Please help before I kill myself.

[LowBuckX]

I converted to rear disks and now have to pump up the pedal everytime I let off. Hear is what Im running.
68 Vette disc/disc master
front from master to a "T" out to the calipers.
Rear from master into a wilwood adj prop to 85 camaro front calipers mounted on steeltech brackets.
It acts like the new master isnt holding any residual pressure?
What do you think?

Conversion is modeled after this http://www.chevelles.com/forums/showthread.php?t=115940

[LowBuckX]

.

[andrewb70]

First thing to do is make sure that the system is bled and ther eis no air. The second thing to consider is that your rear caliper piston area might be a bit on the large side. So the MC is not sending enough volume of fluid for proper caliper function. Just some thoughts.

Andrew

[LowBuckX]

I think now I had an air bubble and maybe stiol do. I Vaccume bled them power bled them and nothing worked. I put a set of Russell Speed bleeders and now I have some pedal. I will need to run some more fluid through this weekend. Im content now that it is coming back.

[6'9"Witha69]

Did you bench bleed the Master? It can cause some really painfull bleeding times if you didn't.

[LowBuckX]

Yes I did but Im not sure it bled well enough Ive built a vaccume bleeder that works a bit differant Im going to try this tonite

[quadfather]

here's somthing to check . does it happen if you just let the car sit for a minute ? . or only when you drive it? the reason i ask is when you run a c-clip style axle. the axle move's in and out a little bit . and if your calipers don't float freely enough , they will collapse the piston just a little each time the axle moves. i have even seen bent axle flanges do the same thing when the rotors wobble. if it happens without driving the car then the problem is most likely an air or volume issue . hope this helps.

[paul67]

it could be the masters worn , had this once hit the brake car stops take foot off ever so little the pressure goes and pedal goes down a bit till the car stops did this till you had no peddle and had to pump the brakes .

[LowBuckX]

The Master is a Napa remaned 68 vette disc/disc master with a 1.020 bore. I beleive the 68 vette have 4 piston calipers on all 4s like the jl8 Camaros so volume shouldnt be and issue.
Ive ran about 1.5 of the 1qt bottles through so far with a small amount of gain. Im going to try and built a pressure bleeder that constantly supplies more fliud as it pushes so I can do alot at once instead of a few ounces at a time.

I did a seach on a few sites and this seams very common to have to pump large amounts of fluid through the rears to get a good pedal.

[LowBuckX]

here's somthing to check . does it happen if you just let the car sit for a minute ? . or only when you drive it? the reason i ask is when you run a c-clip style axle. the axle move's in and out a little bit . and if your calipers don't float freely enough , they will collapse the piston just a little each time the axle moves. i have even seen bent axle flanges do the same thing when the rotors wobble. if it happens without driving the car then the problem is most likely an air or volume issue . hope this helps.

This is all static. Axles have very little runout. I tested with a magnet base and dial indicator.I did try and run it down my street today. (No traffic) I had enough to stop and could panic stop if needed but no real pedal.

[curt70]

what is very little runout? a carpender may think 1/32 " is small , very little to a machinest is .0005"
factory spec for four piston chevys is .001 flatness and .0005 parallelism and lateral runout is .004

Curt

[LowBuckX]

Being a Fabricator/machinist I know what you mean. Im fine on that.