Brake Question

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domderbyshire

domderbyshire

Active Member
Posts
198
Location
Bracknell
Evening, All.

I recently had 4 new callipers, discs and pad sets fitted and the brake lines renewed. The garage obviously bled the system and I have allowed everything to bed in, covering a fair few miles. However, despite several bleeds since, I'm not completely convinced by the effectiveness of the system. When driving the brakes certainly stop me, but if I pump the pedal it firms up as expected, but when I keep pressure on the pedal the pedal then sinks away under my foot, before firming up again. If I pump the pedal before fully committing to braking, there is far less travel and the braking effect is very good. I would like to have this level of braking instantly.

Is my master cylinder tired? I've got no leaks anywhere and the whole system, with the exception of the servo and master cylinder, is new. The work was done by a highly respected garage, so no worries there.

Many thanks for your input.

All the best,

Dom
 
domderbyshire said:
Evening, All.

I recently had 4 new callipers, discs and pad sets fitted and the brake lines renewed. The garage obviously bled the system and I have allowed everything to bed in, covering a fair few miles. However, despite several bleeds since, I'm not completely convinced by the effectiveness of the system. When driving the brakes certainly stop me, but if I pump the pedal it firms up as expected, but when I keep pressure on the pedal the pedal then sinks away under my foot, before firming up again. If I pump the pedal before fully committing to braking, there is far less travel and the braking effect is very good. I would like to have this level of braking instantly.

Is my master cylinder tired? I've got no leaks anywhere and the whole system, with the exception of the servo and master cylinder, is new. The work was done by a highly respected garage, so no worries there.

Many thanks for your input.

All the best,

Dom
Click to expand...
if theres some free play in the pedal adjusting the servo push rod might help
 
domderbyshire said:
Ok. How do I do that, please?
Click to expand...
Have a look in there and you should see the rod with an adjusting and lock nut.
servo.jpg

It's tighter than a mouses ear to get a spanner in, so patience is needed.
 
Your pedal action sounds like the symptoms I had before rebuilding the Master cylinder. The genuine rebuild kit is cheap enough and it's a fairly easy job - just a bit fiddly.
 
Check the adjustment but I think zeaphod is on the right track,if pedal keeps going down and there is no external leak then fluid must be seeping past the master piston back to the res.
 
If you have rear drums, it's also worth checking for brake fluid under the rubber dust seals on the wheel cylinders. Even a small leak there - not enough to reduce braking power noticeably - can cause the pedal to drop a bit. The OP here has discs all round, so shouldn't be a problem.
 
Go back to the response from James, and adjust the rod before doing anything else, otherwise you will probably be chasing dead ends for ever!
 
domderbyshire said:
Ok. How do I do that, please?
Click to expand...
undo the 2 mc securing nuts ,pull mc away carefully,get someone to press brake pedal hold the rod with pliers so it doesnt pull out and screw adjuster anti clockwise a couple of turns, refit mc and try ,it may take several attempts to get right, if you adjust too far pedal will be hard and brakes will slowly apply themselves
 
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