79 TD rythmic thumping on left turns? - PeachParts Mercedes-Benz Forum

vstech · #1 06-12-2007, 10:17 PM

it sounds like something is hitting the floorpan of the car on left turns, like the tire. the SLS is holding level, and it JUST started. bumps are smooth, no noises. the car handles just great. I am thinking it must be something in the swaybar system, has anybody got any ideas? how about where to start looking?
THANKS!

Biodiesel300TD · #2 06-12-2007, 10:34 PM

I had a similar noise. It ended up being that the tie-rod end on the drivers side was hitting the wheel wieght. Kind of a flooke thing, but might look at the clearence between the tie-rod end and the rim and wheel weight.

It could also be a bad half shaft, probably more likely than the tie-rod end. Also check all your exhuast hangers.

Sway bar links make clunking noises going over bumps. So those are probably fine. But can't hurt to check. Pull them off and if the boots on either end are torn or missing or the pivot point it floppy or loose it's bad. The pivot should be stiff.

vstech · #3 06-12-2007, 10:40 PM

I will put the car up on the lift tomorrow afternoon, I hope it's not the shafts, but I have a few spares so no big deal if it is. the noise is definately in the rear, so unless there are some tierods back there I am unaware of... of course, I don't know much about the rear suspension on these cars yet... I may make a recording of the noise, if I can't see anything out of place on the lift. maybe strap a camcorder under there and see what I see.

Douglas.Sherida · #4 06-13-2007, 06:20 AM

I would guess half shafts.

My 85 300TD did exactly that on right turns.

vstech · #5 06-13-2007, 08:54 AM

well, the lift is crowded today... gotta get that pickup bed off of it first. anyway, I crawled under the car (now that it stopped raining) and the boots are undamaged. it's possible that the joint has failed without damaging the boot, but I doubt it. ya can't see much from just looking under the car while it's sitting on the ground. anybody got any more hints to look at?

d.delano · #6 06-13-2007, 09:51 AM

you probably won't see anything till the car's up if it's the halfshafts- you may have to turn the wheels and really scrutinize the boots
sometimes however it's the Z-links in the back that can make that kind of racket

I had a loud banging happening after I drove about 30min- if I were to stop for a few, after going again the noise would start back up. It was the axle on the pass side. Sounded like a little leprechaun clinging to the bottom of my car, banging on the frame with a rawhide hammer. I replaced both with CVJs and they have been silent ever since- 4 years.

NC Benz · #7 06-13-2007, 10:31 AM

Quote:

Originally Posted by vstech

well, the lift is crowded today... gotta get that pickup bed off of it first. anyway, I crawled under the car (now that it stopped raining) and the boots are undamaged. it's possible that the joint has failed without damaging the boot, but I doubt it. ya can't see much from just looking under the car while it's sitting on the ground. anybody got any more hints to look at?

I am all EYES

and EARS

on this one. I have the same problem.

vstech · #8 06-13-2007, 01:19 PM

driving it around today, I scrutinized the sound. ONLY on left turns, only if there is body roll to the turn. smooth turn, no noise, hard turn noise, long sweeping curve at highway speeds, no noise, unless I pull the left hard, then the noise reappears, *(really fast thump at 80MPH...) so it is definitely axle/wheel related noise. it sounds like a grating thump, like squish..THUNK squish...THUNK... faster I am going, the faster the thump.

captainmonk · #9 06-13-2007, 02:08 PM

my axles started out just that way until it got worse and did it all the time

vstech · #10 06-13-2007, 02:13 PM

well, if it's the axles, I will be surprised. there is NO evidence of rips or tears in the boots, and there is NO evidence of oil/grease on the body anywhere... nice and dusty under there. I can't wait for the lift to free up.

#11 06-13-2007, 02:19 PM

Quote:

Originally Posted by vstech

well, if it's the axles, I will be surprised. there is NO evidence of rips or tears in the boots, and there is NO evidence of oil/grease on the body anywhere... nice and dusty under there. I can't wait for the lift to free up.

One of my CV joints was bad with the boots intact, they do wear out. I had the same symptoms, mine would make a very slight "thump-thump" noise in long right turns (I could only hear it if I was coasting with minimum engine noise). I replaced them both before it got any worse.

rhodes2010 · #12 06-13-2007, 06:02 PM

One of mine had a turn only noise too. Luckily it cost next to nothing
and was not severe.

At the rear wheels, on each side, the thing that connects the rear sway bar to the swing arm. Maybe 6 inches long.
The connector broke and was whacking something only while in a turn.
Only one side was broke, and it only made noise while making a turn on one
direction.

Early ones are metal, later ones are plastic. Both do the same job.
They are interchangeable.

Took all of ten minutes to fix.

linguica · #13 06-13-2007, 08:11 PM

Not sure where exactly the noise is coming from, but could also be shift linkage bushings. Linkage will flop to the right and hit the drive shaft when turning left. Just another possibility. Good luck.

vstech · #14 06-16-2007, 08:50 AM

well it looks like I was correct in my original diagnosis. it is the sway bar system. thanks to the poster with the mention of the links... left side one was separated at the tire end of it. and it bangs against stuff on left turns... it also drags against the tire on occasion. I will change it when the new ones arrive.

#15 06-16-2007, 04:07 PM

Quote:

Originally Posted by vstech

well it looks like I was correct in my original diagnosis. it is the sway bar system. thanks to the poster with the mention of the links... left side one was separated at the tire end of it. and it bangs against stuff on left turns... it also drags against the tire on occasion. I will change it when the new ones arrive.

Good news, a lot cheaper than half shafts.