Clunking Brakes

[mof]

Slowly reverse and then apply the foot brake. A 'clunk' noise and the brake pedal pushes back up at me.

Car still stops fine and dandy.

I strongly suspect perhaps a 'mounting' problem on transmission somewhere, rather than the brake fluid being forced back up the pipes and pushing the pedal back at me!!

After all, the brake pedal pivots on the same rod as the clutch pedal. Could clutch linkages be transferring some movement to the brake pedal shaft?

Look underneath the rear axle and find the 'ball joint' which links the rear nearside damper arm to the rod which drops down from the rear chassis rail has seperated. The rubber in the ball joint has perished and the ball is no longer held in the socket.

Could this all be part of the same problem?

Merry Christmas!

[Willie]

Well,yes! at the very least it means that you have no damping
onn that side of the car. The links are available separately,
replace both,not one, and check that the mounting bolts are
tight on the dampers. If that doesn't cure your clunk then we
can take it further.................The clutch and brake pedals
can seize due to lack of lubrication, If you operate one of them
and the other pedal goes down with it than you need to free
then and oil, preferably with EP90 rear axle oil.

[Chris Morley]

The cluch and brake pedals are mounted on the same shaft and they can both move if the lubrication has dried out, so the clutch linkage & brake pedal theory sounds feasible. However I can't see how a worn rear damper can have any bearing on the brake pedal pushing up.

Did the pedal push up once, or is this something which can be replicated every time you reverse?

[mof]

Yes, this clunk happens just about 99% of the time when reversing. It is possible to prevent it, but only by really really gentle braking. The car has always had some shocking juddering when reversing, which has to be avoided by slipping the clutch a lot.

Perhaps the rear damper issue is a red herring, but I was pretty sure we were looking more at a driveshaft/suspension/mounting issue rather than brakes.

Yes indeed the brake and clutch share the same shaft

I wonder if the transmission shifts when braking in reverse and the effect is transmitted up the clutch linkages some how?

It seems more likely that the fluid being pushed back up the hoses. I'm not even sure if its possible to force the pedal back in that manner anyway.

I hate mysteries!

[Chris Morley]

It's a mystery alright....

The judder in reverse has several possible causes (the worst case being a warped or badly worn clutch plate). More likely however is 1) the gearbox steady is either broken or too slack, 2) A broken engine steady. The gearbox steady prevents the engine/gearbox moving lengthways, the engine steady (should) reduce lateral movement. Condition of the engine & gearbox mounting rubbers can also have an effect on excessive movement.

This is a pure guess, but perhaps if some of these items are loose or worn, any sudden braking while going backwards might cause the combined engine/gearbox to 'clunk' against something because they continue to move backwards momentarily after the car stops ? This might also explain the pressure applied to the gearbox linkages which moves the pedals?

[rayofleamington]

How much free play is there in the clutch pedal?
There should be lots for a number of reasons
One reason is that the engine/gearbox will move slighly under braking.
The pedal shaft may have some clearance with its bearings which could make the brake pedal move if the clutch linkages put load back to the clutch pedal / shaft.

[grainger]

hi

have you recently changed the brake pads ? ... could be loose or the wrong way round ?

cheers
grainger

[Gareth]

I had the brake and clutch assembly shaft reconditioned a while ago. Before this, when I put the clutch pedal down and released it, it would only release about 4/5 of the way. To get it up for that last fraction I either had to lift it with my foot, or dab the brakes... Could it be that this sort of thing is happeneing to your car, only the other way around?

Also, is the rear axle tight on its mountings?