63 Tbird brake pedal not returning

[63bluebird]

so, here is where i am at currently. have a 63 t bird that the brake pedal wasnt releasing. so, we replaced the master cyclinder and Brake booster. and its even worse now. before the brakes were just dragging after being pressed and then would release themselves after a second or two. but now you have to physcially pull the pedal back to get the brakes to unlock. the car is undriveable as it is like this and need some help figuring this one out. thank you in advance

[63bluebird]

we have also gone thru the linkage, had everything apart, cleaned and greased.

[MN63Tbird]

63bluebird

Two things that help in returning the pedal on drum brakes. The primary one is the springs on the shoes. Have you replaced the springs and wheel cylinders? Also make sure there is good lube on the brake shoe points that contact the backing plate. I would focus on the front brakes first since they do more of the braking. The second thing is you need the vacuum on the booster to be working properly. If you replaced the booster did you also replace the vacuum check valve on the booster? I believe there are 2 designs a threaded one and a non threaded one for 63s. That was an issue of my 63 for good pedal return until I found a good replacement and made sure it had a good seal to the booster.

MN63

[63bluebird]

63bluebird

Two things that help in returning the pedal on drum brakes. The primary one is the springs on the shoes. Have you replaced the springs and wheel cylinders? Also make sure there is good lube on the brake shoe points that contact the backing plate. I would focus on the front brakes first since they do more of the braking. The second thing is you need the vacuum on the booster to be working properly. If you replaced the booster did you also replace the vacuum check valve on the booster? I believe there are 2 designs a threaded one and a non threaded one for 63s. That was an issue of my 63 for good pedal return until I found a good replacement and made sure it had a good seal to the booster.

MN63

have not looked at the brakes themselves yet. like i mentioned, prior to replacing MC and booster they were just dragging a bit. and now they are locking up. we had adjusted them before replacing the parts. do you think they are adjusted too tight maybe? as far as the vacuum check valve, yes it was replaced too. i did try the old one as well. neither one seem to make a difference. the brakes do the same thing whether the engine is running or not...press the pedal and you have to physically pick the pedal back up. and when you lift the pedal back up you can feel the tension on it.

[Joe Johnston]

Possibly the rubber hoses in the system have deteriorated internally and not allowing fluid to freely return after pedal is released. Change all 3 rubber hoses to be sure. Easy and peace of mind if nothing else.

[63bluebird]

to try and isolate where the issue is can i disconnect the master cylinder from the booster to see if the pedal returns with the engine running? i will not be taking the lines off the MC, just removing the MC from the booster. ??? just now i adjusted the brakes to make sure it wasnt the adjustment. i pressed the pedal so the brakes would lock up like they have been doing then lifted the vehicle on the lift and backed off the adjusters until the wheels came free. this did nothing to help, the pedal still does not return after you take your foot off the pedal. well, let me be more specific...after you take your foot off the brake pedal there is some slack in the pedal, the pedal itself is free, but you have to physically pull the pedal back to get the brakes to release. i did check the vacuum coming from the engine and it appears to be sufficient. i did not put a gauge on it, but there is definately good vacuum on the line to the booster

[ricklove]

Possibly the rubber hoses in the system have deteriorated internally and not allowing fluid to freely return after pedal is released. Change all 3 rubber hoses to be sure. Easy and peace of mind if nothing else.

One hose on each front wheel; but where is the "3rd" rubber hose? Thanks!!!

[63bluebird]

i unmounted the MC from the booster. here is where i am at now. with the MC disconnected from the booster without the engine running the pedal returns on its own. with the engine running the pedal will not return on its own. help??

[Joe Johnston]

One hose on each front wheel; but where is the "3rd" rubber hose? Thanks!!!

On rear axle connecting the fixed steel lines.

[ricklove]

One hose on each front wheel; but where is the "3rd" rubber hose? Thanks!!!

On rear axle connecting the fixed steel lines.

Found it; thank you!!!

[63bluebird]

ok,update time. i started at ground zero. took the MC off and bench bled it to make sure. the piston returns on it own. with MC off the vehicle, engine running, the booster returns on its own. installed the MC and put solid plugs in the line ports. with engine running the brake pedal functions properly. as soon as i start adding lines to the MC the brake pedal wont return. this is very odd. any suggestions? could it simply just need bled again? when we bled it before, after installing the new MC originally we just bled it by cracking the line at the MC.

[Cliff Rankin]

I have read the post several times and not quite understanding. A bad booster will suck the peddle to the floor. If the car is not running and the peddle is down does it come up if you crack the lines at the master cylinder?
Or how does it act if you take off the vacuum line ? The peddle would be a little difficult and hard but it should brake and release.

[Karl]

G'day.
I am not familiar with problems with the brake booster however there is a adjustment with the bolt that goes from the back of the pedal into the booster. This is mentioned in the workshop manual.
Maybe this needs to be adjusted.
Karl.

[RedBird64]

A rubber brake line can fail internally and have a piece of its liner break loose and act like a check valve.

Scott

[MN63Tbird]

Did you inspect and thoroughly clean the control valve in the booster? If it sticks in the activated position it will maintain a vacuum on the MC side with atmospheric on the upside and pull the pedal down when you turn the engine on. After you release your foot from the pedal it is suppose to shift to all atmospheric pressure on the downside and vacuum on the upside retuning the pedal

Mn63