cyclic knock when braking

B-Hive · Post by **B-Hive** » Thu Aug 04, 2011 8:45 am

Hello

With the GT now my daily driver (and loving it),its time to sort out and refine things as I experience new issues.

My issue at the moment is that under average braking I get a distinct cyclic knock that disappears as you slow to about 15kmh to stop. I havent been game to test this problem under heavy braking incase something goes snap,, so am keen to diagnose early..

"Seems" to be coming from left hand front but quite hard to tell. My first thought was left engine mount as I think it is tired but why would it be cyclical..I would have thought it would produce a single clunk on braking then maybe another on take off.

It doesnt sound/feel like warped brake discs but perhaps, if they are out of true, combined with another worn part it may be emphasising a weak drop link or something else... or even oscillating the bad engine mount to and fro??

Could it be in the hub, or maybe the outter joint...

I did notice when I took off the central gearbox guard/and pipe mount frame (to access the accumulator),, that there has been interference between the gearbox and this guard..

So yes I will be replacing the left engine mount,, but I'm not convinced that this will cure this knocking under brakes

Lotsa options...

Any wisdom???

rmattila · Post by **rmattila** » Thu Aug 04, 2011 9:38 am

2BXORNOT2BX wrote:My first thought was left engine mount as I think it is tired but why would it be cyclical..I would have thought it would produce a single clunk on braking then maybe another on take off.

Loose engine mounting can lead to the inner driveshaft joints hitting the surroundings, producing three clunks per turn.

(Such as those.

)

Jaba · Post by **Jaba** » Thu Aug 04, 2011 5:29 pm

A disc that has worn thin will eventually develop visible radial cracks which produce the sort of noise you describe.

MULLEY · Post by **MULLEY** » Thu Aug 04, 2011 7:04 pm

My money is on a warped disc, as the speed lessens the effect of the warp is diminished & hence it appears to get better & disappears.

B-Hive · Post by **B-Hive** » Sat Aug 06, 2011 6:40 am

Thanks guys...

Not sure if its my imagination but it seems to be worse if you are steering right whilst braking

Any how I'll have a look at the discs when it stops raining...do the discs fail/shatter because of these hairline cracks?

Way2go · Post by **Way2go** » Sat Aug 06, 2011 6:03 pm

2BXORNOT2BX wrote: Not sure if its my imagination but it seems to be worse if you are steering right whilst braking

Sounds like more of a disintegrating CV joint problem than discs.

rmattila · Post by **rmattila** » Sat Aug 06, 2011 6:33 pm

Way2go wrote:Sounds like more of a disintegrating CV joint problem than discs.

It would, if it happened when accelerating, but as it happens during braking, it's more difficult to connect it to CV problems.

MULLEY · Post by **MULLEY** » Sat Aug 06, 2011 10:34 pm

What about a wheel bearing? If the noise always happens whilst turning right that might possibly be it.

scarecrow · Post by **scarecrow** » Sun Aug 07, 2011 9:57 am

I drove a transit minibus from Maidstone to Stansted with a strange regular knocking - turned out I'd pressure-washed in the wheel-arches and dislodged some mud trapped behind the wheel (which must have been on the spare which got put on after a puncture) thereby loosening the wheel a little and eventually squaring of the bolt holes on that wheel. Made one hell of a racket by the time I persuaded the farmer that it should go to the garage

Irony was one of my passengers was a traffic cop

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cyclic knock when braking

cyclic knock when braking

Re: cyclic knock when braking