Sticking front brakes....

[Waylison]

This has got me puzzled....

Sometimes when I brake, the front brakes stick on, but a quick jab on the brake peddle frees them off instantly! A bit worrying for the car behind.

The calipers were supposed to have been rebuilt before I bought the car with new discs and pads.

I've pulled the pads out and can squeeze the pistons back easily, and they pump out again with peddle easily.

I've cleaned off the caliper faces in case the pads were sticking and put copper ease lube on rubbing edges of pads.

Still they sometimes stick.

It seems to happen when you only briefly use the brakes, if you use prolonged braking, ie, high speed to a round a bout, then all is fine.

I don't have a remote servo, the braking system is master cylinder direct to brakes.

Any advice please?

Wayne.

[David]

I've known this to happen with a remote servo - racking brains a bit - 'twas in a Scimitar about 20 years ago.

As I recall, it was the servo at fault - I think it was one of the non return valves sticking so that there was residual servo pressure even when the brake pedal had been released.


Presumably something similar would be possible on a close coupled setup.

David

[Greybags]

If the calliper pistons aren't sticking then it must be something acting as a valve preventing the fluid from returning.

Possible culprits... flexible hose intlernal colapse, master cylinder seal split/breaking up or foreign object in the fluid.

My feeling is that as it comes off if firm braking, then more return pressure from the disc/callipers, but light braking very little return pressure, so not enough to overcome the valve effect.

Is it affecting both front wheels, or just one?????

If only one wheel affected then more likely to be the flexible hose on that side, but if both wheels affected has to be something common to both circuits, so more likely the master cylinder.

Hope this helps...

Grahame

[Waylison]

Braking problem found!

I've just posted about taking car for pre Mot check (see other post).

While doing this I told Dave the mechanic about brakes and we spun wheels with front up in the air and applied peddle pressure, the wheel stopped spinning. He asked me to continue trying to turn the wheel while he released the peddle until he had completely come off the peddle, but I still had the pads gripping at the wheel, until he lifted the peddle up! It turns out that the return spring on the peddle becomes fully relaxed before it should. So that's the problem. So all I need do is reposition the spring and all should be fine.

Obvious when you think of it

Wayne.

[series4]

It would also pay to clean and lube the shaft from which the pedals pivot, and the clevis pin

Peter