Evening chaps, wonder if anyone can shed some light on a brake problem I've got.
When the cars not running the pedal is fine, then as soon as I start the car I can push it right to the floor!
Thinking it must be a leak of some sort but haven't got a clue really. Any help appreciated.


Matt

 

Brake fluid leak maybe?

What car you got

i guessing from your name a fiesta? Wa mk lol

 

theres a small chance it could be the master cylinder leaking,or a servo problem possibly.but im no mechanic.

 

It is a mk3 fiesta with cossie brakes front and back, braided hoses, and a mk5 escort servo conversion. It used to do this before I changed the servo and put the rear brakes on but it has just got worse. I cannot see any fluid leaking anywhere, but I'll have another good scout around.

Also if I pump the pedal while the car is running the revs go up but the pedal doesn't really get hard!?!

Thanks

 

The rear disc conversion will make the pedal feel a lot worse because of the extra surface area the pistons occupy. Plus the fact fiesta master cylinders are very small.

Also, are you sure the system is fully bled, its very common on escorts with disc conversions on the rear to get air trapped in the system even though they appear to bled fully.

 

is the master cylinder even big enough to displace the amount of fluid needed now for discs all round...?

 

Have you seen a fiesta MS? They're pea shooters

 

It has the master cylinder from the mk5 escort van that was with the servo, which is a lot more meaty than the fiesta one. I'll try giving them another bleed tomorrow.

The strange thing is that the pedal is rock hard with the engine off, then go's straight to the floor when I crank it up?

 

What brakes are you running then?

Rear disc conversion?

The pedal will be hard with the engine off, becuase there is no servo assistance, as soon as you fire up the servo is using the engines vacuum pressure to reduce the effort needed on the brake pedal

Also if the pedal goes hard as soon as you switch off your brake servo is on its way out, it should take a few presses to go hard if its ok.

 

I've got 4x4 cossie front brakes and xr4x4 rears with the fiesta centre conversion kit.

Like I say I'll have another go at it tomorrow and see how we get on.

Cheers Mate

 

Can you get a picture of the rear calipers, and indicate where the bleed nipple is?

 

take both the calipers off the back and wind both pistons fully home .
then put a g clamp on the piston or even get a m8 to hold the piston closed with a pair of grips. hold the caliper so the nipple is at the highest point and bleed the brake, this will ensure there is no air trapped in the system.

 

I'll give that a try, didn't do anymore at the weekend, also having trouble with my digicam so no pics