Pagoda SL Group

W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: jedwards on March 06, 2014, 06:41:58

Title: Suspension or Exhaust knock?
Post by: jedwards on March 06, 2014, 06:41:58

Gentleman,
I have an early but low mileage RHD 250SL Auto and I have a noise that comes from either the suspension or the exhaust, but only when I run over small “sharp”  items like man-holes, pot-holes or cats eyes.  Anything larger that exercises the suspension itself is perfectly quiet.  I cannot replicate this effect from under the car, so not sure quite where to start.

To my ear, the sound is quite “light” as if the metal baseplate on the front discs is hitting something.  Its is certainly not a heavy metal “knock” that I would expect from severe suspension wear.  It appears to come only from the exhaust side (right) of the car and only after the  car has been driven for more than 10 minutes.  It is usually occurs there the front right shell runs over something small,  but sometime from the back wheel as well, but always the same metallic “clank”

To me it sounds like the  exhaust knocking on something,  but I cannot work out what it could be. The exhaust is in very good condition and all rubbers are good and in place.  I’ve pushed on the  underbody head shield, but that seems secure.  I’ve pushed and shoved the exhaust about by hand, but cannot replicate any contact is noise.

Other than paying someone a few hundred dollars to go over the suspension, are there  any suggestions about what I can do at home and without a hoist?
Hopefully, someone else has experienced a similar problem and can help with some advice.
Title: Re: Suspension or Exhaust knock?
Post by: J. Huber on March 06, 2014, 15:03:52
Could it be a worn out differential mount (the one in the center of the trunk area?). Sorry I cannot think of the actual name, but they eventually get worn and start making a clankin' sound...
Title: Re: Suspension or Exhaust knock?
Post by: scoot on March 06, 2014, 15:24:39
My 250SL has a banging sound when I go around a corner at low speeds.  Or do donuts in a parking lot.  I was able to reproduce the sound by grabbing the exhaust pipe on the car and shaking it.  Still haven't fixed it but at least I know what it is.
Title: Re: Suspension or Exhaust knock?
Post by: sarasotasl on March 06, 2014, 17:38:41
Had the same issue for about a year.  It is the differential mount in the center of the trunk.

Good luck!
Title: Re: Suspension or Exhaust knock?
Post by: gkaiser on March 06, 2014, 17:47:26
Agree it's probably the differential mount.  It can properly be installed in one way but some mechanics believe the bolt holes are wrong and bore them out to make it fit the wrong way.  Might check that.
Title: Re: Suspension or Exhaust knock?
Post by: Bonnyboy on March 06, 2014, 17:51:12
I had a very curious knock that turned out to be a loose brake caliper.  The securing tab on the bolts were not bent over and the bolt loosened off just a hair - enough to give a bit of slop.

I checked everything underneath a hoist with a wooden sitck and a mechanics stethiscope and found nothing (found other items to repair but not the knocking).  Then I took off the wheels and hit the brake caliper with my stick and I heard the "knock" through the stethiscope.  Voila.  My method is to stick the end of the mechanics stethiscope onto a piece of metal and then hit that metal slightly with a piece of 1' dowel (18" long).  You should be able to hear the knock if there is one.

 
Title: Re: Suspension or Exhaust knock?
Post by: Essell on March 06, 2014, 19:42:27
Going around a corner or doing a donut might induce rumble from a bad wheel bearing. Essell
Title: Re: Suspension or Exhaust knock?
Post by: jedwards on March 07, 2014, 09:36:17
Is there a test I could do to check if the problem is the differential mounts?

Jeff


Title: Re: Suspension or Exhaust knock?
Post by: WRe on March 07, 2014, 09:44:53
Hi,
see here: http://www.sl113.org/forums/index.php?topic=18561.0
...WRe
Title: Re: Suspension or Exhaust knock?
Post by: jedwards on March 08, 2014, 04:13:11
Thanks to you all.
I founds this link :  http://www.sl113.org/forums/index.php?topic=806.0
which told me everything I needed to know about how to check it and you were absolutely right.
I've ordered a new one and we shall see how it turns out.
Thanks a million, as always.