71 fj40 front brakes locking up

[rugerberetta]

I must be the exception( knock on wood) I have not had any problems with my brakes after a front drum rebuild and new master from ccot.

Whats the back story on this?

Does not appear to be related to the CCOT aftermarket master probably need to continue and finely adjust the length of the booster push rod. That is all that is left to do. I think I will walk away from it for a day or so. Then if I cannot get my adjustment right I think I will punt.

 

[Chugging Along]

FSM says that the pedal height should be around 7.28-7.87 from the floor that's at an angle (the one not parallel to the ground)

The pedal play should be .12'-.35'

What kind of brake fluid are you using?

 

[Rockets2000]

Make sure your brake shoes are adjusted properly. It doesn't take much to get them out of adjustment with new parts. Jack it up, tighten both cylinders on each wheel until the wheel will not rotate, then back them both off 2-3 clicks. Do it cold.

 

[rugerberetta]

FSM says that the pedal height should be around 7.28-7.87 from the floor that's at an angle (the one not parallel to the ground)

The pedal play should be .12'-.35'

What kind of brake fluid are you using?

v DOT 3

 

[rugerberetta]

Make sure your brake shoes are adjusted properly. It doesn't take much to get them out of adjustment with new parts. Jack it up, tighten both cylinders on each wheel until the wheel will not rotate, then back them both off 2-3 clicks. Do it cold.

Had them backed all the way off and still had the issue of them locking up after a few miles. Trying to get this issue resolved them will adjust correctly. Thanks

 

[Chugging Along]

I go back to quoting Toyota FSM the drum new should be 290mm in diameter. Any way to check your drum?

What's throwing the wrench into it for me is that cold mine may have a slight drag but that goes away quickly as I get moving due to expansion.



EDIT: looking into the booster side of things .

Before you bleed the wheel cylinders have you bled the booster at both bleeder plugs? If you do this do not run the engine or have a vacuum in the system

Have you checked for a vacuum leak on the hose.

Inspect the check valve seat for any debris that would stop it from making a seal.

Have you filled the brake booster with oil?

 

[Chugging Along]

Also, try running the FJ with the vacuume line off the booster. Make sure to plug the line. Drive it for the normal amount of time and see if the brakes still seize up. If not the it's the booster.

Remember braking will be alot different with out the booster.

That's all i got...... Be safe and use this advice at your own risk.

 

[rugerberetta]

The factory booster did not have the vacuum valve the new booster does at first I did not hook it up and brakes locked up after a few miles, hooked it up by splitting the vacuum line that feeds the FD system. Notifiable change in the feel of the brakes but no change in locking up issue. I caused another issue while replacing all front lines,I stripped a Tee fitting on the pass wheel so now have to wait until my replacement arrives. Then I get to start the process all over again. Who knows maybe I will install new Tee hook up bleed and all my issues will go away. FAT Chance but one can only hope. If I only had the money to convert to disc. Thanks for all the suggestions I will update once I get my line fixed and brake bled and tested.

 

[rugerberetta]

Well finally got the new lines all in and brakes bled, push rod adjusted and I have brakes but they are weak. I think I need to now adjust my wheel cylinders out. I did go for a short test drive and the front brakes did not lock up or drag and were just barley warn when I got home. The bottom line is I do not know if it was the 40 year old lines or just the booster push rod but I am glad I looked at the lines they were bad meaning just a little movement and some broke in two. Now the whole system in 100% new so after my adjustment tomorrow I should be good to go for awhile. Thanks for all the input.

 

[Chugging Along]

Glad to hear about the positive progress. Interested to see how it developes, please keep us posted!

 

[lcwizard]

That should be the relief port. Duplicate the position of the OEM port with the
same size drill bit. You'll need to disassemble the master

I checked the old master against the new master and the old has a small hole drilled in the very front of the cylinder the new one does not so if this is the relief port then this is my issue I purchased from coolcruisers so I will call them and ask. Thanks

 

[J40Fan]

I had the same problem recently with the front brakes locking up after about 20 miles of driving. I thought it was an adjustment problem at the drum or a bleeding issue. I bled the brakes several times and adjusted the drum per the FSM; The issue persisted. Come to find out after pulling the master cylinder out and disassembling for overhaul, I found the forward seal split, causing fluid to fill the area where the forward spring resides ... that area should only be air. This trapped fluid will not allow the spring to release due to the hydraulic lock. So if you are having brake locking issues to the point the brakes are smoking, look at this possibility.

Also one other issue you may notice for this scenario is the brake pedal is hard at the beginning, and takes very little travel to apply the brakes. As you drive this hardness will increase until it is as solid as a rock, at this point the vehicle can no longer move.