C230WAK

I have a 2005 C230 with over 270,000 miles. The engine runs great except for the occasional P0420 code. However I have a buzzing/humming sound coming from somewhere whenever I get up to around 35 mph.


I thought is was the front wheel bearings because whenever turn left on the highway to go around a left hand curve, the sound goes away. The sound is always there when I go straight or turn right. But I changed both the front wheel bearings and the sound is still there. Then I thought it was possibly because the front tires were worn on the inside so I changed the tires, the control arms, the tie rods and got a wheel alignment and the sound is still there.


I'm convinced now that the sound is coming from the rear. One of my many questions is, would the sound from a bad REAR wheel bearing go away when I change direction? And is a rear wheel bearing a DIY job? I also read somewhere that someone was getting a buzzing sound from the rear differential.
Any help or hint would be appreciated.

Preet

i would guess the rear diff

LexBrett2

The sound could literally be anything. The only way to diagnose is to get under the car. It could be something really obvious like a loose heat shield. If you take it to a mechanic and just say you hear a noise might as well give him a blank check

C230WAK

Does anyone know if the noise from a bad REAR wheel bearing would change if the car swerves or turns? The from my car completely goes away if I swerve or turn the car to the left.

Russell Ormerod

check the left rear wheel bearing. if you turn left it will unload the left wheel yes.

C230WAK

I checked the left rear wheel and it is solid with no play at all. I wonder if it could still be cause of the noise.

Russell Ormerod

and if you rotate it. does the bearing feel smooth as silk

C230WAK

There is no play in the wheel. It feels ok when I rotate it. I got the rear end on jack stands so that the rear wheels are off the ground, I put the car in Dyno mode and then put the car in drive. I didn't hear the humming sound with the rear wheels off the ground. I heard an intermittent scraping or scratching sound but it seem to be coming from both sides. I'm assuming that is just the rotors.
Also I'm assuming that I didn't hear anything because there was no pressure on the bearings. I don't know.

Russell Ormerod

I meant rotate it by hand to feel

C230WAK

You were correct. It was the left rear wheel bearing. I took off the knuckle with the hub attached and when I spun the hub, it sounded horrible. I bought a used knuckle, with the hub attached, from a salvage yard and now my car is back to being quiet. I had to change the bushing on the used knuckle but that was surprisingly easy with the Sir Tools M0085 tool. Thank you for your help.

RWDlifer

A brand new bearing is about 50 bux, why are you going with a used one that might go out a few months down the road? When I did mine I got the 2 bearings for less than 100 bux shipped, removed both rear hubs and took them to a machine shop to get the bearings pressed, cost 50 ish bux. So for about 150 bux I have new bearings (also did the knuckle bushings) that I don't have to worry about.
Plus, if one bearing went out, the other side is close behind.

C230WAK

I got the used knuckle for $40 and I felt lazy. lol But I will replace the bearing in the knuckle that I took off the car. I just wanted a quick fix because I wasn't sure that was the only thing causing that racket. But you are definitely correct replacing it with a brand new bearing would have been the best option.