FJ60 Brake Nightmare

[ATXCruiser]

Hi guys, I have been reading on this forum for quite a while and I have always been able to find the solution to my problems in other posts, thanks for all of the great advice!

So, I searched high and low all over the site and although I have found issues that partially relate nothing came back as the same issue so here it goes:

1985 FJ60 - All original with the exception of the parts that I have replaced in the last couple of year. I am the 2nd owner and she has about 200k miles.

I recently replaced the brakes, rear shoes, front pads and the rotor and caliper on the passenger side. After I replaced these parts I bleed the brakes and they worked great for about 3 weeks. Just in the last couple of days, the front discs have been locking up, to the point that the truck is emmobile. I let the truck sit for 10-15 minutes and the brakes free up and I can get down the road a ways. Yesterday when this happened the pedal was rock hard and did not want to budge at all whie the brakes were locked. When they released the pedal would travel all the way to the floor with a minor amount of braking power, I bled the brakes again and there is no air in the system.

I checked the MC and the seals look good, I do not believe that it is a booster issue because when the truck is off and I pump the brakes, they get stiff and do not move, but when I turn the truck on, the brakes get soft and go all the way to the floor again.

Any ideas or suggestions would be greatly appreciated!

 

[Wile E Coyote]

First off, welcome to Mud. Secondly, it's generally recommended to replace rotors in pairs. Calipers too, but my opinion is if the old caliper still works within spec then it's not going to matter.

On to your question with a question of my own:
When you bled the brakes, do you remember the pedal going all the way to the floor even once?

 

[tunegoon]

Sounds like a swollen brake line not allowing fluid to bleed off. CHeck your rubber brake lines.

 

[Mace]

You replace the master cylinder as well?

 

[Dallas Cruiser]

I had a similar problem on my 84 FJ60 that had about 240k miles at the time. My brakes were really soft when the rig was cold but after driving to work about 15 miles all 4 brakes were dragging. I am a mechanic so I put it on one of my lifts and I could not turn any of the tires by hand. As it cooled down the brakes started to free up. Before they were totally free I cracked open the brake lines at the master cylinder and then instantly they were free. I replaced the master cylinder and it cured the problem. On a side note right after that I had to replace the proportioning valve due to the seals being swollen internally and causing my rear brakes to not release. All is good now and haven't had a problem in 5k miles.

 

[ATXCruiser]

During the bleeding of the brakes the first time the pedal never made it all the way to the floor, I will check out the MC and see about replacing it.

Being as I am a novice, any advice on what to look at first, steps. Thanks again for the replies!

 

[Godwin]

I'm going along with the others that think it's the MC. I recently went through the brake system on a FJ60 replacing the rear cylinders, front calipers, and all the soft lines. The system was well-bled but the pedal was soft. More bleeding followed to ensure that the lines had no air. Replacing the MC, of unknown mileage and age, cured the problem. Have good brakes now.

 

[rchalmers3]

Before condemning the MC make sure it has a little free play in the pedal rod. A pedal rod adjusted too tight blocks the fluid return passage inside the MC, leaving residual pressure on the brakes after a normal stop. This residual pressure heats the brakes and causes the brakes to lock up.

Rick

 

[VTCDN]

Dio time ..

When it locks up , crack (undo quick 1/4 turn) the lines from the MC, free up ?
There is a method to this. Crack a bleeder till it frees , REPORT here.

If the MC crack dose it , and you replaced the MC , then instead of Cracking it the second time , unbolt the MC from the booster , till it frees , if that works , the pushing rod into the master is not letting the MC piston retract enough.

My penny

VT

 

[ATXCruiser]

Ok, so I replaced the MC over the weekend and the locking problem has been resolved but the brakes are still very spongy and I have very little braking power. I can pump the brakes and get the feel that it should have but as soon as I let off the brake it goes back to the spongy feeling.

The pushing rod seems to be going back in fine and I am at a loss for what else it could be.

 

[1tontoy]

Booster

 

[Spike Strip]

You've got air in the system... Get a BIG bottle of DOT 3 and bleed the whole system. Tap the wheel cylinders and calipers with a mallet as you're bleeding to dislodge any trapped bubbles.

Work your way from the furthest wheel (from the MC, on brake-tube length), to the closest. Then re-bleed the MC.

 

[ATXCruiser]

I will try bleeding the system again. I bled the MC and each brake starting with the right rear, left rear, right front left front order. My questions is, once I bleed the wheels again in order, if I open the lines at the MC to bleed it again won't I get air back into the line, thus needing to bleed the wheels again?

 

[Spike Strip]

Left rear, Rt Rear, Lft front, Rt front ... Go by length of brake tubes, not wheel distance from MC.

If you have to pump the brakes for the pedal to get firm, there is air in the system.