1995 4 runner with abs...i have searched threads for 2 days found plenty with same problem but still no solution..front brakes are locking up..replaced master cylinder,brake booster,i have a proportioning valve on way...i had them freed up the other day then drove about 5 minutes and were locked up again,released pressure on brake lines at master cylinder and they freed up,but as soon as i hook line back up pressure builds up and locks them again,it was worked on prior to me buying it im not sure if brake lines are correct going to abs pump they had parts off 96 tacoma,i replaced with 95 4 runner except for abs pump...can i bypass pump and run standard brakes

 

I have this exact same problem. It feels like the pedal is stopping way too short of where it should. Then when I go to slow down quickly it locks the front brakes up. Everyone once in a while it gives and the pedal feels normal for a bit and the front and rear brakes work in harmony, but only for a short period. Do you have any type of lift in your truck? Someone told me it might be because I have an OME 2" lift and it messed with the brake lines. I have dealt with this for a while now and still haven't been able to figure it out.

 

To OP: Are you sure your calipers are not sticking? If the piston is frozen up or hanging it will lock up, you can bypass the ABS by just running brake lines past it and not through the ABS. But typically ABS does not increase pressure, it only cuts it off and reapplies to keep the brakes from locking up, have you adjusted the pedal rod or checked it?

Foskco: When you lifted the truck did you compensate for your LSPV? If not, it is at a different angle and will do funny things, not sure what year of truck you have but if you have the LSPV it will be on the rear axle.

 

Another problem could be the rubber brake lines that go to the calipers. They are usually double wall and sometimes they will collapse inside. It will hold pressure against the brake caliper and not let the pistons in the caliper retract. I have seen this several times. Also as said above, Toyota calipers are known for locking up.
Good luck. Hope this helps some.

 

I dont think the LSVP was adjusted on mine, so that could be it. Unfortunately I dont know much about it. I got some new flex lines for the front brakes to try as well.

 

Just to help out(hopefully), the abs is only on the rear brakes. Now, the lspv could potentially be an issue, even though it's a rear brake system...there's a line that goes to it, then a line that goes back up to the front brakes from it, for some reason. If you're going to be putting in a manual proportioning valve, get rid of the lspv and the extra line going back up to the front. I think I might just change out the soft lines to the calipers first, though, if it were me.

 

Have you checked to see if your truck has a metering valve and if its clogged in some way to adversely affect your front brakes?

 

If releasing pressure at the master releases them, then the problem is in the master.

 

Search my name in the search menu. I had this exact problem and I figured it out. I believe the thread name Is called messed up brakes or sum thing like that. Anyways it's a thread I started and it should explain ur prob and tell u how to fix it

 

1995 models do have 4 wheel ABS.

Have you ran the ABS diagnostics? Do you have a ABS trouble code?

Toyota~Boy's thread, his fix was an adjustment at the pedal push-rod.

This indicates maybe a worn out spring, either the pedal return spring or one of the master cylinder springs, or time to clean and rebuild the MC and flush the fluids.