Technical Variable brake pedal travel

[neilmeansneil]

When I start a journey i have a soft brake pedal, the brakes work okay and they don't bind. On most journeys after 10/20 miles the brake pedal firms up and the brakes start to bind a little. It doesn't happen every journey and seems worse after stop start journeys. It has new discs and calipers on the front a few months ago when it was MOT'd and an occassional sticking handbrake. Where do I start to look for a fix. Thanks Neil

 

[portland_bill]

Quite possible that you have a brake hose that is breaking up inside. The inner lining separates and works like the valves in our arteries, allowing fluid to pass one way only. This holds the brake on. After a longer stop, the fluid pressure has released as fluid gently leaks back.

Drive it until it starts binding.
Now raise one wheel and try to rotate it. If time before it cools or releases, try the other side. Start with the front wheels, check the rears if the fronts appear ok.

 

[GPz750]

Google how the servo works

 

[portland_bill]

Google how the servo works

One way to test the servo would be to temporarily disable it. BUT! This needs care, as braking effort will be considerable, so not near any steep downhill areas.

Disconnect the servo vacuum pipe so that the servo is not operational. Drive gently, applying the brakes frequently, to see if the fault is now not there. Keep speed low, and in an area with light traffic and plenty of space to park. Pedal effort will be high.

Make sure you plug or otherwise seal the vacuum pipe, or it will suck enthusiastically. If a petrol engine, it will seriously weaken the mixture and confuse the ECU, on a diesel it will allow the vac pump to overwork, potentially causing damage or excess wear.

DO NOT attempt this if at all unsure.

 

[varesecrazy]

When I start a journey i have a soft brake pedal, the brakes work okay and they don't bind. On most journeys after 10/20 miles the brake pedal firms up and the brakes start to bind a little. It doesn't happen every journey and seems worse after stop start journeys. It has new discs and calipers on the front a few months ago when it was MOT'd and an occassional sticking handbrake. Where do I start to look for a fix. Thanks Neil

which brakes are binding..? - just the fronts..??

 

[Zog]

Should be easy to find out which brakes are binding - the hub/wheel will get "warm".

 

[Thefox]

Make sure the cross shaft on the bulkhead behind the engine that joins the pedal box to the servo isn't sticking. Common fault. Access isn't easy and finding a capable garage is probably even more difficult.