadn't replaced the tie rod, I would have thought that it was worn. Further symptoms include:

Bumps=rattle. Cruise at any speed over 50, and randomly the front end starts rattling, making me think of a busted shopping cart wheel. It doesn't rattle all the time on the highway, but intermittently.

Here's the weird part, and I'm hoping this helps pinpoint the issue: step on the brake and the rattle stops. It goes away entirely. Take your foot off the brake, and poof, rattle comes back. It's focused on the left side only.

I know that trying to diagnose suspension issues through text is akin to using a Ouija board - I only have enough money to spend on one parts purchase this week, and I'm hoping to hit the target the first time. I don't want to hurt the car by driving it in this condition.

With many thanks,

-James F. Smith

guide rods.
not a difficult repair, but there are specific orders to follow in changing them. you will require an alignment after.

Sound like a guide rod bushing. Pretty simple fix on the W126 chassis.

With the car off the ground grab the front wheel at 9 and 3 O'clock and pull forward/rearward. Look for movement in the rod that extends to the large bushing in the aluminum casting.

The casting can be removed by removing the three bolts per side on the rear cross brace, then remove the three large casting bolts. Loosen the clamp on the rod and count the number of turn it takes to get it loose from the bushing. Install the new one the same number of turns to get the alignment close.

With the casting off you remove the bushings rear cover (four allen bolts) then drive the bushing out with a hammer.
Use a large hose clamp around the new one to compress it to get it started in the casting. The cover bolts will press it in the rest of the way.
Make note if there is a drain groove on the new bushing. It goes toward the bottom.

Good luck.

Many thanks for the quick reply! I'll see if I can find the procedure here for replacement. The thing that was throwing me for a loop was how it would outright stop when I used the brake. I couldn't imagine ball joints or control arms stopping rattling when the brake was applied.

-James F. Smith

Applying the brake compresses the guide rod bushing taking up the (rattling) slop.

I think I've posted some pictures of the procedure. Use the search button might find my posting.

This forum is simply amazing and has saved my bacon a million times.

Thanks again for all of the help and quick responses; looks like I'll be shopping for the guide rod kit; with luck Massachusetts will give us a few good days of weather and I can get back to driving, as opposed to rattling down the road.

-James F. Smith

For those looking for Whiskeydan's procedure / photos, you can find them here:

http://www.peachparts.com/shopforum/showthread.php?t=145762&highlight=guide+rod+whiskeydan

Again, thanks for the help!
Best regards,

-James F. Smith