[Sloan66]

I have a 66, all stock power brake system, replaced the master cylinder, and the original booster was rebuilt a couple years ago.

System if fully bled, when I apply brakes the brake pedal does not return, thoughts on what could be causing this? Is it the master cylinder? Booster?

Thanks

[dataway]

Did you eyeball the master cylinder well before you installed it? I guess it could be missing the spring. Did the rebuilt booster ever function properly previously, or is this the first time both were used?

[Sloan66]

booster was working fine prior. I bought a new M/c as I could not find a rebuild kit for my old. So, did not tear into new m/c

[dataway]

I usually take a screwdriver and press in the plunger cup to make sure it moves properly ... takes some effort, there is a pretty strong spring in it.

I've heard of a similar problem with some MC/Booster combos ... I think people solved it by spacing MC from the booster a tad with washers or something. Hopefully someone will chime in.

[Sloan66]

thanks!

[HoovDaddy]

When you bench bled the new master, was the spring pressure strong?

[389]

When it binds up loosen the two nuts on the master cyl and see if it returns.

[Sloan66]

spring was good in master. Yesterday I loosened the m/c from booster to measure rod length and depth of hole in piston. What I found was when I re-installed the m/c and tightened it it was pushing fluid, like the rod was too long. Could this be caused by an internal issue with booster? The booster is OE and was rebuilt a few years back, so I had operational brakes for at one point.

[gtospieg]

If everything used to work and you replaced the master "only" then that is where you should start looking. Do you still have the original master cylinder to compare to the new?

[Sloan66]

Yes, that was my first thought as well, identical to old m/c, same measurements.

[gtospieg]

Well, that is curious. Did you use the booster after it was rebuilt? If so did it work properly? Can you bring the master back and swap for another?

[dataway]

There are short rod combos and long rod. Some repop boosters come with both rods.

I think it depends on how you are mixing and matching Delco and Bendix components.

[tjs72lemans]

I'm not sure if this has an adjustable rod to MC. But, when I replaced a MC on my 55 Chevy, the brakes were dragging. I had to adjust (under dash) the rod back some because it was pushing the MC plunger causing it to not back out and release pressure to brakes.

[dataway]

Good point ... I'd basically loosen everything up MC to booster, booster rod to pedal etc. and see what it does.

I just installed a repop booster on my 68, Deco-Moraine type, and using my original OEM master (Delco-Moraine) and seems to be working fine. Doesn't appear to need any adjustments.

[Lemans64]

Old master is same as new one you say it is but is the hole in back of new master the same depth as original? The hole where the pushrod goes in.

[Sloan66]

All good thoughts, yes I measured depth of hole on replacement master and it was the same as the old one I took off. The booster was the OE that I had rebuilt, I only have one rod that came back with it. I have ordered a new booster to compare. Will be measuring the length of rod, and update all, thanks for everyone's help!

[Sloan66]

The issue was the booster, broken return spring on inside. Thanks for everyone's feedback and ideas.