strange problem

[car.crash]

not sure what to title this as due to the problem.
my brakes feel pretty rubbish and no feel to them, i have changed the pads, discs, all 4 calipers for good working ones off my old car, brand new master cylinder aswell and pressure bled countless times also i have fitted a rear bias valve off my old car. i also noticed that when i press the brake pedal when the revs are at lets say 3k i hear a noise coming from the rear of the car, either the fuel pump or the bias valve, it sounds like air escaping :confused:. when the car is at idle the noise goes when the pedal is pressed. any ideas on what might be going on?

[J$£5GTT]

didnt Oli have the same problem?,turned out to be the servo i think...?

:)

[car.crash]

thanks J. i was thinking my servo may be shot due to it being the only thing left and the bad feel on the pedal, but cant work out why im hearing noises to the rear of the car?
also if i hold the revs at 3k then push brake with my left foot the pedal feels normal with nice assistance but rev a little higher and the pedal goes rock hard.

[Mart]

If you pump the pedal whilst the engine is idling & the idle drops off/heavily fluctuates, or engine stalls altogether, it'll be the servo.

[car.crash]

i shall check that. thanks mart.
whilst were on the subject. how do i change the servo? will i have to remove all the brake lines from the master cylinder or can i slide the cylinder off the servo with lines attatched?

[Tony Walker]

If your accelerating then the engine isnt going to be producing much of a vacuum. What vacuum do you get at idle?(if you have a boost/vac gauge plummed in) i think at idle it should be about 20hg if you press the peddle a few times it should firm up as you press it and deplete the vacuum stored in the brake servo. The rear bias valve is usually the cause of a crappy pedal feel. if you try moving it make sure its not seized, setting it up is difficult unless you know the correct procedure, but if you put it all the way forward then try it all the way back and see how the brakes feel. bearing in mind that your changing the balance front to rear and could possibly lock up the rears or front brakes much easier. (make sure its a straight road with no-one else aroun ;)) If your cars been lowered then u may have to extend the rod for the bias valve.

[car.crash]

vacum is around -20 maybe more, i will have to report back on that.
the rear bias valve was broken so i took the one off my old car which i beleived to be good but not definalty. i have adjusted the rod to what i felt was about right. when the cars on the floor the valve has some travel before its fully open but its just a guestimate. i have checked the brake fluid levels and they have not dropped so the noise from the rear is not fluid leaking. to me it sounds like the fuel pump is working harder when the pedal is pressed down when at higher revs.

[car.crash]

im still having issues with this noise problem. its a very loud hiss when i press the pedal but only when moving. i have slackend off the bias valve and the noise stays the same and both left wheels lock up but the rights wont and the car weaves badly when hard braking at speeds.

[HULK]

Marc def sounds like the servo is shot. It's not a very hard job. You must remove the inlet manifold to get at it though

[Tony Walker]

sometimes the seal on the pedal can leak. never had to look at a 5's to be honest, but principle is still the same, the rod connecting to the servo should have a seal around it, ive known these to leak before, more so on scenics, but it doesnt usually have much effect on braking performance. Unless its leaking massively and your loosing all your vacuum assistance.

[Os8472]

Marc def sounds like the servo is shot. It's not a very hard job. You must remove the inlet manifold to get at it though

Piece of cake job to do, you will loose quite abit of blood though lol

[Os8472]

This is what mine was doing

http://www.youtube.com/watch?v=rdu5G7Z8M0Y

[car.crash]

Thanks guys. Ollie that noise is similar to what mine is doing but mine is definatly coming from the rear of the car.

[Os8472]

Thanks guys. Ollie that noise is similar to what mine is doing but mine is definatly coming from the rear of the car.


Get someone listern out while you press the brake, they might be able to narrow it down abit.

Mine was a knackered servo, the rod that pushes into the master cyclinder had broken off so the brakes only worked due to vacuum pressure so if I ever stalled it while driving I'd have had no brakes at all:eek:

[Alastair]

Marc def sounds like the servo is shot. It's not a very hard job. You must remove the inlet manifold to get at it though

No need to remove the manifolds to change the servo. It is only held on with 4 13mm nuts inside the drivers footwell. Remove the M/C and brake lines, undo the 4 nuts and brake pedal to servo rod pin.

The hardest part i find is getting the servo out of the engine bay, and the new one in. I found whipping off the drive shaft (dont forget the roll pin ;)) and dropping it out the bottom fairly easy. Another tip - before bolting the M/C back to the servo put a turn on each of the brake line unions while you can jiggle the M/C, saves a lot of time if your brake pipes are stiff/short :agree:

[jesus in the seat of a 5]

No need to remove the manifolds to change the servo. It is only held on with 4 13mm nuts inside the drivers footwell. Remove the M/C and brake lines, undo the 4 nuts and brake pedal to servo rod pin.

The hardest part i find is getting the servo out of the engine bay, and the new one in. I found whipping off the drive shaft (dont forget the roll pin ;)) and dropping it out the bottom fairly easy. Another tip - before bolting the M/C back to the servo put a turn on each of the brake line unions while you can jiggle the M/C, saves a lot of time if your brake pipes are stiff/short :agree:

:agree:, thts the way i did mine...:), forget the manifold buddy, this is much easier..:agree:

[car.crash]

thanks alistair. i think i may have found the issue but if it does not work this will be the next part to be changed.

[LYNCHSTAR]

thanks alistair. i think i may have found the issue but if it does not work this will be the next part to be changed.

i had the same problem before i changed my brake lines for an MOT the car was fine until i changed my calipers and brake lines did everything right tried a good servo even a new master cylinder. the car had realy crappy brakes when peddel was pressed. when you bleed the car make sure the brake bias lever is pushed right back with a zip tie i had so much air in mine it did my head in.

[car.crash]

im pretty sure its not air. when i checked the bias valve it was wound pretty tight. i have slackend it off to about half way as thats all thats left on my adjuster rod. i will drive it again and see if i have better brakes and try to find why i get a majour hiss from the rear of the car when the pedal is pressed.

[car.crash]

problem solved. the bias valve was wound up to much. took the car for a drive after i made it more slack and the noise from the rear slowly died down and seems to have vanished and i have proper brakes again. thanks for all the advise :)