My 1983 300CD started to make a humming sound. It is constant and "all the time" It is speed dependant, where the pitch changes with the vehicle speed, but not the engine speed. It is clearly audible, but not overwhelming, almost like I have noisy offroad tires on it. I think it may be comming from the front of the vehicle, and may be a wheel bearing? Otherwise the rear, where it could also be a wheel bearing, or driveshaft issue? Or maybe I am off base entirely.

What do you think?
What is it?
Is this something I can fix in my backyard with ordinary tools?

Mark

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1983 300CD 245K
Running WVO blends

Most likely a wheel bearing. You can fix in you backyard. You can usually get by with simply repacking the current ones, but they are cheap, so ou may want to just replace them on principle. You'll need grease, channel locks, allen key (can't remember what size, 10mm?), and a drift and hammer if the races little "cups"that press into the hub and fit against the bearings) are scored and need replaced. They made my car sound like they were riding on really knobby tires.

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1989 300E 144K

Have you made any changes to the running gear recently?

Does the sound change in long sweeping turns?

First, you need to identify where the sound is coming from (front vs rear, right vs left).

My first guess (assuming you haven't gotten new tires or something else) would be a front wheel bearing.

Also, before getting into the bearing job, isolate the quarter the noise is coming from, and rotate another tire to it, just to make sure that radial noise isn't at fault here.

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1989 300E 144K

This started happening about 2-3 months after getting a couple of ball joints, and the pittman arm? replaced and aligned.

Havent done anything recently with the tires.

Is it serious, or can I put it off for a couple of weeks?


Wierd thing is, it is so constant, and not just if I am making a certain kind of turn, left or right.


Mark

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1983 300CD 245K
Running WVO blends

You need to figure out exactly what it is to know how serious it is, I agree it's likely a bearing, and I've seen bad bearings go months that way, and also have seen them lock up and destroy spindles the next day. (not to mention what it does to the driver's nerves trying to control the car). If you suspect the front, try jacking each front wheel up off the ground, grasp it at 6:00 and 12:00 (top and bottom) and try to wiggle it. It should be tight, if it has slop, or you can feel a little clunking sensation, it needs to be checked. Also roll the tire by hand and feel for any roughness. I believe you can also check the rears this way too, since these cars use IRS suspension. When checking bearings, any scoring or discoloration means replace them. If they are still smooth without any coloring you can repack them and reassemble them to proper preload. If you dont find anything doing that, look over your flex disks and center support on the driveline, any cracks in the disks, and a lot of loose sloppiness in the support are no-goodniks.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale

I called my local auto parts store. He said he had the front wheel bearings, but asked me if the spindle was 50mm, and I was like: I don't know...

Mark

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1983 300CD 245K
Running WVO blends

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When I changed out my wheel bearings, it was at Auto Zoo, using Timken. Thier part numbers were set3 and set5. I do not recall which is which. My car did the same thing, noise and that was it. Finally I raised up the front end because it got louder. All that time I figured is was road noise from the chip seal type paving they like to do. Turned out is was the driver side inner bearing. There was no side to side play, but I could feel the bearing "clocking" when I spun the wheel slowly. The race had a low spot that was not polished. It was a poor casting.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D