W202 Knocking noise from rear when turning right

[EdGasket]

W202 1999 165K miles. When turning right on full lock I am getting knocking/thumping (not clicking) from the rear of the car and to a lesser extent the propshaft now I have patched up the centre bearing rubber. So I took it to a car park and doing tight right-hand circles it thumps and knocks all the time but no noise in straight line or left-hand circles. Advice what to look for please?

 

[EdGasket]

Has no-one else had this? It feels like the drivetrain is under extreme pressure and thumping but only when turning right and pulling away. Now as the rear wheels don't steer, the only things that can make a difference when turning are the force on each wheel (maybe something twisting ?), or the height of the wheel relative to the body (suspension problem - I checked; looks OK). I guess it could be a drive axle also under stress. Would wheel bearing make a thump?

 

[Arudge]

Has no-one else had this? It feels like the drivetrain is under extreme pressure and thumping but only when turning right and pulling away. Now as the rear wheels don't steer, the only things that can make a difference when turning are the force on each wheel (maybe something twisting ?), or the height of the wheel relative to the body (suspension problem - I checked; looks OK). I guess it could be a drive axle also under stress. Would wheel bearing make a thump?

If the wheel bearing was loose enough to thump as you describe then there's an easy test. Simply grab the top of the wheel in question and rock the car using the wheel. You will feel the thump through the wheel if the bearing is loose. Make sure your car is unlocked when you do this otherwise the alarm will sound.

 

[Arudge]

Just thinking this through.......When turning there's a fair amount of force on the shocks, anti roll bars and they're associated bushes. On a hard right, the right side will sink and the left rise. So, on a hard right, load goes on the right side and comes off the left side. Any movement in the bushes will create a thump as the load swaps side. This could be exasperated by poor rebound by the shocks. (Damping is when the shock is compressed, rebound is the speed of return to extended length) Again, a simple shock rebound test is to compress the shock in question by leaning on that wing and quickly releasing. The car should compress quickly but return slowly, and not bounce. Or, at worst case, the top shock mount has broken away.

 

[EdGasket]

Unlikely to be a wheel bearing as it was only MoT'd last month. Also unlikely to be shocks as the noise / thumping continues rhythmically with wheel rotation if i drive in a tight rh circle. My guess is a driveshaft gone bad or something loose stressing the driveshaft e.g. differential twisting. Hope to have another look on Saturday; not driving it at the moment.

 

[star]

Very common on 202’s. The steering set up allows the outside front wheel to turn in too much and makes it hop on full lock.

Oops just read rear of car!!!

 

[Arudge]

MOT should have found play in driveshaft joints as well, but could well be a driveshaft. Obviously, on a tight turn one shaft turns quicker than the other but in theory the power should still be equally distributed between the two, with the difference in speed taken up by the planetary gears within the diff. I'm at a bit of a loss here, so i'll be keen to see what you find.

 

[star]

Still think steering. Do a google search steering hops.

 

[daveenty]

Just me that's thinking diff?

 

[Arudge]

Just me that's thinking diff?

No, not at all. I also thought diff but the problem would need to lie in the planetary gears, and they don't exactly move a great deal, although they would move quicker on one turn against the other turn, depends which side the crown wheel is on, which i can't remember.

 

[Arudge]

Still think steering. Do a google search steering hops.

My W208 has being doing a lot of that on these slippery/icy roads, i know exactly how that feels and it does fit the OP's description, but he insists it's on the rear. Mines unmistakably on the front.

 

[LostKiwi]

Silly question but the wheel is correctly attached to the hub and torqued up?

 

[L John]

Unlikely to be a wheel bearing as it was only MoT'd last month. Also unlikely to be shocks as the noise / thumping continues rhythmically with wheel rotation if i drive in a tight rh circle. My guess is a driveshaft gone bad or something loose stressing the driveshaft e.g. differential twisting. Hope to have another look on Saturday; not driving it at the moment.

Rhythmically with which wheel, left or right rear?
Is it one thump or more (if so how many) with each rotation?

 

[EdGasket]

So today I had a helper with me so I could see from outside the car which side the noise was coming from. We got in the car parked at the side of the road. On pulling away it made two knocks/thumps from the rear. Drove down to the same testing ground - not well used car park - where car had been making consistent knocking last Monday everytime I made rh turns, and would you 'Adam & Eve' it, the car performed perfectly. I did stops/starts tight rh and lh circles and then the same without the passenger in case the weight distribution had done something but no untoward noises at all! I'm at a loss. When it makes the noise I feel like I shouldn't be driving it and indeed haven't all week but today, apart from pulling away from cold, its perfect.

Only thing I can think of is to carry on using it until it gets much worse. Maybe its some loose bolt(s) and the diff or subframe shifting, or the drive axle settling in a certain position. Any ideas why this is intermittent as far as rh turns go, and is always the worst after being parked up and pulling away but OK once up and running and pulling away?

 

[LostKiwi]

It may be the shoes on the parking brake. The friction linings have been known to detach from the metal supports.

 

[EdGasket]

I checked all the diff bolts this afternoon and they are tight and the diff is secure; no movement if I jack up the diff a little. Think I'd get more problems if it were the brake linings but its a possibility though seems to work fine.

 

[EdGasket]

Have used it for a couple of days (about 100 miles) with no more knocks.

 

[Arudge]

Have used it for a couple of days (about 100 miles) with no more knocks.

Welcome to Mercedes.

 

[LostKiwi]

Welcome to Mercedes.

I always thought that was Land Rovers....

When it stops making a noise it just means its fallen off!

 

[mikestrivens]

Mercedes are self repairing as even they get fed up with the rip off dealer prices.