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1984 Mercedes-Benz 300DT; 1980 Mercedes-Benz 300SD
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Discussion Starter #1
Ok, well, the noise has come and gone, sometimes I wont hear it for weeks, or longer, but then I hear it for days...

It seems to originate on the drivers side rear tire, the car doesn't seem to be affected by it, besides the noise, accelerated/brakes without a problem, I took the tire off, and CV boots were in intact, dont know what else to look for, I've made a small audio file with my cell phone, so please bear with me, you'll have to listen to the entire 44 seconds of audio:

zSHARE - audio002.wav


If anyone can give me any info on what it could be, I'd greatly appreciate it.


torkq
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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Sounds horrible, did you record this from the drivers seat?
Rear wheel bearing, maybe?
Pull the hub, and inspect the parking brake, sorry, but that's all I've got.
Good luck.
 

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1985 300CD
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I agree with the wheel bearings being a possibility. Jack the wheel up and see if you can feel any wobble or hear anything.

Rear wheel bearings are one job I'd pay someone to do.:eek:
 

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I have a similar problem.

My 240Ds rear half axles are going bad. From a post either here or at mercedesshop.com, someone pointed out the the half axles form a wear pattern from primary forward motion. If you drive in reverse for a short distance, some "resets" and you can get a few more miles before the noise reappears. SO I tried it, it worked for me.

I know the half axles need to be replaced, but this gives me a few months or more to do some other more pressing maintenance - oil cooler lines, aux cooling fan.
 

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money pits of various forms
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God that sounds awful. I would go with the easy fix first and replace the axle. Just find a decent looking one at a yard, its a pretty easy fix and a $30 or so part used. Bearing is PITA.
 

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1984 Mercedes-Benz 300DT; 1980 Mercedes-Benz 300SD
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Discussion Starter #6
Sounds horrible, did you record this from the drivers seat?
Rear wheel bearing, maybe?
Pull the hub, and inspect the parking brake, sorry, but that's all I've got.
Good luck.

Yes, while driving, I went to a quiet part of town, and was trying to accelerate so I could give the listener the full aspect of the clank, I was finally able to get the rear drivers side window working, so being able to hear this even worse, was my prize...
 

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1984 Mercedes-Benz 300DT; 1980 Mercedes-Benz 300SD
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Discussion Starter #7
I have a similar problem.

My 240Ds rear half axles are going bad. From a post either here or at mercedesshop.com, someone pointed out the the half axles form a wear pattern from primary forward motion. If you drive in reverse for a short distance, some "resets" and you can get a few more miles before the noise reappears. SO I tried it, it worked for me.

I know the half axles need to be replaced, but this gives me a few months or more to do some other more pressing maintenance - oil cooler lines, aux cooling fan.

triguy84, when in reverse, I hear the noise 95% of the time, but of course since its in slower speeds, its just a clank here and there, but definately clanks, lol, and it doesn't seem to help my forward motion, I wont hear anything for a while, then I'll hit a bump or whatever and hear it all over again, good luck on the oil cooler lines, I did my aux fan a while back, and it was cinch.
 

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that's awful. How fast do you have to go before you can hear this? it sounds like a piece of the parking brake broke off inside or your rear dif is completely shot. anyway, if you put the car on the lift and let it run it shouldn't be hard to locate. good luck
 

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1984 Mercedes-Benz 300DT; 1980 Mercedes-Benz 300SD
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Discussion Starter #9
I agree with the wheel bearings being a possibility. Jack the wheel up and see if you can feel any wobble or hear anything.

Rear wheel bearings are one job I'd pay someone to do.:eek:


winmutt said:
God that sounds awful. I would go with the easy fix first and replace the axle. Just find a decent looking one at a yard, its a pretty easy fix and a $30 or so part used. Bearing is PITA.

I jacked up the car yesterday, and I couldn't find a thing wrong with it, I thought I was going to see atleast the hub setup as the front wheels, Im thinking I would have to remove the entire caliper and rotor??

I just found a mpeg video I had purchased when I first purchased the car on brakes, and it has a nice tutorial on rotors, pads, and repacking the front bearing(s), the guy switches over to the rear pads/rotors, and doesn't say how to repack them, just says "the rear ones are easier"..... :(
 

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Discussion Starter #10
that's awful. How fast do you have to go before you can hear this? it sounds like a piece of the parking brake broke off inside or your rear dif is completely shot. anyway, if you put the car on the lift and let it run it shouldn't be hard to locate. good luck

Sometimes as soon as I pull out, sometimes I go weeks, or longer without even hearing a little clink, but you know, funny that you should mention it, I've seen that lately when I do apply the parking brake, it only seemed to "grasp" on one side, I can even feel the car move in a certain direction, I have absolutley no access to any lifts, and any local shop would surely charge me hundreds of $$$ to even diagnose the problem, atleast thats how they act around here (Los Angeles)
 

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I jacked up the car yesterday, and I couldn't find a thing wrong with it, I thought I was going to see atleast the hub setup as the front wheels, Im thinking I would have to remove the entire caliper and rotor??

I just found a mpeg video I had purchased when I first purchased the car on brakes, and it has a nice tutorial on rotors, pads, and repacking the front bearing(s), the guy switches over to the rear pads/rotors, and doesn't say how to repack them, just says "the rear ones are easier"..... :(
Replacing the rear rotors is easier because you don't have to deal with the wheel bearings like you do for the front rotors. The rear wheel bearings require multiple special tools and you definitely want to use a gauge for seating new wheel bearings squarely.
 

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Discussion Starter #12
Replacing the rear rotors is easier because you don't have to deal with the wheel bearings like you do for the front rotors. The rear wheel bearings require multiple special tools and you definitely want to use a gauge for seating new wheel bearings squarely.

Is there a shopping list of special tools, or is this something I definately should leave to a shop?

I like to stray away from shops until I know exactly whats wrong, since they'll say "this is whats its causing the problem", go ahead with the repair, noise continues, then say it might be something else...
 

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Is there a shopping list of special tools, or is this something I definately should leave to a shop?

I like to stray away from shops until I know exactly whats wrong, since they'll say "this is whats its causing the problem", go ahead with the repair, noise continues, then say it might be something else...
The instructions and list of tools are in this link:

Replacing the rear wheel bearings on a W123, W126
 

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Discussion Starter #14
Thanks,


Just got off with a local (highly praised) mechanic, told me to bring it in tomorrow morning, I tried to explain to him my observations, and he ruled out axles for the moment, saying I should only hear something after an extensive amount of driving, and about the bearings, that I would always hear something, not off and on like I do, so he said its probably the sway bar link? I told him I would first only hear it with a large load (2+ rear passengers, or a good amount of weight in the trunk, or both).

Anyone know if this could be the problem, before I look like a noob that wont even change his own oil tomorrow?


torkq
 

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1985 300CD
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It could be the problem if the rattle comes when going over rough roads.

You can check the sway bar links yourself. They need replacing if they are completely broken or if the rubber boots are torn at all.

They only cost about $12 each and take about 20 minutes to replace both. They are easier to replace with the rear wheels off.

Here's a pic of one of my new sway bar links installed. I took this pic before I put the second "locking" nut on. My old ones had tears in all the rubber boots and had no grease left in the sockets.

 

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1984 Mercedes-Benz 300DT; 1980 Mercedes-Benz 300SD
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Discussion Starter #16 (Edited)
Thanks chad300tdt, is the sway bar link the "white" bar in this picture? And if so, is it just two bolts/nuts holding it in place?

Amazingly enough though its now RAINING here in Los Angeles, thanks global warming....
 

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Yup ... it's the white bar.

The bottom of the bar screws into a threaded hole and doesn't use any nuts. The top of the bar connects to the end of the sway bar with 2 nuts. The second nut acts as a locking nut. My pic only shows the first nut threaded on.


Here's a link that shows how they look before installation and they are cheaper than I remembered.

https://www.autohausaz.com/search/product.aspx?sid=dmrxbarjetbttkyonwsrti55&[email protected]&[email protected] &year=1985&cid=sway bar [email protected] bar link&[email protected]/Sway Bar Link
 

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Discussion Starter #18
Finally stopped raining, and I was able to check it out, seems the sway bar links are intact, and amazingly, the ONLY white thing under the car, I took the caliper and rotor off to see if any of the parking brake was maybe hanging in the way, and nothing, dont know what else it could be....
 

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The only other possibility that wasn't mentioned is subframe bushings or the bushings on the sway bar itself. But again, they would be when the car is driving over roads that would make the worn parts bump. I don't think it would make a noise on a smooth, bump-free road and wouldn't sound rhythmic unless you're driving over expansion joints in the road.:confused:
 

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Discussion Starter #20 (Edited)
Nope, but like I said, it comes and goes, and comes back when I hit a good bump in the road, or have a good load in the back, could the noise be coming from the rear shocks??
 
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