I just uppgraded my brakes,rear disc conversion,and brembos up front,but i thought there was a leak of fluid somewhare,so took it back to the garage today.

Symptoms were very little braking power very spongy pedal,going almost to the floor,when pumped to stiffen up it could pushed to the floor with a kinda jerking motion.

The garage has called and said there is no leak!! and that it must be a master cylinder failure,but why would it sudenly fail??? the guy said he has seen it happen before when replacing brake parts the cylinder sudenly fails.

Has anyone else heard of this

Cheers Scotty

Check your brake fluid level if its below the low indication. If it is refill brake fluid. Did the make a vaporization to the brake system after the conversion?Try for a new vaporization. If the problem insists check again your brake fluid and if it is low indication take a look under the car for a leak.

whenever you do a brake conversion you never know if your master cylinder will be suitable. some brakes require more fluid to be pumped. the total fluid requirement of your braking system needs to be equal to or less than the amount of fluid your master cylinder pumps.

imagine your brake pedal moves 1/4 of its movement, that will equal a certain volume of brake fluid that is pumped from the master cylinder. bigger brakes almost always need more fluid, so effectively your master cylinder wont move the caliper pistons as far on the new brakes, that means braking effort is greatly reduced and your pedal can travel all the way before you even get good braking.

on brakes where the piston size increases the gap behind the piston is larger, so it needs more fluid to fill the gap and push the piston out. that will be the case on your brembos. you've also changed to discs on the rear, they need more fluid than the cylinders on the old drums did. add both these factors together and your master cylinder shouldnt be expected to pump enough fluid to satisfy all 4 brakes.

i've seen this happen before, the solution was to upgrade the master cylinder to a bigger one. since the HGT has rear discs i would suggest an HGT master cylinder is your best bet, or one from a marea with rear discs.

Yup we'd to upgrade the master cylinder when we vastly upgraded the brake setup on my friends sierra.

Thanks for the reply's guy's, it's sorted now,i personaly think they dident bleed the two bleed niples on the brembo,s properly, but he is still saying it was the cylinder.

I bought them from a guy that had them on his bravo with the rear disc conversion aswell,and they were fine on that with the standerd cylinder,so knew i dident need a bigger one,after he told me that i might add.


Cheers Scotty

do you find the pedal travels further than it did prior to the upgrade?
can you still lock up?
have you adjusted the brake bias valve to compensate for more effective rears?

its important that you maintain the correct brake balance and effort.

Hi Jug,the pedal travels about the same,if anything less,and i have been advised to avoide heavy brakeing and bed them in for a good couple hundred miles before giving them some jip, it was a garage that done the work,so i cant realy say if the brake bias valve was adjusted,i would like to think they did.

How/can i check this out,without asking him first??

Cheers Scotty

a brake testing machine (every MOT tester has one) will tell you if the balance is out of the permissable range. you should always do a test after a big job like this, better to identify a problem now rather than when you're doing 80mph into a tight bend.

jug said:

do you find the pedal travels further than it did prior to the upgrade?
can you still lock up?
have you adjusted the brake bias valve to compensate for more effective rears?

its important that you maintain the correct brake balance and effort.

Click to expand...

What adjustment? It's the same bias valve on pretty much all the Fiats of that era.. just uses the spring from the rear ARB to proportion the flow front/rear

the new rear brakes will be more effective, and so will the fronts, so you dont know what the relationship is between fluid pressure and brake effort at the front or rear. you need to make sure that brake effort is balanced between front and rear. on proportioning valves that are spring operated you can usually adjust the top bracket position. iirc my 1.8bravo didnt use a spring, it had a pressure valve that you could adjust, that is why i did not need to adjust it when i lowered the suspension. (if you have the spring type you must adjust it to prevent your brake bias shifting to the rear)

According to the EPER the 1.4 12v, 1.9 JTD 100 and 1.6 16v CF3 used a non-sprung bias valve.. all others used the sprung one..

i couldnt find the spring on my 1.8

jug said:

i couldnt find the spring on my 1.8

Click to expand...

perhaps it had sprung?

So does that mean it will be self adjusting??
Just out of intrest has anyone seen the rear calliper at the 10,oclock position on a bravo brava? like this
Cheers Scotty

Hellcat said:

perhaps it had sprung?

Click to expand...

ScottyJTD said:

So does that mean it will be self adjusting??

Click to expand...

yes it is self adjusting, when the rear has more weight the suspension drops, which opens the valve more allowing more pressure to act on the rear brakes, preventing a back end wobble under hard braking. lowered suspension means your back brakes are getting more pressure than they should.

ScottyJTD said:

Just out of intrest has anyone seen the rear calliper at the 10,oclock position on a bravo brava? like this
Cheers Scotty

Click to expand...

10o'clock on which side?

the rear caliper on an HGT should be behind the hub, so that would be 9o'clock on the driver's side and 3 o'clock on the pass side (on a RHD car).

for exmaple

The rear calipers and mounting brackets i have put on, are from a 2.0 Tipo ,and on the brava arm the caliper position is 10 o,clock on the driver side,and 2 o,clock on the passenger side .

Just wandering if anyone had seen or known this before?

Also am i write in thinking Fiat never done any model of the brava with rear discs ??

Cheers Scotty

the position of the caliper doesnt really matter, as long as it is securely attached and in line with the disc then its fine.

the brava never got rear discs because it didnt get the 20v engine.