[rew]

Car's brakes have been very effective but pad and disc wear was excessive so I have replaced all round and the car has now passed its first MOT - good! Having changed brake parts I have been using them gently and occasionally more than that to bed them in and have noticed things I wasn't previously aware of:

Brake pedal sinking with engine running, at the traffic lights for example. Sink is slight and seems to be a feature of many auto TD's of many makes. Saab issued a bulletin about this (522-2732) discussed on this forum - http://www.saabscene.com/forum/archive/index.php/t-144070.html?

More interesting perhaps is that if I brake gently nearly to a stop and then rapidly pump the brakes to come to a halt, brake pedal becomes hard as if I have beaten the servo and vacuum pump's ability to support the brakes! Any normal braking is fine, ABS works and I can stop very rapidly.

Can any one else repeat this characteristic? Is it normal to be able to "beat" the car's ability to create vacuum? I would be interested to hear if this is within the normal scope of the braking system.

 

[the zohan]

big heavy autos eat braker disks and pads due to little or no engine breaking effect. most cars i have driven have had the brake pedal 'sink' a tiny bit when you rest your foot on it, as long as it 'pumps up' when you press it a few rtimes all is well.

sometimes when braking down from reasonably high speeds the pedal gets a little wooden, i will upgrade the pads when they wear out.

 

[rew]

That sounds similar zohan, thanks. It is reassuring if others observe or experience the same thing!

Any one else try this or have a view?

 

[jezz1]

All diesels suffer from soft pedals if you press hard while stationary - it's called "diesel creep":

http://www.brakesint.co.uk/technical.html#techNote202