Help all new brakes no power assist!

[70 GRAN CPE]

I just rebuilt my front calipers, new front pads, new master cylinder, new rear drum wheel cylinders and shoes. flushed all brake lines, took booster off cleaned it and painted it that's all, worked before I removed it. When I got it all back together bench bled cylinder, bled all brakes replaced all brake hoses, no leaks, brakes have no power assist, I have vacuum to booster, I also re-installed my original master cylinder, feels exactly the same. The only thing I think it can be is the booster could it go bad in just a couple of months, like I said all I did was paint it and let it set until re-assembly. I really don't want to R&R that booster again?? Any feedback would be appreciated. I know the obvious. Car is !970 Gran Coupe I am 2nd owner it's not a put together car. Thanks!

 

[Adam]

Check and see if the booster will hold a vacuum....

 

[70 GRAN CPE]

How never done it.

 

[70 GRAN CPE]

Has very hard pedal with or without car running, will barely stop, doesn't feel like there is any fluid pressure at all, pedal pumps up without car running, but when started pedal goes down far and gets hard.

 

[Adam]

Get a vacuum pump (http://www.harborfreight.com/mityvac-vacuum-pump-39522.html) make sure the connections are tight and see if you can even get some vacuum; if you can, see if it holds or leaks down right away..

Also, make sure the rod in the back of the Master/ pedal is properly adjusted to allow it to return. If the rod does not allow the piston to come all the way back, the piston cannot pick up more fluid..

 

[70 GRAN CPE]

Thanks, I will do it appreciate the feedback.

 

[70 GRAN CPE]

The booster holds vacuum, re-checked the pushrod it is right, booster Dewey said to put plugs in master cylinder ports and make sure it holds firm, doing that tomorrow, If it holds I'm stumped. I said before both master cylinders were tried and re-acted the same so I think they are both ok.

 

[BoomerSoonerVA]

Did you figure anything out? I am having the same problem. With mine they stop the car in neutral but won't in drive. No air in the system.

 

[challenger6pak]

Have either of you done a vaccum test to the motor? Boomer your vaccum may be higher in neutral since the car idles at a higher RPM. Are the booster check valves working?

 

[BoomerSoonerVA]

Have either of you done a vaccum test to the motor? Boomer your vaccum may be higher in neutral since the car idles at a higher RPM. Are the booster check valves working?

I have not yet. Car is in paint once its back I will. Its a brand new booster

 

[Chryco Psycho]

the check valve has to hold vacuum in the booster , this way the engine will build up vacuum & Assist the brakes when applied , if the vacuum is not retained you will have very little assist . Engines with 10" or less vacuum do not make enough vacuum to make the brakes work properly so you need a vacuum pump to increase vacuum .
A better solution is hydro boost connected to the power steering pump this had no dependency on the engine vacuum to work , as long as the engine is running you will have pressure assist

 

[moparleo]

70 GRAN CPE regardless of the booster working, the brake pedal should not pump up. There is still air in system or the rear drum brakes are not adjusted properly. Re check rear brake adjustment. If too loose, the pedal will pump up due to the brake shoes having to open up too far.

 

[70 GRAN CPE]

I re-bled the brakes readjusted the rears, put in new check valve and grommet in booster, have 12lbs vaccum at idle. Brakes do work and have power assist, but not enough. It is either a weak booster or low vacuum, if I'm driving and put in neutral rev it up I have more power assist, but still Iffy on panic stop won't lock em up. I think I will send the booster to Dewey? I did not change the cam same vaccum as before no leaks. Just don't have power like before.

 

[moparleo]

Did you resurface or replace the front rotors ? What type of pads did it have before and did you replace them with the same type ? Semi-metallic pads are hard to stop unless they are hot. New pads needs to be burnished to get maximum brake friction.

 

[70 GRAN CPE]

I did use semi-metallic Raybestos pads, you might have it moparleo I just installed the pads did not turn rotors just checked them for runout I didn't think about not doing those procedures could have that much of an effect on stopping.

 

[moparleo]

If you don't break the pads in correctly, you might hit someone.
http://www.brakeandfrontend.com/tech-tip-brake-burnishing-procedures-for-new-brake-pads-or-shoes/