W123 Suspension Noises - PeachParts Mercedes-Benz Forum

Southwest1124 · #1 10-16-2019, 01:08 PM

Hello,

My '85 300D has been making two intermittent noises from the rear and I need some help finding out what it could be. The first and most often noise is often a semi hard clunk, always when hitting a bump and in other situations that oscillate the suspension. I was told to check the drive shaft support bearing, would a replacement one be the right move? Is it something else? The second noise sounds like someone hit a guitar chord, but it only rings for a second? This "ringing" ONLY happens when turning AND hitting something/going into driveway etc. For this I was told on another forum as well that a wheel bearing could be the cause? Does this make sense, also how would it cause this noise? I am curious the source of the noises and how important it be fixed quickly. I have done all 4 shocks in my ownership (shocks about 4 years ago) and replaced all 4 coils (about 2 years ago) as well. ALSO, I replaced a rear lower control arm about a month ago, noises were there before and after that job. I am 12 months from graduating with an engineering degree, and plan on doing all bushings when I have a real job and can let the car sit at a shop. For now I have to pick my battles for what repairs fit in the budget.

Hopefully this is not too rambley, but here are my questions again after reading the situation

1. What could be causing these noises?
2. Can it be driven as is?

Thank you!!

t walgamuth · #2 10-16-2019, 02:57 PM

Have you put car on a lift and looked for signs of deterioration of rubber bushings?

optimusprime · #3 10-17-2019, 06:00 AM

Lift car on 4 poster and spray all rubber bushes gaiters -everything with rubber on or in with silicon spray .The rubber dries out over time to make these noises .But if the bushes are worn you will need to replace them .

Alec300SD · #4 10-27-2019, 12:46 PM

Quote:

Originally Posted by Southwest1124

Hello,

1. What could be causing these noises?
2. Can it be driven as is?

Thank you!!

Sounds like one or more failed balljoints on the white Delrin plastic connecting rods between the rear swaybar and the caliper carrier.
Could also be a cracked connecting rod for the rear swaybar.

I had exactly the same symptoms of a rear clunk when turning into a driveway.
Just did this repair on 'Desert Rose' yesterday and soon will be posting a DIY pictorial.

Probably shouldn't drive the car agressively until it is repaired as the rear tracking may not be stable.

Diesel911 · #5 07-22-2020, 03:45 PM

Despite the Shocks being done 4 years ago I would see if the shock shaft nut needs to be retightened incase the rubber isolators have become compressed and now loose.

My Car is an 84 and I was not having you symptoms but the rear control Arm Bushings and in particular the Sub Frame Bushings were no good. I have about 250 K on it.

Besides the Plastic Links the rear sway bar has rubber bushings on the Frame. The front also has bushings but on the fire wall.

You are likely dealing with 35 year old rubber and the mentioned plastic parts.

JHZR2 · #6 10-16-2020, 11:05 AM

I’m not sure those are bearing noises. If a bearing was clunking or twanging, I’d suspect it would rapidly fail...

I’d bet on the sway bar being the culprit in some way, but other mounts could be the case. A subframe mount that has decomposed has a few good opportunities for that kind of noise. A bad diff mount might be a culprit too, as it could get moved around, but I’d think that if it were that bad, the mount would shift around in other use..l

240D.Bill · #7 11-01-2020, 01:34 AM

Quote:

Originally Posted by optimusprime

Lift car on 4 poster and spray all rubber bushes gaiters -everything with rubber on or in with silicon spray .The rubber dries out over time to make these noises. But if the bushes are worn you will need to replace them .

I’d caution against the use of silicone spray for one reason. You never know what your getting when you buy a can off the shelf. Many of the consumer available products marketed as “Silicone Spray” contain petroleum solvents and propellants that quickly degrade rubber/elastomers and plastic/polymers.

100% silicone grease/oil(siloxanes) is safe for nitrile and butyl rubber. It’s the other components that may present a real problem.

Just sayin... I learned that the hard way, as in ‘rubber embrittlement‘.

JHZR2 · #8 11-01-2020, 11:24 AM

Quote:

Originally Posted by 240D.Bill

I’d caution against the use of silicone spray for one reason. You never know what your getting when you buy a can off the shelf. Many of the consumer available products marketed as “Silicone Spray” contain petroleum solvents and propellants that quickly degrade rubber/elastomers and plastic/polymers.

100% silicone grease/oil(siloxanes) is safe for nitrile and butyl rubber. It’s the other components that may present a real problem.

Just sayin... I learned that the hard way, as in ‘rubber embrittlement‘.

Excellent point.

DOT 5 brake fluid is not glycol based - it is silicone oil. That can work - used it on the subframe bushings on my old BMW 318.

Alternatively, Super Lube sells silicone oil with PTFE on Amazon.

Totally agree to avoid the petroleum distillates. Some folks use sprays by spraying on a rag and letting the solvents flash off. But that doesn’t work well for spraying suspension parts.