Significant clunk/rattle on right front

[Tom in seattle]

I have suspected wear in the right front suspension but in reading the tech manual I’m not sure it is the suspension.  I’ve jacked the right side up and tried to find looseness by wobbling the tire but cannot detect movement.  Now I’m wondering if subframe mounts could be the issue understanding that the rubber falls apart and the fact that this came on suddenly.

Have had this problem, done the work?  How do I narrow this down?

[roymil]

First, you can inspect the front subframe mount fairly easily.  With the wheel off, you should be able to see the side from inside the wheel well and possibly tell about the condition.   Also you could pull the cover plate off from inside the engine bay to see the top of it.  Four bolts hold the cover plate on.   On mine, the rubber had completely decayed and the center bolt was able to move and push up on the underside of the plate.   I found a cross section picture in the BBB that might help.   Replacement isn't too bad with an assortment of jacks and the good directions on this site, but it is a tight fit.  I removed the shocks and brake lines to allow the body to be separated far enough from the subframe cross member and allow room to exchange with the new mount.  good luck!

[Garry]

Tom,


I had a clunking/ rattle in the front right of the car every time i went over rough road.  Took me ages to finally find the problem, a broken raditor mount.  As does happen, it was the last thing that i pulled apart or looked at in my frustration 😬😬🫣


Garry

[austinado16]

.

[Tom in seattle]

I have tried to “wobble” the wheel while jacked up, but only from 12 to 6.  I will try again.

[Tom in seattle]

I will attack this today.  On the diagram you posted is #4 the rubber part and is this component still available?

[Tom in seattle]

I know what you mean. My rattle is a heavy metal to metal one which suggests something major.  Thanks for your help.

[Jonny B]

The subframe mount is available from the usual cadre of suppliers.

[roymil]

yes, the shaded area represents the rubber part of the mount.   When jacking just the wheel and subframe by themselves the damage might not be obvious because the body rides on top, but if you carefully jack up the body only, letting the wheel assembly hang a bit, (again, carefully!) then you may be able to see the mount separate at one of the rubber interfaces and the damage will be clear.   Parts are available.  i found this on Bud's site but I'm sure most of the usually sources have them.  I think I bought mine from the Mercedes classics center but cant remember for sure.   There's been some discussion about the rubber quality of various engine mounts and related parts on this site that are worth reading through.  I have no opinion though.

[roymil]

I just took a peek and actually you don't need to jack the car at all to see the subframe mount from the front.   You can see the gap between the upper and lower metal portions with the new intact rubber in between.  My old one was collapsed and when I lifted the body you could see the mount seperate.

[Tom in seattle]

I have taken the 4 bolt cover off and see the large long bolt.  If I remove this bolt and lift the frame will this allow me to remove and replace the rubber piece?

[austinado16]

.

[roymil]

I think thats basically it but i'm pretty sure you'll need to remove the flex brake lines and shocks as well as making sure everything else around the engine can move too as the block drops with respect to the radiator for example, and also the air filter housing flex pipe to the intake manifold may need removal among other things.  I'm not completely sure because I also had a lot of that stuff removed at the time I changed mine.   Make sure to read through instructions on this site as well as BBB and/or Haynes.

[Tom in seattle]

If I did this correctly I’ve attached a photo of one of the two front subframe mounts showing a large crack in the rubber.  I have jacked the frame up suspending the wheels.  The retaining  bolt and washer in the center of the sub frame rubber visible from the engine bay drops down about 1/2 inch when the frame is lifted. So this clearly explains the noise I hear when going over bumps.  The center bolt is rusted so I’m soaking them in PB Blaster before I try to crank them out.

I think I’ve eliminated the likelihood that any of the steering/suspension components need replacement as I’ve tested them as guided here. 

Thanks all for your help.  I love this website.  I’ll report back as I wind this up.

[ejboyd5]

How old are your shock absorbers?

[roymil]

Good question about the age of the shocks and might as well think about the age of every other piece of rubber on the car too, especially the suspension components.  I just swapped in new urethane sway bar bushings and the improvement is remarkable.  The old ones looked fine until I pulled them off and could see all the deformation and aging symptoms.

I started the "50 year maintenance" plan on my 280SL about 6 years ago by making a long list of rubber bits that looked like they needed replacement.
I tossed the list and have since boiled it down to a 2 point process that has served me well.   If I find a fair price for a rubber part I haven't changed yet, I just buy it.

#1 If it is not made of metal, just replace it. 
#2 if you think you've found an exception to #1, you are wrong.

[austinado16]

Mark, where did you find the urethane bushing?

[Lorsar]

For Todd https://www.sl113.org/forums/index.php?topic=35032.0

[austinado16]

Thank you so much Lori.

[Garry]

We were trying to trace the causes of a rattle in the Front RHS of a 280SL and then we are talking about breaking tubes out of a unibody box frame?? and then the quality of urethane bushing to be used on a W111 coupe sway bar.. I think the thread getting hijacked! and maybe these questions/comments need to go into the W111 thread if thats the question/answers?.

[ja17]

Yes a bad shock can make noise. You might want to look there first. Also do a thorough lube service to see if the noise gets better or goes away temporarily. A dry worn out king pin assembly can be very noisy. A good lubrication grease service will temporarily make the problem go away or make the problem better.

[yves]

I have a rattling noise actualy , in the middle of bulkhead so right for the driver, and found the culprit by opening the air aperture :
It was the metal plate at the back side of the heating radiator .... see the link above:

https://www.sl113.org/wiki/Electrical/HeaterCore
Just an idea...!
Good luck

[austinado16]

We were trying to trace the causes of a rattle in the Front RHS of a 280SL and then we are talking about breaking tubes out of a unibody box frame?? and then the quality of urethane bushing to be used on a W111 coupe sway bar.. I think the thread getting hijacked! and maybe these questions/comments need to go into the W111 thread if thats the question/answers?.

Please accept my apologies Sir.

[Garry]

Todd,


No apologies necessary, we just don’t want to mix up the W11x that has its own area with the W113.