3B II,brake booster in a FJ45

[Buit 78]

After many adjustments still having problems with brakes locking up. Pretty sure it is the old booster which was up graded when 78 front and rear ends were put under the 1965. Disc's all around.
Do I have to much vacuum to the booster? Does it require a release valve of some sort? I read that rebuilds are no longer possible. What could I use as a replacement. One thread suggested a 91 4-Runner booster.
Thanks for any help!
Mark

 

[inkpot]

If the problem is the rears locking up too easy, then you probably don't have a booster problem. You need a proportioning valve added into the rear brake circuit to reduce the pressure so the braking is even with the fronts. This is a common problem/solution on rigs with front and rear disc conversions. Search here in the 40 series forum for it and you will find lots of info. John

 

[Buit 78]

All four wheels seem to get equally hot. I can tell something is happening as my turbo temp starts to rise and you can feel the drag when I push in the clutch. Brake pedal also gets a lot firmer. This all happens after about 10 miles of travel. I stop and bleed off both lines at the master,(2 or 3 drips) and take off the vacuum line and away I go. First I thought the heat from the turbo was causing expansion of the brake fluid in the lines so all were insulated. With the vacuum disconnected I have no problem, just very weak brakes.

 

[inkpot]

Sounds almost like the pushrod from the pedal to the booster is a wee bit too long. When that happens, then the brakes never have all the pressure taken off. The longer you drive, the more the problem. I would try shortening that rod by about 1 turn to see if there is any change. John

 

[Buit 78]

Thanks John for the help,
The MC is new from SOR. I have tried what you suggested, Also I've shortened the shaft from booster to MC as suggested from a friend mechanic. I'll keep playing with the adj. today and see what happens.

 

[Buit 78]

After taking the MC loose from the booster and lots of measuring I took out the adjusting bolt in the shaft, cut off 3mm and replaced it all the way in. Totally I reduced the shaft length about 1/2". Drove aprox. 10 miles and all is well. Brake pedal went to the floor so lengthened the pedal to booster shaft, so now have good brakeing at 1/2 pedal. Hopefully this will do it.

 

[flop]

mine was doing same thing replaced brake hoses solved problem