Brakes building up pressure over time (1 Viewer)

[SlightlyrustyBj40]

Hello everyone new here as a member but have been lurking for a while.
I have a 1978 BJ40 that I have been slowly doing up to put back on the road.
One of the main problems have been the brakes. Still has drums all around. I have replaced all the wheel cylinders, rubber lines, master cylinder and rebuilt the booster. My main problem is I can get good pressure while sitting not driving, but as I drive the brake pedal gets harder and harder to the point that it locks up slightly, with little to no pedal travel. Gets mainly the front brakes real hot. Seams to happen after about 1-2km using brakes a fair bit. Just wondering if anybody has encountered this before and any solutions. I believe I have everything adjusted properly the drums slightly drag on the shoes. Just to add it really seams to mainly affect the left front wheel. Apologies for long message

Cheers

 

[B y r o n]

Have you tried to back off the adjustment on the front brakes?

 

[whitey45]

And make sure you have correct freeplay at the pedal to booster and booster to master. Sound like brakes are dragging and heating up, causing expansion!

 

[45Dougal]

Agree with the above - bleeding them should also help because its the water in the fluid that tends to expand. Brake fluid is hygroscopic so if its not been changed for a while then this can become a problem (push it all through and completely replace it).

Also, since you have a BJ, it's worth checking that your vacuum system is all correct, I.e. vacuum pump on the alternator is working and plumbed up correctly via the vacuum tank.

 

[peesalot]

I recall 2 different residual valve pressures possible your replacement MC has the wrong residual valves, maybe put the ones from old MC in and see.

 

[SlightlyrustyBj40]

And make sure you have correct freeplay at the pedal to booster and booster to master. Sound like brakes are dragging and heating up, causing expansion!

Yep this was the problem.
Took the air filter housing off and the master cylinder and shortened the push rod in the booster
Fixed all of my problems with pressure build up and hot brakes
Thankyou!