brake problem

[SPS]

Denny:
GP is correct about the master cylinder size being important. We usually use the Chrysler style master cylinder available from Wilwood for these systems. Also, Wilwood also has an in-house manufactured master made for manual disc/cisc systems that is very good but more expensive.
The geometry issues brought up are also correct.
Finally, either vacuum or low pressure bleeding the system will save a lot of aggrivation. You didn't mention, but location of the master cylinder (firewall or floor mounted) will make bleeding more or less difficult.
Barring that, you could just have a defective master cylinder.
FJ

[ron mattson]

i had a very similar problem on my friends firebird with the same brake setup as you have and it was a defective master cyl it seemed to be getting air bound on the return pedal travel. you could actually hear hissing coming from the master..new master solved all the trouble ..

[Jim Blankenship]

the push rod isn't hitting till 3" from floor ?
should hit with just 1/2 " down any closer it won't let mc piston to fully return

also take the prop valve out till you have brakes blead.
i put one on johns car when went aftermarket 4 wheel disk had LOTS of prob's, it in box in trailer now
car stops good no wheel lock up
it had a soft pedel with the prop valve on it
hope this helps
jim

[gmonde]

sounds like a master cylinder problem,try this ,plug all four lines at the calipers(you can do this with plugs for #4 line ,this dead heads the master,(i asume that you have braided lines)if the master is bad you wont be able to get a pedal no matter how much you bleed at the lines,if the pedal is hard,hook up one line at a time to the calipers could be a caliper piston lip seal not holding the piston out to the pad

gmonde

[Mike Hedger]

First off the corvette master cyl. was designed for a car with 4 piston 4 wheel disk brakes so it moves enough fluid for the willwood callipers but it is not a quick take up like the Chrysler unit so it needs all of its stroke to move the amount of fluid you will need to stop the car. Second you said the pushrod is not hitting the MC piston untill it is about 3" from the floor? If this correct that is your problem, make or buy a longer pushrod. I like to give the MC about 1/4" of freeplay so you don't cover up the compensating or return ports otherwise you will have pressure on the system at all times. Hope this helps and have a merry Christmas, Mike

[Dave Goob Cook]

Gotta have full stroke.
Full bottom and full return first and foremost, with positive retention of the pushrod in the M/C please!!!!!

No need for the valving, but it won't kill ya either.....

Any factory valves have been removed, correct?

M/C is higher than the calipers?
Lines need to not run "up" at any point out of the M/C. (Line-Lock or pressure gauge plumbing?)

Bench bleed, install M/C keeping the outlets turned "up" as much as possible, while you finger in the lines, mount it, leave the lines cracked just a touch while an assistant strokes the pedal all the way down and holds it, while you snug the lines. Then gravity bleed it at all 4, shut off as fluid flows to each one, then start a "normal" bleed process.

Sometimes if the lines have been flushed or dry, you should open all bleeders, stroke the pedal full down and hold, close bleeders, let pedal up, repeat as needed, to get as much air out initially as possible.

I've had to do brakes alone for years, found some tricks. I've replaced many M/C's without the need for any bleeding, only flushing out of the old fluid....
Speaking of that, the lines were clear and dry, no kinks or dents, no excess moisture around when the system was open?
Any possibility of fluid contamination?

Remember that some braided steel lines (non hard Teflon liner) will give you a spongy pedal, and the brake pedal never feels "hard" enough until the new pads/shoes are bedded in properly.

IF you are using a Silicone fluid, there are more details to follow.
Been there, done that, nothing wrong with it at all, you just have to treat it differently.

I like Valvoline Synpower brake fluid.

[denny harvey]

OK,the MC looks like its getting full travel at the push rod,i checked the depth on the bench and in the car.the pedal at rest is 41/2 to 5 inches off the floor.so now i will plug up MC and see if it holds..i hope its a bad MC..any of you camaro guys had to change the push rod when switching to disc ???

[Joe Martens]

Denny, I replaced the stock master cylinder with a Strange master cylinder and I have 4 wheel disc brakes. It has the 1.125 bore, part # is B3359BK, which comes with adapter fittings and a pushrod with a rubber sleeve at the tip so it keeps it inside of the piston. I do not run a proportioning valve. I have not had any problems.

[denny harvey]

OK,the MC holds a strong pedal when i dead headed it ,i called wilwood about the pushrod and they told me how to measure it ,it also is ok.?? so i guess the system is full of air..now to get it out.thanks for the help guys...and i thought my soft-loc clutch set-up was tough........

[Kevin Lang]

Denny, check the adustable prop valve to make sure it is not closed up, by turning the knob somewhere close to center on the adjustment. Otherwise you will have less pressure and slow bleeding at rear brakes thus taking forever to get the air out. good luck!!!