I recently bought a 83 4x4. With the motor OFF i pump the brakes and they dont tighten, i can just keep pumping with no change in pressure. I bled the sydtem and replaced the booster. I also checked the check valve in the vacum line on the booster. Does anyone have any ideas?? The brakes work but not very well. Thanks

 

Are you trying to say it has a mushy pedal?. Have you adjusted rear brakes?. Did you bench bleed master cylinder when you changed booster?

 

I didnt take any lines loose when i did the BB. I adjusted rear brakes and bled the system. Like I said the pedal will not tighten up. With the motor off you can just keep pumping the brakes and they never change or get harder to push. Every car i have had if you pump the brakes with the car off they get harder each time you press the pedal. When driving and slam on the brakes they just slowly bring you to a stop.

 

Ok, so for right now forget about the funky pedal with motor off. What do you mean the brakes work but not very well? Do you have to pump the pedal?. Do you have to press harder on pedal?. Need more info.

 

So if you had a bad booster, when the engine is running, the pedal will be very stiff. It sounds like the problems you are having are hydraulic problems.
Try bleeding the brakes again and see if they will gravity bleed, it may possibly be a bad master cylinder.

 

Maybe the master is bypassing internally? With old, worn-out masters the cylinder walls can wear out allowing fluid to bypass the piston.

 

Sounds like master cylinder to me as well. The plunger is not holding pressure. Assuming everything is bled right.