Brakes Will Not Stop

[valdezhilander]

When I bought my 83 BJ60 it had a bad vacuum leak in the brake booster. I took it apart and found the piston was broken. My cruiser came with an Asin single diaphragm brake booster. I was never able to locate one or parts for one. I ended up purchasing an early 80's booster for Toyota 1 ton pickups which had about the same size diaphragm and the correct bolt pattern. At the time I also noticed I had a leak from the master cylinder so I went ahead an ordered a new one. I finally got it all together and now I can not get the brakes to firm up. As long as I have vacuum I get a soft pedal until the vacuum is depleted in then the pedal firms up. I have bleed and re-bleed system many times, in fact I flushed all the old fluid out. Does anybody have any suggestions? I've heard the back brakes being out of adjustment can cause this but the parking brake seems to be working.

 

[Doug384]

Adjustment of the rear brake shoes via the adjuster screws may be a cause for the soft pedal. Generally at that age of equipment everything is a mess back in behind the drums. Replacement adjusters may be in order as they often seize tight.

The steel brake lines if they are blocked, pinched or corroded can give the same feel. The rubber flex lines may be flexing too much. Again it is an age related condition.

There is a thread in here to adjust the stroke of the master cylinder piston and rod for optimum operation. There is a specific amount of free play.

Finally, did you bench bleed your master before installing it so that there is no air in it. If it is not done correctly you can pour volumes of brake fluid through it trying to bleed the system not being successful.

 

[David*BJ70]

Did you ‘’primed’’ the brake master on a bench prior to install it?

 

[valdezhilander]

I think I got it. I pulled the rear brakes and everything was free and in relatively good shape. The front shoes were worn so I went ahead and put new shoes on. I put it back together and bled it again. I got some more dirty looking fluid and some air, not a lot, but apparently it was enough because now it's working great. I still need to adjust the parking brake cable, no big deal.