75 not stopping

deano · June 29, 2009, 09:07:22 PM

hey guys,

after your thoughts on my brakes. basically the entire system has been rebuilt: calipers, master cyl, trw lucas pads, discs and braided lines front and rear. however the pedal is still going to the floor under heavy braking. the car suffers from horrific brake fade on track but the pedal is still going to the floor even when cold on the road. brakes have been bled and bled again with no real change and no air bubbles are coming out. i have also adjusted the rear pad clearances so that they are just grabbing. the pedal drops an inch before the brakes actually start to work and if i keep applying pressure, the pedal hits the floor and the rears lock. if i hit the pedal hard quickly, the fronts will lock. the pressure limiting valve next to the master has been removed because it was rusted.

where should i go from here? new master and p valve?

cheers

shane wescott · June 30, 2009, 12:15:04 AM

In a properly sealed hydraulic system you shouldnt be able to hit the floor. If you have bled the system then thee shouldnt be enough room for the pedal to compress all the way to the floor.

Are you sure you are not losing fluid at all. I would expect any leak in the system to lose fluid.

Not sure if an issue in the booster would cause this.

Sorry I cant help any more.

CAtch ya

Shane

Colin Byrne · June 30, 2009, 08:07:05 AM

Sounds like the seals in the MC have failed, in a duel circuit MC it's possible to have a failure between circuits so it will act as if there is a leak but no fluid will drop out of the system as the fluid can leak from one circuit to the other

flighty · June 30, 2009, 09:06:42 AM

Something like that happened to the Spider (we were having some fluid loss though, the fluid was getting burnt by the engine) - it was leaking through some failure in the Servo!

We changed that and the brakes were great. It took ages to work out, but you need to eliminate all the possibilities.

Go with the master cylinder first though!

meizhak · June 30, 2009, 10:48:45 AM

definately sounds like the master cylinder is bypassing internally

enzo1891 · June 30, 2009, 07:46:37 PM

check your brake booster, pump up the pedal about 3 to 4 time and see if the idle on the engine changes could be your are losing vacume pressure and hydrulic pressure.

deano · June 30, 2009, 08:30:22 PM

hey guys,

not solved yet. already tried pumping the pedal and didnt notice a change of idle. would the lack of the pressure limiting valve make a huge difference to the bias? it was ditched in an epic rush to get the car reged back in feb for winton. doesnt it determine front and rear bias? no fluid leaks under the car that i've noticed and reservoir stays full. holding out on a new master cyl until later in the week because of funds. dont want to hit the island (for the first time) this weekend without decent brakes...

enzo1891 · June 30, 2009, 10:30:46 PM

ok have you bleed the master cylinder on the benchfirst, and also you do know that the rear calipers have bleed nipples per caliper you should start on the right hand rear caliper, then to the left hand side also another thing i sould ask is when you say you have adjusted the calipers for the rear you have done both the inner pads and outer pad adjustment.

Paul Gulliver · July 05, 2009, 09:44:30 PM

Deano,

You might of had trouble getting the 75 to stop last week, but the other pedal (the loud pedal) was certainly working at Philip Island on Saturday. I think you said it was your first AROCA sprint, second of any kind of sprint and first time at the Island.

A 2 min 9 sec and first in class on a damp track was an outstanding result. Your offs looks exciting to.

Keep up the great work.

Cheers

Gully

Sheldon McIntosh · July 05, 2009, 11:01:14 PM

http://www.natsoft.com.au/results/

deano · July 06, 2009, 01:43:19 AM

hey guys,

had a ball at the island. a mad track thats for sure!

cheers paul, cant believe the time. its the car not the driver thats for sure, hence the offs and sideways action! chucked two yoky 0032 on the rears for the last few runs after a screw found its way into one of my road rears and the difference/confidence they gave me were amazing!

mick, i reckon you're right. sorta feels as though fluid is leaking from the system when i push hard on the pedal slowly when stationary. new master for sure. thought we fixed it on friday night cause pedal travel was much better after adding an extra seal to the master. its all back again. had to exit the track a few laps early on the last run cause my brakes decided they had enough into honda. drove home with almost no brakes. nice video on youtube btw. wish i had time to mount a camera. instead i spent friday night lying in brake fluid in the garage trying to get a clutch...

is it possible to fit a master off another bigger heavier car as long as it has the same bolt pattern? any ideas on after market bias valves/bars?

deano · August 05, 2009, 12:31:03 PM

hey guys,

decided to man up this week and fix my brakes. picked up a new bendix master and willwood biasing valve. going to chuck them in on friday so hopefully it will bring an end to my rear wheel lock up and firewall hitting pedal.

going to set about making a small cage for my camera so hopefully i'll have some video on monday fingers crossed

deano · August 13, 2009, 10:44:23 PM

even a new master and bias valve didnt help. at winton on the weekend i spent most of my time with my middle pedal on the floor and visited the dirt a few times as a result.

to recap:

new bendix master, willwood biasing valve, reconditioned calipers, braided lines, new trw lucas pads, new rear discs, fronts a year or so old, no leaks, no change to idle speed when pedal is depressed, rear calipers adjusted properly and i cant count the hours spent bleeding it all.

the only thing i did notice is my handbrake is really far up and is fairly hard to adjust due to the worn cable and it only just works on the highest notch. i'm lost on what to do next. due to a lack of money i'm thinking about attempting to build my own pedal box over the next few months for it either that or i'll save up and get one made cause my fabrication skills arnt the best. what are they worth?. if i move up to volvo 4 pots, i'll have to go back to my 16 inch road tyres cause my 14 inch r specs wont fit over them. and then to do that i'll have to put some suspension on it to stop tyres rubbing on the top of the guards.

how hard can it be to make an alfa stop??? whats next?

either way i'm going to chuck the car in the shed till PI in dec so i have the chance to save up for another road car.

cheers