Fiesta brakes - poor feel/effort

[kooder01]

My mini is a 92k sprite with the standard servo and compensator on the bulkhead, with a added adjustable one on the rear subframe to stop the rear from locking up under hard braking. The problem i have is i could probably stop quicker with my feet thro the floor!

I have bled the system completely, adjusted everything at the rear and im stilll gettting little effort. All the lines have been swapped for goodridge items.

Does anyone have any ideas??? please help!!

Gav

[Gr4H4m]

It could be loads of things... could do with more info. but you could check the following:

- Check the pads are the correct type. The XR2 pads look the same and fit, but they are slightly larger and catch on the carriers so you can't apply the brakes properly

- Are the callipers new? if not are they sticking (Pistons or sliders)

- Is your master cylinder working?

- Check for air in the sytem

- Are the rears adjusted up? this effects the ammount the pedal has to move massivly.

- If its a twin circuit system is that PWDA valve on the bulk head working? There is a shuttle inside which can change the front to rear pressure.

Thats all I can think of at the mo..

[kooder01]

Thanks for the reply! Ill got throught the points in the same order as you state them.

the pads are the correct type (ebc), however I do have some fast road pads on order to give a little more bite.

the calipers were refurbed before fitting them, plus i have recently had them in bits again to check for any problems when i could not get the effort.

the master cylinder is the only thing that i cannot say for certain if its working correctly, I split the cylinder from the servo when i was refurbing everything during the resto. when pumping the brakes with the engine off the pedal becomes rock hard (testing the servo operation) and everyhtihng else seems ok. I do have a spare setup that im am going to fit to see if thats the problem. Is there anything else i can check? Also I think i have the hoses plumbed correctly, does anyone know which way they are mean to go for certian? eg, which hose to which input on the bulkhead compensator (PWDA) and then from the compensator (PWDA) to which end of the car?

there is no air in the system, plus there is no tell tale spongy pedal

the rears are fine too, the first thing i checked.

how do you check if the PWDA valve is working correctly? I have never had a issue with these and thought they were pretty reliable.

the pedal feels fine when driving, but when you hit them hard it will not lock the fronts at all.

[Gr4H4m]

mm I'm not sure with the newer twin circuit systems but if its a yellow tag I did think that the unions were a different size so you cant get the pipes mixed up. If its a black tag I think they are the same size. I believe the black tag has the same size front to rear MC bore where the yellow is offset so there is more fluid being pushed to the front.

Have you tried standard pads? I don't run the fast road stuff they take too long to get up to temp, and until then do give you the feeling you wont stop... I use a good quality standard pad which even performed well at last years Miniworld action track day. You could try the swap.

On the PWDA Steve had some problems with his wifes car and had to change it, but I think it wouldn't let any fluid to the front. He might be able to advise better. I did do some reading on them and they can be a bit of a pig esp when power bleeding the shuttle can move about and stick. There not cheap to replace either..

Hopefully the guys with the newer cars can help with the twin circuit and PWDA stuff. It does sound like there isn't enough pressure going to the fronts.

[Steve]

1. Remove the filler cap from the master cylinder reservoir and top up the fluid level as required.
2. Attach one end of a bleed tube to the bleed valve at the left-hand front brake and immerse the free end in a small quantity of hydraulic fluid in glass jar.
3. Open the bleed,valve about three-quarters of a turn. Depress the brake pedal rapidly through its full travel and then allow it to return to the fully released position. Hydraulic fluid should have been pumped into the jar; if not, open the bleed valve further.
4. Continue depressing and releasing the pedal, pausing for a few seconds after each stroke, until the fluid coming from the bleed tube is completely free from air bubbles.
5. Finally, with the pedal held down to the floor, close the bleed valve. Take care not to over-tighten the valve; tighten it only sufficiently to seal. Remove the bleed tube and refit the dust cap on the bleed valve.
6. Bleed the right-hand front brake next in the same way, then the rear brakes, finishing at the rear brake nearest to the master cylinder

http://i7.photobucket.com/albums/y253/swdonnelly/bleedseq1.gif

7. Finally, top up the fluid reservoir and refit the filler cap, after checking that the vent hole in the cap is clear.
8. If even after bleeding, the brake pedal is still 'spongy' or goes right down to the floor, this indicates that air is still present in the system, and the bleeding operation should be repeated. If subsequent attempts at bleeding still fail to produce a satisfactory result, the system should be checked for leaks, as air is obviously being drawn into the system.

Dual Line Braking System

The dual line braking system may be split either diagonally or front to rear. However, in either case, the bleeding procedure is similar to that already described for the single line system, only the sequence of bleeding being different.
The bleeding sequences for the various dual line systems are shown in .
The pressure failure warning switch should be removed from the PDWA unit before commencing bleeding. When bleeding is completed it may be necessary to reset the PDWA as detailed under the appropriate heading previously.
On models which have a master cylinder with an inbuilt PDWA, if a new master cylinder has been fitted it may have a plastic spacer fitted between the pressure failure warning switch and the master cylinder body. The system should be bled with the spacer in position, then the spacer discarded.

http://i7.photobucket.com/albums/y253/swdonnelly/bleedseq.gif

Excessive brake pedal travel
1. Brakes need adjusting or replacement. 1. Adjust or renew brake shoes.
2. Air in system. 2. Bleed hydraulic system.
3. Leaking or contaminated fluid. 2. Bleed hydraulic system.
4. Faulty master cylinder. 4. Fit new master cylinder.

I would guess it is your master cylinder leaking fuild back into the cylinder. If all of the above are ok.

Servo (where fitted) late in operation
1. Blocked filter. 1. Clean or replace filter.
2. Bad vacuum sealing or restricted air inlet. 2.Tighten vacuum hose connections and check hoses.

Loss of servo action when braking heavily
1. Air leak in servo - vacuum low. 1. Either overhaul servo or replace.