very puzzling brake problem...

[parabola]

and you were driving this fast on the track or through downtown Pflugerville?

I no longer do stupid things like that on public roads.

 

[Cobra Jet]

I have this same problem on my '86 mini truck. I've been fighting it for years. The pedal is mushy and soft but will NOT pump up and will not allow for brake lock up and will go to the floor under meduim foot effort. It really feels like there is a leak in the system, but there is none. The pedal feels this way the moment the truck is cranked, so there is no possible way it is boiling fluid.

So far I've ruled out Master Cylinder, Booster, Calipers, Slave cylinders. Just to note, I have stainless steel lines and in NO way could the old rubber lines flexed enough to cause a soft pedal, so SS lines is no where near a fix for this problem. They only thing I can think of is that the LSPV is some how bleeding off pressure and not allowing the full use of EITHER front or rear brakes. I have taken a LSPV apart and there isn't much to them, a few rubber o-rings, one spring and thats about it. I'm down to replacing the LSPV and if that doesn't fix it I have no clue.

Can you please tell me what the acronym "LSPV" relates to???

 

[landtank]

Load Sensing Proportioning Valve


And how does a vacuum problem translate to MUSHY brakes. I can see a change in effort or even not allowing any pedal movement at all, but mushy.

 

[landtank]

Another thought on your problem:

While the front calipers are a 4 piston unit the rear are not. The rear is a typical single piston where the caliper needs to slide on pins to clamp the rotor. I've had these pins seize up and restrict the calipers movement. When this happens you are basicall only pressing on pad against the rotor and then flexing the rotor under more pressure, giving a mushy feel.


I'd pull the rear pads and compare the inside to outside thickness. To just drop in pads you don't need to pull the caliper so some pin binding might be present.

 

[drexx]

23Jul2005 (UTC +8)

After so many helpful hints from this forum, I think we finally found the solution... but then again, it's too early to really tell. We poured over my Toyota USA factory manuals, until we came to the specs for brake pedal free play. The requirement is between 3mm to 6mm, but we had 15mm! So we set it at 6mm, checked the whole brake system for leaks, then bled the system again, and now it seems to work like it was a new car!

I'm still only 90% convinced that this is the true solution, for I haven't tested in on a long trip yet, and also because adjusting the brake pedal freeplay was too simple and cheap a solution to be for real... but it does seem to be...

I'll keep you all posted, reporting later the tips you gave and what we tested and their individual results, but only when I'm a little more satisfied that I didn't just "hide" the problem. Thanks y'all!

 

[archie]

Mt pulag trip

Here's a pic from mt. Pulag when I went in March 2005. I thought I would see you there with the Landcruiser club of the Philippines. I went to Pinatubo and a Batangas beach with them also. Nice to here that you got the problem hopefully fixed.