Help too much travel in brake pedal!!

[Just wheels]

Have '66 Coronet.
Had manual drums
Converted to power and front discs
All new parts from Pirate jack including proper master cylinder, proportioning valve/metering valve. booster.
Checked plumbing, all plumbed correctly.
Brakes have been fully bled (multiple times, now at brake shop and he bled again)
Car stop perfectly

But pedal goes almost to floor before engaging brakes. Car stops when pedal is about 1/2 and inch off the floor. There seems to be no brake engagement for the first 2-3 inches of brake pedal travel

UGH!

Anyone know the fix?

 

[440+6]

Did you adjust the rod from the booster to the master cylinder?

 

[Just wheels]

I did not, but the shop it is at now tried it, just a little and the back brakes locked up

 

[black64]

I believe the pedal ratio is different from manual to power brakes this could be a reason. Also if the bleeders on the calipers are at the bottom instead of the top there could be air trapped.

 

[Just wheels]

I believe the pedal ratio is different from manual to power brakes this could be a reason. Also if the bleeders on the calipers are at the bottom instead of the top there could be air trapped.

Put the power brake linkage at pedal as well, that's required, is that the ratio you are referring to? I'll check bleeders.

 

[Just wheels]

Bleeders at top. Frustrated.

 

[RT K_line]

How does the parking brake engage. I usually push the pedal down 3 clicks then adjust the rear shoes untile there is some drag when spinning the tire, other than that, the master may not displace enough fluid. I have read some threads that said there are different size pistons in the master.

 

[440+6]

Make sure your rear brakes are adjusted properly, too much play can cause allot of pedal travel

 

[dvw]

Vice grip all 3 rubber flex lines. Is the pedal good? If so you have to much pad travel,shoe travel, or air in the system at the wheel. Take one vice grip off at a time to find the culprit. If the pedal is still low with the vice grips you either have the wrong pedal ratio or too small a master cylinder bore.
Doug

 

[Just wheels]

All good ideas, thanks dvw, 440+6 RTK and others. Will try these. MBM/Pirate Jack site also recommends bleeding the calipers off the mount, tilting the bleeder to top to make sure no air gets trapped.

 

[bc3j]

Just a thought, was the master cylinder bench bled?

 

[black64]

Bleeders at top. Frustrated.

If bleeders are at the top and pedal ratio is correct next thing is does your master cyclinder have residual valves for the rear brakes usually 10 psi for drums and 2 psi for disk? Most have residual valves in them but might want to make sure on the master part number you have.

 

[MoparMikey]

The master supplied has too small of a bore. Increasing bore size decreases pressure/increase fluid moved and the pedal travels less distance to do the same amount of work. As an example, on Chevys with large front calipers (2 15/16" pistons) going from a 1" bore master to 1 1/8" bore master will raise the pedal about an inch and a half when engaged.

 

[Kern Dog]

You can buy pipe plugs to block off the brake lines at the master cylinder. This keeps all fluid and pressure in the master cylinder itself. Firm pedal? The problem lies downstream either with the lines, the calipers or the rear brakes.
Oh, are the wheel bearings properly adjusted? Loose bearings allow more movement of the calipers.

 

[Just wheels]

Pirate Jack sent new Master Cylinder and Proportioning valve/metering valve. Going to try the new master cylinder first, then work my way through the suggestions. Thanks for all you help!

 

[rrTor-Red]

Just a thought, was the master cylinder bench bled?

I was just going to ask that question myself. That would be the starting point. Air can be still trapped in the M/C where as the pedal travel can't expel all of the air. That's why they say to bench bleed them FIRST and push piston all the way in.

 

[Derwud]

Did we get it fixed??