Transmission Noise (?)

[Bestbear]

My "new" Citroen XM prestige is a very pleasing buy, but it has one problem I am unsure about: It makes a rythmical noise between 40 mph and 60 mph. It is hard to describe noises, but it sounds a little like the "whiffling sound" you get if a wheel bearing is on the blink. "Yah-yah-yah-yah ...."

It vanishes on the over-run, and is louder when the loud pedal is pressed ...

Any ideas?

This post has been edited by Bestbear on October 23, 2005 03:57 pm

[Peter.N.]

It most likely is a front wheen bearing. Try cornering fairly hard when the noise is there, if its a bearing it will get louder when more weight is on it i.e. if you corner right the weight will be thrown onto the left wheel. Taking the weight off may cause the noise to completely dissapear. My n/s one is noisey and I have allready bought a bearing for it but as it hasn't got any worse in the last 10k, I havn't fitted it.

Peter.N.

[noz]

Hi bestbear,

Can you tell if the frequency of the yah-yah is related to road speed or engine speed? ie for the same road speed, does the frequency go up if you change down a gear?

The disappearance on overrun suggests CV joint or engine related.

If CV joint then find a big clear car park. Stop. Engage first gear and turn the wheel as far as it will go in one direction. Drive around in circles with the loud pedal pressed. Repeat in the opposite direction. The noise difference should tell you which one has gone. The loudest will be the outside wheel when turning. ie clockwise - nearside, anticlockwise - offside.

The engine noise could be related to engine mountings or exhaust. When pressing harder on the loud pedal the engine rocks further on the engine mountings. If a part of the engine is touching the chassis then the engine vibration will be transmitted through to the bodywork. Of course on overrun, the engine rocks back to its original forward position and further away from the chassis so the noise goes away. The same goes for the exhaust. It may be clear of the body when you look at it on the ramps but when the engine is loaded and rocks backwards then it might be enough for the exhaust to touch the chassis. Check for adequate clearance all around the exhaust and in particular the condition of the rubber mountings on the first box, they're prone to perishing.

Hope this helps.

Cheers

noz

[Bestbear]

Thanks for these helpful suggestions. I'll try them all and report back!