1. Consider demounting the front tires and check for any wheel weights or old valve stems inside. Alternatively, try rotating the tires rear to front and listen for any change.

2. Retorque the bolts joining the front hubs to the rotors.

3. Retorque the caliper attachment bolts.

4. Retorque the wheel lugs.

5. With our non-floating calipers, if there is excess clearance between the caliper piston and caliper body, the piston may "rock" or chatter, inducing a noise coupled through the rotor/hub assembly. When brake pressure is applied, the clamping effect between the piston and rotor effectively eliminates any clearance. This is a remote possibility since you do not describe any pulsing sensation through the brake pedal.


Good luck with your troubleshooting effort.

__________________
Blair Tyson
1985 300D
300,000 + miles

When I read your first post I was litterly yelling at the moniter- Its the Idler!!!!!!!!!! Then I read on down and see some one has beat me to it. I have had this happen on several cars- The thing goes south and does exactly what you described. It some times doesnt appear to be bad- but it only takes a slight bit of movement to cause this condition. You can buy a rebuild kit very reasonably to check it out.
Chris

I'm going to add my car to the list of "clunkers". i just bought an 85 300SD that does the same thing on the gravel road out to the pavement where i live. steers and drives fine, just makes this noise on the gravel.
and....
someone doesn't know what a "washboard" road is???? wow. i would ask: why does a car rust? nothing here does.

__________________
1985 300SD
1998 Jetta TDI
Previous: lots of diesel VW's, MB's, KW's, Pete, Freightliner


Walking isn't a lost art: one must, by some means, get to the garage.

Mark,

Lot of guessing here... But maybe you have a bad shock on that side. You might try to swap it with the other side to see if the noise will follow it. Also when you installed your Bilsteins, did you make sure the top washer that is dished has the dished part facing up? A common mistake is to have it facing down and when the bushing is compressed from the road bumps, the top washer knocks against the body.

__________________
1983 123.133 California
- GreaseCar Veg System

I replaced all my shocks, but i did put the washer upside down. If i recall, i also took it off that way. And after the rebuild the noise happens more often so I will give it a try.

__________________
1981 300SD 512k OM603

reversing it did not help at all.

__________________
1981 300SD 512k OM603

Well it was worth a shot.

BTW - When you tightened down the shock, did you tighten it down enough for the rubber bushing is smooshed to a tad wider then the washer? Approximately > or < 40 ft lbs of torque.

__________________
1983 123.133 California
- GreaseCar Veg System

Yes, I put it to 45ftlb




Someone that has locktite on hand needs to remove their caliper and see if theres any play in the piston. This is really the only thing left that can be making the noise.

__________________
1981 300SD 512k OM603

I did check the idler arm last night and it has no apparent shake, and the bolt is very tight...I did replace this bushing kit about 18 months ago, so I would think that it is still OK. You say that sometimes it goes bad and you really can't tell, requiring only a very small amount of play to cause the symptoms I describe. On the one hand, I just want to get another rebuild kit and install it, but on the other hand, I dont want to start replacing parts I just replaced a short while ago. What I will do is take it apart and see if there is any loose fitting component that should be tight, then go from there.

Thanks a lot,

Mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

A while ago, I put my winter tires on the front (mounted on separate rims), to see if the noise was tire/wheel related...this had no effect on the noise.

When listing again to the noise, is sounds so definitely related to the wheel/hub area, I will check out the things you suggest. I already did check tightness of all bolts (rotor to hub, caliper, etc.). But your comments about the non-floating calipers and possible caliper piston knock makes me think....the advent of the noise approximately coincides with my having rebuilt the front calipers. I think what I will do is, instead of taking them apart, and essentially rebuilding them again, I will just take the dam things off the car, then drive it and see if the noise happens. In order to do this, I will see if I can find brass fittings to cap the brake lines so I would at least have rear brakes, plus emergency brakes. I don't experience any pulsing at the brake pedal.

When I rebuilt the calipers, it was the first time I ever did this, and I dont recall any excessive play or distortion...I did sand the surfaces of the pistons and calipers with very fine (1500) sand paper, and everything seemed ok. Everything went back together just fine, and brakes have been just great since. I cant think of anything else associated with front end suspension that could cause the noise...all parts have been replaced (ball joints, control arm bushings, bearings, rotors, upper control arms, etc. etc.)!

In one of my previous posts when I was brainstorming about possible causes, I did think that maybe the rebuild kit I used had a too-squishy piston seal, allowing the piston to bang around inside the caliper....all this seems like a real stretch, but I am running out of possibilities.

I will update after doing these things,

Thanks for the suggestions,

Mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

Loose calipers.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I'm in the exact same situation as the first poster. Completely rebuilt suspension, but I still get a clunk from the passenger's side on "washboard" roads, except only when it's cold outside, as in 50 degrees or less. At higher temps, the clunk can't be heard. I gave up on finding this clunk a long time ago.

__________________
1980 240d
1999 SL500

I vote for loose calipers. I had same exact problem and they were loose. Are your bolts to long perhaps?

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I admit that when I installed calipers, I did not apply thread locker to the bolts; however, when I install them, I crank down with an ordinary 3/8' socket wrench, then finish it off with a large (18" long, 1/2" drive) breaker bar. I can't imagine that the calipers are loose. That said, I am in the mode of completely re-assessing everything I have done (for the 3rd or 4th time now!!!), so, as I said in my above post, I am just going to remove the calipers, cap the brake lines and drive it to see if I have the noise. If the noise persists, I will then remove the shocks and drive it.

What amazes me is that the noise over "washboard" surface is not just a subtle rattle that is difficult to hear. The dam thing sounds like the wheel could come off! There must be an obvious simple and straightforward fix, but trying to find it is the most challenging/frustrating thing I have ever encountered with this car!

You ask if my caliper bolts are too long....are you saying that the bolt holes are "dead end" holes (not "through holes")...if that is the case, maybe I will grind off some of the ends of the bolts. I can't imagine that these fat, stubby caliper bolts could stretch that much (not like head bolts), but if the bolt holes are dead end holes, maybe there is some crud built up at the bottoms of the bolt holes. Its a long shot, but easy to check and fix if that is the problem!

Thanks,

Mark

__________________
1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I would grab the caliper and give it some good shakes.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42