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        General >> Problems >> brake problem 
        
(Message started by: cuzza on Jan 18^th, 2008, 7:21pm)

Title: brake problem
Post by cuzza on Jan 18^th, 2008, 7:21pm

hello everyone ....i have a brake proplem on 24v i am restoring i have put on new disks and pads all round changed brake pipes on back and also front drivers side and new flexipipes ...brakes have been bled as per recommended ....however brake pedal is soft for first half of travel when engine running ....without engine running brake pedal is solid with minimal travel as you would expect on a auto ...i have tested servo and no proplems there (pedal comes straight up when you stop engine) there are no leaks anywhere and i am suspecting master cylinder as i changed the fluid in the system and master cylinders are fickle at the best of times .
can anybody offer advice before i change M/C :)
ps happy new year to all

Title: Re: brake problem
Post by scorpio_man on Jan 18^th, 2008, 7:35pm

hi there

to me, it sounds like air is still in the system. i'd have another go at bleeding them again. :-/

hth

Title: Re: brake problem
Post by cuzza on Jan 18^th, 2008, 8:05pm

i have bled brakes 4 times ....same result each time ???

Title: Re: brake problem
Post by TiberiuS on Jan 18^th, 2008, 8:25pm

Long shot but a possibility that there's some air trapped in the ABS pump if you had the system drained? :-/

I know it can happen and there's a way to purge the pump via software but it's normally when the pump has been stored and drained.

Title: Re: brake problem
Post by scorpio_man on Jan 18^th, 2008, 8:29pm

hi there

how have you bleed them? there's two ways. see http://www.fordscorpio.co.uk/brakesmanual.htm

hth

Title: Re: brake problem
Post by harry.m1byt on Jan 18^th, 2008, 8:39pm

A few suggestions...

1. The pedal will feel quite soft when the servo is working, compared to no servo action.

2. New pads and disks will give this feel, until they settle in anyway and properly conform to the disk.

3. Are you sure you don't have a pad misaligned, or a backing strip to the pad (what's the correct name for these?) - I'm thinking along the lines of perhaps a pad not being square to the disk, being pushed against the disk and springing back again when you take your foot off the brake. That would cause extra pedal travel.

4. I think I read something on this site about the braking system (ABS unit ?) being quite difficult to bleed fully.

Title: Re: brake problem
Post by cuzza on Jan 19^th, 2008, 3:47pm

thanks all ;D i have car upon 4 stands for easy access and have had everything in and out several times system was never drained of fluid, but all fluid has been changed by purging ... i now wot your saying about disks and pads and brakes work well but going for MOT soon and i just know it will fail on excess travel .....i am unsure about the two ways to bleed brakes ....would bleeding brakes with car running make any difference ?
think i will replace master cylinder and see wot happens cannot over do it when it comes to brake 8)

Title: Re: brake problem
Post by TiberiuS on Jan 19^th, 2008, 4:39pm

That's how I do mine, purge the fluid from furthest to nearest wheel with an Ezibleed working from the spare tyre. My ABS pump was wrapped in a plastic bag and left in the boot for over a week so lost quite a bit of fluid and I didn't have any trouble with air in it afterwards...I just heard that it is possible for the air to get caught in there :-/

Good luck, hope you get it sorted :)

Title: Re: brake problem
Post by harry.m1byt on Jan 19^th, 2008, 6:23pm

Cuzza....

You mentioned its an auto - the fact that it is an auto makes absolutely no difference to the feel of the brakes.

You say that you have it up on axle stands - could you perhaps get someone to watch i turn, each of the four sets of pads for movement as you press the brake with the engine running? That is just to confirm that nothing is moving/ bending/twisting as you apply the pressure.

Regarding the extra travel when the engines runs versus minimal travel when its not...

In my younger days I too was fooled by thinking that the soft pedal might mean air in the system - when I first came across servo systems. If I'm in any doubt now, I test it without the engine running. If there really is air in the system it will certainly show up without the servo in action. If the pedal is solid, doesn't pump up nor gradually go down under sustained pressure - then it is as it should be.

Remember once it is actually on the road, it will feel completely different - in that you will be barely touching the brake pedal to stop the car.

In other words I'm fairly confident the sponginess you are describing, is simply you comparing the servo action versus the no servo action - the actual sponginess is simply the flexible pipes swelling and calipers bending slightly due to the extreme pressure you are applying via the servo.

If it feels solid then, I accept it as being OK. Take for a bit of a run, bed the brakes in and then reassess the spongy feeling.

On the subject of brakes, it is a good test of the system to apply extreme p3
ressure on the pedal occaisionally with engine running and car stood - as a pressure test of the system. Better to provoke a pipe or hose to burst when you are stood, than on the road.

Title: Re: brake problem
Post by mr._floppy on Jan 20^th, 2008, 5:48pm

I would give the new pads a few dozen miles to bed-in then deal with the spongy pedal later.

What bleed system are you using ? those one-man kits are quite good.

Remember them pesky pimples on the rear pads, makes sure they are aligned
with the cut-outs in the pistons . ::)

Title: Re: brake problem
Post by TTPmaverick on Jan 20^th, 2008, 9:23pm

a quick tip if you clip of your flexy hose's 1 at a time and push your brake pedal if you get a good pedal on 1 but not the other 3 the problem will be with that brake

Title: Re: brake problem
Post by harry.m1byt on Jan 20^th, 2008, 9:32pm

on 01/20/08 at 21:23:56, TTPmaverick wrote:

a quick tip if you clip of your flexy hose's 1 at a time and push your brake pedal if you get a good pedal on 1 but not the other 3 the problem will be with that brake

Good point!

You can either get a special hose clamping tool, or (carefully) use a self grip wrench by covering the jaws with something soft so it doesn't damage the hose.

Title: Re: brake problem
Post by cuzza on Jan 27^th, 2008, 6:39pm

:)thanks every one will let you know what happens after checks ....... 8)