brake problem

[denny harvey]

I put wilwood 4-wheel disc brakes,a new corvette master cyl [ non power ]and wilwood prop valve to the back brakes..all new stuff...there seems to very little line pressure when bleeding brakes..i have no pedal. do i need a different push rod,the stock drum brake rod is the one on the car..seems like a bad master cyl but it is new..any thoughts,,thanks

[Joe Martens]

Did the brakes bleed o.k? Sometimes gravity bleeding the brakes works real well. Also, make sure the pushrod is far enough into the master cylinder. Hope this helps. Good luck and Merry Christmas.

[Bill Grubbs]

Did you Bench bleed the master cylinder? If not it will be nearly impossible to get full pedal pressure.

[denny harvey]

i did bench bleed the MC,when bleeding the brakes,the fluid does not seem to come out in a fast stream..i will try to gravity bleed them today..the push rod hits the MC with the pedal about 3 inchs from the floor.car has all new brakes,lines.line-lock ,prop valve and MC,so i must not be getting all the air out or MC needs ck...also there are no leeks that i can find..thanks for input guys..back to the pole barn..man ohio is cold and windy..lol..

[Tailchaser]

Make sure the linkage allows the piston in the M/C full return. The geometry on the end of the pushrod may not properly fit the cavity in the rear of the piston?.thus not allowing the piston to fully return. It also may be too long, creating the same problem. If all of this is OK, then start over with "bench" bleading the M/C and follow on with the balance of the system.

All of the caliper bleeders are at the highest point correct??..higher than the lines entering the caliper?

[Greg Hill]

Make sure the bore diameter of the master cylinder is the right size or you won't have much of a pedal. I would call Wilwood to find out for sure but I think it needs to be around 1&1/8.

Greg

[denny harvey]

thanks again for your input guys,the master cyl is a manual 67-74 vette with a 1 inch bore,wilwood said this would work..when i start bleeding the brakes, i bleed the pass side rear first.i get a little pedal,but by the time i get to the other side its gone,its like starting over at each wheel???? when we pump up the brakes and open the bleeder ,the fluid has little pressure behind it.....bleeders are higher then the lines..have a good holiday guys,im done working on the car till after x-mas,maybe santa can help...denny

[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