The V8 Owners Forum -

Hi all, my car has a remote servo on a single line braking system, all callipers, wheel cylinders, master cylinder and servo are new.
When i press the brake pedal lightly, they stick on slightly (all 4 wheels) and eventually (3secs or so) come off again. Alternatively, when they are slightly stuck on I can release them by pressing hard on the brake pedal. Does anyone have any ideas about what is going on?
Thanks for any help.

Sounds like he might have forgotten to put a return spring on the pedal ?

Not that easy... unfortunately , return spring fitted and bringing pedal to stop. Also has clearance from push rod to master cylinder.

Have you used the car yet or is this just workshop tests? Maybe if they have a little bit or use they will loosen up a bit?

Hi
Do you have a residual pressure valve in line?
Do you have any really tight bends within your system and have you made the hard lines up yourself?
Also did you check that the pistons within the calipers are moving freely without the pads in place?
You can pop the pads out and put a thin block of wood between piston and disc and pump the pistons out and back several times to free everything up.
Sometimes the pistons will get a sort of rind between the seals and this takes a few in and outs to free up.
Hope this helps.
Cheers
Paul

Hi thanks Paul, no residual valve in line. I have made all brake lines myself, all flanges are good with no tight bends in system. all pistons are ok in callipers and rear wheel cylinders.

Hi Again
I'm assuming that the braking system is a matched unit from one supplier.
Have you checked that the pedal ratio is correct for the M/C you are using.
It may be possible that you have a dodgy seal on one of the cylinders that is allowing the fluid to back feed and causing this sticky problem.
Also how many outlets do you have on the cylinder from the servo?
Cheers
P

Hi, braking system is all willwood, ordered through rally design after speaking to Willwood about master cyl sizes ets.
Servo has single outlet.

Okay
All of that should be matched then.
The next thing is what pedal box are you using,willwood again?
If yes, is the box set correctly?
It must be something simple this problem.
P

It still has the original pedal box, which Willwood said had the correct ratio for their master cylinder, think it was 4:1 but cant be sure without checking. Am going to bypass the servo later and give it a go.

Okay
Let me know how you get on please.
Have a good friend who knows stuff and is an oracle on most things automotive and can give him a shout if we need too.
Cheers
P

I'd hazard a guess

The seal in the master cylinder is sticking in the "on" position
It can do this so long as there is not much pressure to push it back (Normally also have a spring also pusjing the seals back)

So stand on the pedal and the pressure is "big" so it will push the seal back - gentle and the seal will not move.

It could work itself loose

Or it could be an indication of seal failure - some seals do not like certain brake fluids - get the wrong 2 together and the seals will swell before collapsing

Could be worth a call to Wilwood to check if the fluid you used is compatable

Ian

Was the servo at fault, even though new! Ran a pipe to bypass the servo, bled brakes and took it on a run, no locking on and no more 'notchiness' (yes I know its not a real word) through brake pedal. Company replaced servo, fitted today and brakes now feel superb and pull up well Thanks for all your help guys.

Yahoo
RESULT
P