Weird noise - PeachParts Mercedes-Benz Forum

mattwestm · #1 11-18-2014, 07:57 PM

I posted this on Benzworld, but thought I might get some different opinions here.

I've been getting a weird noise from the driver rear of my car. It starts once I hit 10mph and seems to match the engine speed. If I'm driving 30mph with the gas down, I hear "tick tick tick tick". The more I press the gas, the faster it get and if I release the gas, the sound goes away immediately. When the weather is warmer, it seems quieter and as the car warms up it seems quieter.

Was thinking that something was making contact, but considering the sound goes away when I release the gas, I'm not convinced. Could it be the exhaust?

I noticed this today (see picture). Is there supposed to be some sort of rubber or bolt here? Also, how many rubber exhaust donuts does the 300SD have? I'm only seeing two towards the end of the exhaust pipe.

barry12345 · #2 11-19-2014, 12:37 AM

The outer cv joints may need lubricant added even if the boots appear dry. A syringe and small hose can let you add some with the inboard boot clamp off. A very heavy oil is best.

This is not an absolute solution but something that perhaps should be done anyways on these very old mercedes cars.

Plus the first symptom of an ultimately bad cv joint on these cars can be an intermitent click click sound. Catch it early enough and all will be well.

A problem on that side as actually the slight discoloration on the axle shaft looks like some lubricant may have been lost there over the years. The original joints where oil lubricated rather than grease.

Oil is better and if what I suggest cures the problem on that side do the other side as well as a preventative thing. Drive on it too long and you will seriously damage the joint. Fortunatly the design seems to give advanced notice of being pretty dry on these cars. Yours is talking to you now I really suspect. Also look to make sure the boot is still intact. A little oil creeping out the end of the boot over time is in itself not an indicator the boot is bad

t walgamuth · #3 11-19-2014, 06:28 AM

Quote:

Originally Posted by barry12345

The outer cv joints may need lubricant added even if the boots appear dry. A syringe and small hose can let you add some with the inboard boot clamp off. A very heavy oil is best.

This is not an absolute solution but something that perhaps should be done anyways on these very old mercedes cars.

Plus the first symptom of an ultimately bad cv joint on these cars can be an intermitent click click sound. Catch it early enough and all will be well.

A problem on that side as actually the slight discoloration on the axle shaft looks like some lubricant may have been lost there over the years. The original joints where oil lubricated rather than grease.

Oil is better and if what I suggest cures the problem on that side do the other side as well as a preventative thing. Drive on it too long and you will seriously damage the joint. Fortunatly the design seems to give advanced notice of being pretty dry on these cars. Yours is talking to you now I really suspect. Also look to make sure the boot is still intact. A little oil creeping out the end of the boot over time is in itself not an indicator the boot is bad

All true.

mattwestm · #4 11-19-2014, 11:35 AM

Thanks for the reply barry. What kind of oil should I use? When injecting the oil, I should insert it from the smaller side of the boot, correct? It looks like that clamp has a screw to loosen it.

The only thing I'm concerned about is the fact that the noise dissipates when I release the gas. Wouldn't a CV boot make the same noise at all times, only increasing in noise when the car goes faster?

barry12345 · #5 11-19-2014, 02:12 PM

Quote:

Originally Posted by mattwestm

Thanks for the reply barry. What kind of oil should I use? When injecting the oil, I should insert it from the smaller side of the boot, correct? It looks like that clamp has a screw to loosen it.

The only thing I'm concerned about is the fact that the noise dissipates when I release the gas. Wouldn't a CV boot make the same noise at all times, only increasing in noise when the car goes faster?

Changing loading on the balls etc in the cv joint changed the noise was already a clue. Just add some heavy oil. You have the technique right.

Certainly it may be something else. Yet this would be my first suspicion it is the problem with your description. Two to four ounces of seventy five to ninety weight oil inserted should tell.

Make the tube on the syringe as small as practical. Perhaps enough tubing to attempt to get the oil in further as well will not hurt. You do not want to stretch the old boot more than is required to slide the the tube in.

I also suspect the original clamp was a compression type rather than a screw clamp. So whatever the reason someone has done something before. I could be wrong about that though.

A more typical indication is when taking a 123 on a road trip. With inadequate lubrication after enough miles are run the cv joint gets hot and clicks. Basically all that will usually be required is to get some new lubricant in there before so much damage is caused the joint is finished. I do this after acquiring an old 123 and going into service to avoid the issue occurring down the road. Even though there is no click in evidence. Really for me it is just preventative maintenance.

Affordable new axles are poor in comparison to the originals. Good new original axles are really expensive. Used ones from a wrecker rebooted and relubed are a better bet than the cheap Chinese axles. Few of these cars are scrapped because of bad axles. Also by putting used axels on the opposite side when installing them on our cars gets a new wear area going in the cv joint itself. They are interchangeable side to side.

As long as the noise is not continuous you usually have caught the problem early enough. Again there is no way I can be absolutely positive about this post. It is just the best guess I have about your issue.

Takes little real effort to do as well. A large drugstore syringe and a piece of tubing plus some oil gets you into business. Even if I am wrong the rear outer joints should receive some new additional lubricant after thirty years.

Old boots are tricky and new fairly hard to install so this is a reasonable compromise. The proper way to do something like this is to remove a boot. Flush the cv joint out. Apply the right amount of oil with a new boot. You have to remove the axle though to do this. The compromise instead should be fine. It is a lot easier as well.