thumping / knocking noise

[conleycrew3]

hi all,
i have just developed a new noise, a loud knocking / deep thumping from the rear passenger side wheel area i think.

its only audable in the car, not from the outside, and its when i set off up to 20mph ish then goes. its not there at ay speed over that.

if i get to the speed that the noise occours then put it in N the noise goes, but i have only done that once so i could be wrong.

i have reversed and there is no noise at whatever speed i go.

i have 'hammered' the gas pedal in D and 2 and 3 separatly and the noise is still there but only up to 20mph or so.

there has been no build up to this happening, the noise has just appeared out of nowhere??!!

i had pulled over to empty some rubbish into a bin, got back in the car, and pulled away calmly, and then it started!?????????

any ideas people?
cheers
Ben

oh yeah, its a 1988 300ce

 

[grober]

Have you done a detailed visual inspection under the car?
Could be any or none of the following.
1. defective tyre
2. torn universal joint boot on drive shaft
3. soft differential mounts
4.propshaft flexible coupling.
5.broken exhaust mounting.
6. loose wheel bolts
7.broken handbrake shoes/springs
8.defective rear subframe mounts

 

[conleycrew3]

1. defective tyre
2. torn universal joint boot on drive shaft
3. soft differential mounts
4.propshaft flexible coupling.
5.broken exhaust mounting.
6. loose wheel bolts
7.broken handbrake shoes/springs
8.defective rear subframe mounts

well numbers 1, 2, 4, 5, 6, are ok so thanks for the heads up i will have a look in the light tomorrow thanks

i would take her to the garage but its friggin bank holiday!!

do you think its un safe to drive? i mean the sound is only at a certain speed and doesnt get any louder more so it goes when i go faster??

i love driving and i drive her every day without fail so i will be devastated if i cant take her for a cruise

 

[grober]

Any unexplained mechanical noise should be investgated ASAP. Until you know what it is you cant assess the risk so my advice would be err on the side of caution. Sorry.
edit;- I've just thought of
9. broken antiroll bar link
10. broken antiroll bar mounting or bush
11. damaged rear suspension bushes/links
12 broken/corroded rear spring.
my money would be on 7.

 

[conleycrew3]

number 7 would make sense i supose as i have to push the pedal to the floor and then some before it engages, even then, id be lucky if it stopped me rolling at a trafic light on a flat straight road whilst in D!!!

i really hope it is the handbrake shoes because them bush links etc are pretty expensive!

i hate having problems like this, having said that, this IS THE ONLY PROBLEM IV HAD SO FAR!!!!!!!!!! so i guess i cant complain!

iv had other noises before from various places in the car but they have cured themselves after a day or two but this is the most serious weird worrying noise so far because it happens when im moving no matter how hard or gentley i accelerate.

i have her booked in for her MOT on tuesday so i hope they find out what it is without taking the p**s saying its worse than it actually is!!

 

[conleycrew3]

what about my u joint?

would that ddo it?

 

[pineer35]

Hi Ben its the hand break shoes that are worn,or fragmantated, thats causing your knocking problem.
Cheers Eddie

 

[conleycrew3]

thanks for that.

next question about the problem.....

on another merc forum they all seem to think its my u joint (dunno what that is to be honest but its something to do with the prop shaft i think??!)

could it be the u joint do you think or shall i stick to the handbrake shoe theory?

again, many many thanks for your help!
cheers
Ben

 

[Dieselman]

They/You mean CV joint.
I think it could well be a CV joint, they are the joints in the driveshafts to each wheel.
You might notice a difference in the speed of the noise when turning full lock left then right at a set speed.

Probably pulling back the gaiter and repacking with molybdenum grease will produce a fix.