Brake Master Cylinder Problems/Questions

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Joined
Jan 16, 2006
Threads
66
Messages
185
Location
Altoona, Pa
I have a 1970 FJ40 that has a mini pickup power brake master cylinder/booster on it. It also has a disk brake front axle on it from a 76 FJ40. The brakes have never seemed that strong to me. It would stop but wouldn't lock up the wheels if you really put your foot into it and just didn't seem like it would stop very quickly. On the other hand, I have a 74 FJ40 with 35's on it that stops really well and I believe it has a power brake system from a celica on it. On the master cylinder, the front port has a short line that comes down to what I believe is a proportioning valve mounted on the booster directly below the master. From everything I've read, that should be going to the rear brakes. So this one was connected that the line off the proportioning valve was going to the front brakes and the rear port on the master cylinder was going to the rear. So tonight I switched them so the line off the proportioning was going to the rear and the rear line off the master cylinder was going to the front brakes. When I bled the brakes, I had strong fluid flow to the back brakes but I had very little flow at the front brakes. If you really pushed hard on the pedal you would slowly get flow coming out the bleeder but it wasn't shooting out like the rear was. I then pulled that line off the master cylinder that is going to the front and even there I'm getting very little flow. It seems to me this master cylinder is bad but I wanted to make sure I wasn't missing some other issue. Also would like to confirm I have the brake lines properly connected to the correct port. Thanks for any guidance.
 
I have a 1970 FJ40 that has a mini pickup power brake master cylinder/booster on it. It also has a disk brake front axle on it from a 76 FJ40. The brakes have never seemed that strong to me. It would stop but wouldn't lock up the wheels if you really put your foot into it and just didn't seem like it would stop very quickly. On the other hand, I have a 74 FJ40 with 35's on it that stops really well and I believe it has a power brake system from a celica on it. On the master cylinder, the front port has a short line that comes down to what I believe is a proportioning valve mounted on the booster directly below the master. From everything I've read, that should be going to the rear brakes. So this one was connected that the line off the proportioning valve was going to the front brakes and the rear port on the master cylinder was going to the rear. So tonight I switched them so the line off the proportioning was going to the rear and the rear line off the master cylinder was going to the front brakes. When I bled the brakes, I had strong fluid flow to the back brakes but I had very little flow at the front brakes. If you really pushed hard on the pedal you would slowly get flow coming out the bleeder but it wasn't shooting out like the rear was. I then pulled that line off the master cylinder that is going to the front and even there I'm getting very little flow. It seems to me this master cylinder is bad but I wanted to make sure I wasn't missing some other issue. Also would like to confirm I have the brake lines properly connected to the correct port. Thanks for any guidance.

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Has anyone experienced air in the master cylinder creating this type of an issue? I’ve continued to research this problem and it seems like that could be the problem. It just seems like with the line going to the front wheels removed from the master cylinder, if it was air it would push out and I’d get good fluid flow.
 
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