New, very sporadic noise from front of w124 - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 09-19-2013, 07:18 PM

I have a relatively new, and extremely sporadic, pop coming from what seems to be the left front wheel area, which I've been trying to pinpoint and could use some suggestions beyond what I've suspected and checked. I've been trying to catch it on video but I can't seem to purposely recreate it.
I would describe it as somewhere between a pop and a clunk. It only happens once-in-a-while on certain fairly sharp, low-speed right-hand turns, or when straightening the wheel from a right-hand turn, usually when I'm lightly on the brakes ... such as pulling into a parking space or backing out of one. Occasionally I get the same sound from the same area when accelerating quickly from a stop going straight, but mostly just the turns. It does not make a constant sound, or grinding or creaking or groaning. Just pop and that's it. Maybe two pops. It does not do it with the car sitting still no matter how much or how rapidly I turn the wheel. And it does not do it consistently. Most of the time pulling in and out of parking spots or lots it doesn't happen. I can't figure that formula that makes it happen. It does not happen going over bumps or potholes.
I have tried bouncing the front of the car up and down, no sounds. Tried rolling it back and forth, turning the wheel, no sounds.
I checked tie rods, drag link, ball joints, springs and shocks visually, as well as sway bar. I can't feel any play in the ball joints ... tried putting a pry bar under and lifting up with the wheel off the ground. Calipers are on tight, and brake pads (though looking due for a change) don't seem loose. Bearing play seems normal. No noises from tugging on and wiggling around wheel in all directions.
I found a loose sway bar bracket bolt in the front but tightening it did not stop the pop sound.
I checked to make sure the steering box was not loose, and checked other components in engine compartment for looseness. Engine mounts are good and bolts down tight. No loose bodies in the engine compartment.
Stuff I'm thinking it could be:
-loose brake pad ... have to change these anyway so I'll see if that makes a difference
-sway bar bushings ... they look fine, but have a lot of orange powder around them ... maybe just worn?
-door check ... really sounds lower-pitched than a door check sound, but it's possible it's coming from the driver's side door check.
-shock or shock mount. Shocks don't show any other symptoms. They were changed about 40k ago, but the mounts were not changed (I had a shop do it ... wish I'd thought to tell them to replace the mounts and bumpers).
-steering box internals?
Any other thoughts of things to check? I'll take off the steering shock and push it by hand but I'd think noise from that would occur more consistently.

Stretch · #2 09-20-2013, 12:17 AM

I know you said you checked them - but my vote is to check for enough grease / evidence of water / much / junk in the ball joints. Give the boots a good squeeze and see if you get some yucky mingy puss coming out...

Zulfiqar · #3 09-20-2013, 08:48 AM

That noise is usually the ball joint, checking them is a chore, you need to compress the spring somehow and lever the entire wheel to feel wear.

If it were my car - I would change them out just on their age. I made a thread on my homebrew ball joint tool which works a treat and does not require 3 hands or any "colorful" words.

BodhiBenz1987 · #4 09-20-2013, 12:34 PM

Thanks guys. I will re-check the ball joints. That is my top concern considering the consequence of complete failure. They look good but I'll poke around the boots more. Zulfiger, how about, with the car up on jackstands, putting a scissor jack under the LCA to compress spring, then moving wheel around? I could do that while changing brake pads.
The ball joints have about 100,000 miles on them, for whatever that is worth. I guess old enough that they could be suspect, but not so old that I'd immediately assume they are bad. I was thinking they are something I might change relatively soon anyway as preventative maintenance.
I think I'll just replace the sway bar bushings too, anyway, since they're easy and not horribly expensive.

Walkenvol · #5 09-20-2013, 01:16 PM

Quote:

Originally Posted by BodhiBenz1987

The ball joints have about 100,000 miles on them, for whatever that is worth.

I'd change those whether it was the source of the noise or not, but as said before ball joints are the most common source of front end noise.

Stretch · #6 09-20-2013, 03:04 PM

Here's a link to the W201 chapter on startek that shows how you're meant to check for wear - this might give you some idea on where to position your crow bar!

http://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/10005.pdf

(W124 manual is also available on startek but harder to access)

BodhiBenz1987 · #7 09-20-2013, 04:13 PM

Thanks, Stretch! I have a print w124 manual so I'll check that too ... I thought it only had R&R procedure but I'll doublecheck.

Stretch · #8 09-21-2013, 03:35 AM

Well it isn't 100% helpful because it shows how to check for wear with the suspension in bits - however it does show the direction in which play should be checked. Someone recently posted up a moving GIF image showing how to check for ball joint repair on a different model - I can't remember where I saw it though. Could have been BW could have been here on the vintage forum...

...sorry if the grey cells kick back in to gear I'll post the link. I think the GIF was borrowed from a German site anyway...

colincoon · #9 09-21-2013, 03:43 AM

It was me, in the Febi parts thread.

BodhiBenz1987 · #10 09-21-2013, 01:56 PM

So, in the GIF, the jack could be placed under the jack point? Just making sure I'm looking at it right. That's a very helpful image ... I was putting the prybar on the other side of the wheel. I will play with it while I have the car up to do brakes later today.
I did doublecheck the boot visually, squeezed and pushed it around ... nothing leaking out and the rubber looks good.

Stretch · #11 09-21-2013, 02:18 PM

Quote:

Originally Posted by colincoon

It was me, in the Febi parts thread.

Yep - that was it - well done that man!

Quote:

Originally Posted by BodhiBenz1987

So, in the GIF, the jack could be placed under the jack point? Just making sure I'm looking at it right. That's a very helpful image ... I was putting the prybar on the other side of the wheel. I will play with it while I have the car up to do brakes later today.
I did doublecheck the boot visually, squeezed and pushed it around ... nothing leaking out and the rubber looks good.

Yep jack or better still an axle stand under the jack point. If you do a jack make sure you have three wheels on the ground you might have to give that wheel some wellie to see / feel / hear some movement in the ball joint.

BodhiBenz1987 · #12 09-22-2013, 02:22 PM

I replaced the brake pads and no change (figured that was unlikely the source, but they looked pretty sorry so it was time for a swap anyway).
I played around with ball joint testing for quite a while last night and still don't think I'm doing it right. It was hard to lever the wheel in the way the video showed because the bottom of the pry bar wouldn't hold at that angle just slip across the floor ... I put it more under the wheel and I think created a similar action. Could not see any movement in the ball joint or noises. If my indy has time, maybe I could take it in to him and have him look, since I'm not sure if I'm doing it right.
Also, I noticed a very loud noise when turning the steering with both wheels off the ground. Just from this side. It is slightly different pitch from the noise I get while driving, but maybe the same source. I tried to locate it specifically using a auto stethoscope, and it sounds like it's coming from the shock. But I'm not sure because I realize sound could be carrying up the shock. When I put the stethoscope probe right on the ball joint or tie rod end, it's not any louder. Very loud when I put it on the shaft of the shock.
Here's a video: 87 300D steering/suspension noise - YouTube
This particular noise is not present with the wheels on the ground.

Stretch · #13 09-22-2013, 04:31 PM

Chasing sounds around structures like that can be tough.

If I were you I'd break the joint on the tie rod to steering arm and see if just turning the (road) wheel by hand reproduces the sound. If you get the sound when you turn the steering wheel with the tie rod detached then you know it is that away...

(try not to break the boot on the tie rod - or you'll end up fixing more than you bargained for - don't ask me about this type or occurrence...)

(My guess is idler arm or steering damper <= just for fun!)

Zulfiqar · #14 09-23-2013, 09:01 AM

Another way to confirm the joints are bad (but have good alignment) is to turn the wheel full lock and move the car forwards, it should want to return to centre with real force.

If it wants to stay there the joints are really bad.

After replacing the joints you will also not feel when the car goes over bumps, it somehow softens them out too.

BodhiBenz1987 · #15 09-23-2013, 03:53 PM

Quote:

Originally Posted by Zulfiqar

Another way to confirm the joints are bad (but have good alignment) is to turn the wheel full lock and move the car forwards, it should want to return to centre with real force.

If it wants to stay there the joints are really bad.

After replacing the joints you will also not feel when the car goes over bumps, it somehow softens them out too.

It is pretty keen on returning toward center. If I put it in full lock and let go, it bounces a few degrees back towards center without the car even moving. When the car moves forward, it keeps centering pretty fast if I don't hold on to the wheel. I had an alignment last about a year ago and it tracks great.
As mentioned I think I'll have my indy take a look. If the ball joints are good now, I'd rather not rebuild the front end until winter, when I don't drive the car as much anyway (i.e., best time to have it off-duty for a while). Obviously if they are dodgy, I want to replace ASAP.