noise going up hills - PeachParts Mercedes-Benz Forum

Jack None · #1 07-17-2017, 03:31 PM

I have an '84 300D. Recently it started making a very clear, speed-dependent fwap fwap fwap noise but only when going up steep hills, which sounds like it's coming from the rear under the car.

Any ideas?

renaissanceman · #2 07-17-2017, 03:34 PM

How are the flex discs?

Dmitry at Pelican Parts · #3 07-17-2017, 08:13 PM

+1 on the flex discs - in case they need to be replaced, take a look at the DIY tech article from our site on the procedure. Please let us know if you have any questions!

Mercedes-Benz W123 Flex Disk Replacement | W123 (1977-1985) | Pelican Parts DIY Maintenance Article

t walgamuth · #4 07-17-2017, 09:01 PM

CV joints maybe too.

Jack None · #5 07-18-2017, 11:02 PM

Thanks. Flex discs both look pristine (PO must have had the work done, Mercedes parts, too).

Bearing mount near universal joint looks like it may be original, though. It is coming apart.

But I suspect it's the CV joint on the right axle close to the gear box. It is a Chinese replacement that Kent sold me about 2 years ago. Good thing I kept the original which I will rebuild (I rebuilt the one on the left side, because I had to send the Chinese one back since the shaft diameter was out of spec). The Chinese one rusted after a few months, and now the rubber boot is already ripped and spraying grease around.

Jack None · #6 07-18-2017, 11:14 PM

Has anyone heard of failing CV joints making whomp whomp sounds but only going up a steep hill?

barry12345 · #7 07-19-2017, 11:50 AM

The physical loading on the cv joints is of course heavier when going up steep hills. Not a usual complaint but a possible cause of what you hear. Many seem to be okay with buying Chinese axle replacements. I am just not a fan of them myself.

Your center bearing sounds like it needs dealt with anyways. So perhaps do it first as it might be the cause.

Clemson88 · #8 07-19-2017, 02:19 PM

Quote:

Originally Posted by Jack None

Thanks. Flex discs both look pristine (PO must have had the work done, Mercedes parts, too).

Bearing mount near universal joint looks like it may be original, though. It is coming apart.

But I suspect it's the CV joint on the right axle close to the gear box. It is a Chinese replacement that Kent sold me about 2 years ago. Good thing I kept the original which I will rebuild (I rebuilt the one on the left side, because I had to send the Chinese one back since the shaft diameter was out of spec). The Chinese one rusted after a few months, and now the rubber boot is already ripped and spraying grease around.

I'd say if the carrier bearing housing is allowing the bearing to flop around you probably should replace that housing first. It seems an bad axle would pop when going from forward to reverse or vica versa. I don't know though I've never had one to go bad.

Jack None · #9 07-19-2017, 08:49 PM

Thanks. The carrier bearing mount is definitely bad so it makes sense to replace first.

Is there a way to test the CV joints while still in car, maybe check for play in the joint?

Diseasel300 · #10 07-19-2017, 09:13 PM

Check for oil or grease being slung out of the CV boots. If they're dry, they're probably still ok. Generally as long as the grease/oil hasn't been leaked out, they'll last a very, very long time.

Clemson88 · #11 07-20-2017, 06:33 AM

Quote:

Originally Posted by Jack None

Thanks. The carrier bearing mount is definitely bad so it makes sense to replace first.

Is there a way to test the CV joints while still in car, maybe check for play in the joint?

Without experience in evaluating CV axles I can only tell you what I've read about evaluating them.

I have heard that if the axle fails completely the car won't move under its own power. A bad joint can usually only be diagnosed with the axle out of the car. The extra rotational movement is often disguised as movement in other components such as the differential.

Imo, this has nothing to do with your problem. I believe the flap, flap, flap is the late stages of your carrier bearing housing failure. Be warned, study the DYIs carefully along with the Factory Service Manual before you start this process.

I'd plan to buy factory parts from the dealership and replace the bearing along with the bolts on the flexdisk. I would replace the flexdisk but I can't say that's what you should do.

I feel this way about the flex disk because I do not believe anyone who would use a factory MB flex disk would ignore a faulty carrier bearing housing. Those disk are a lot older than they appear, imo. Never-the-less, when you remove the drive shafts you can take a much better look at the disk.

vstech · #12 07-20-2017, 07:58 AM

Where does the noise feel to be originating? Center, rear? Left right?

Perhaps sway at links?

It's only climbing hills... never on a sharp left or right curve?

Jack None · #13 07-21-2017, 06:57 PM

Yes, only climbing hills. Never on a turn. I can't pinpoint the noise that well. Definitely from the back half of the car.

There's more than half an inch of play in that drive shaft near the carrier though and I can visibly see that the mount isn't doing its job, so it's not a stretch of imagination that it might fwap its way up a hill.

I am not worried about the flex discs, for this reason: the PO did not do her own work on the car, and I suspect she had the flex discs replaced b/c a mechanic told her she was close to catastrophic failure (would have been at 290k miles). The carrier bearing would have been an extra $500 after parts and labor and she was gearing up to sell. Also, I've replaced a lot of old rubber parts on this car, too many to remember, and the discs look extremely good.

I will replace carrier bearing & mount and report back about the noise.

These old cars, anyone count how many rubber parts total? I figure at some point I'll have replaced every single one.