Anyone know of a source for the Load Sensing Proportioning Valve (the thing for the rear brakes to compensate for loads) besides the dealer? None of the local auto parts stores seem to be able to get them. I can try and find a used one (and I posted an ad in the wanted section) but used brake parts are not ideal.... Because my '85 Toyota 4x4 pickup sits for 6 months out of the year every year, the LSPV seized up on it. I can unbolt the bracket off the rear axle and manually cycle the rod, but it doesn't do much to free it up inside.

I've seen very similar, if not exact, previous posts from other people about these symptoms and figured I could also share my story. People suggested a sticking master cylinder, cracked pedal bracket assembly, loose sticky pistons in the calipers, rusted pistons, or a bent line. Before I realized it was the LSPV, I replaced the brake booster, master cylinder, front calipers, front pads, rear wheel cylinders, and re-bled enough times to fill a 5 gallon bucket.

The symptom was that the brake pedal stiffens up halfway through to where it used to, but I had maybe half the braking power. If I stepped on the pedal hard, then it would "pop" and travel further to it's normal position (but not to the floor). The brakes only seem to half work when I don't step on the pedal hard, but fully work after the pop and the rear engages. I've confirmed this by hitting the brakes on ice and seeing if the rears engage at all. Nope! The fronts lock up. If I unbolt the bracket off the rear axle and tie the rod up to the underside of the box, it brakes normally. It also dawned on me that my front brake pads were not that old and had suddenly worn out quick, and my front wheels would quickly fill up with brake dust on the outside, again pointing to the fact that my front brakes were working overtime. Unfortunately I had already replaced all the previously mentioned components before I finally discovered the real problem.

Now I just need to find a good used one or an aftermarket source. If I remember right, the LSPV is very expensive from the dealer.