flyfishexpert

1998 4Runner SR5
4x4
ABS

To give everybody some background on the situation, at the beginning of the year I was driving down an icy, sloped street and applied my breaks to slow down. Everything seemed fine until the right side of the vehicle traveled over a dry section of pavement. It was at that moment I discovered the right front tire was not rotating, even after I released the break pedal. The tire ended up skidding across the pavement, causing the vehicle to pivot around. After talking it over with a few people, I reached the conclusion that perhaps one of the caliper pistons had seized. I proceeded to replace the front breaks, calipers and all, upgrading to the Tundra setup. This apparently did not solve the problem, and a couple of days later, driving down a similar street, the problem arose again.

Thinking that perhaps it had something to do with the ABS, I removed the fuse and drove around. Still the break locks up and stays locked after I release the pedal. I tried to get the break to lock up on a flat surface, but was not successful. This leads me to believe the problem is related to angle of the vehicle and the level sensing proportioning valve.

Does anybody have a schematic for the break system? I want to know where in the system the level sensing proportioning valve is.

I need help determining the culprit of this problem. Manditory time off with out pay, due to the economy, means I can not go to my mechanic for help. Has anybody experienced anything like this? Any help would be great!!!

Tylercs

This happend on my wifes focus and it was the caliper. But I guy at the parts store said that it could be the rubber brake line he said when the brake fluid gets hot from a long prolonged stop or slowing like going down a hill it can cause the line to balloon restricting the movement of the fluid back after the peddle is released and cause the brake to stay engaged. Then the problem might not show up when everything has cooled down.

I hope that helps but it could be all bogus because he wanted to replace all the lines and was ticked off when I said all change the calipers myself.

flyfishexpert

Calipers have been replaced.
Problem occurs at any time, after little breaking and lots of breaking. Seems like mostly happens when traveling down a decline with ice. (Actually noticed it happen on decline with gravel covered pavement too)

flyfishexpert

Bump for a little help!

Yukon

you bleed the whole system? maybe a master cylinder

flyfishexpert

I have only bled the front, but I don't see how air in the line would cause the caliper to lock. Air in the lines would cause the system to spongy, right?

I have thought about the master cylinder, but I think it only happens when going down a slope causes me to think it is the LSPV.

scotch

I believe abs equipped 4runners do not have the proportioning valve. At lease my 97 doesn't.... I just completed the tundra brakes on both my vehicles, and have an extra master cylinder if you want it. I have both styles. Which calipers did you install? The 13WL requires a little grinding to clear the stock wheels...

flyfishexpert

I traced all of the break lines and did discover there is no proportioning valve.

I ended up installing the 13WE calipers so I would not have to grind the wheels.

I am going to replace the flexible line on that side to see if it is damaged and causing the problem. We will see what happens.

northfacer581

dude im having the EXACT same problem. however mine is happening more than just declines, it really happens quite a bit more, especially when im coming from 5mph to a stop if i do it somewhat fast instead of very slowly. i thought it was simply because i havent had my pads or rotors checked in a while, and they (dealership) replaced both up front, but it still happens.

please let me know what you find out. best of luck with it.

darksoldier313

first thing that comes to mind is a clogged line somewhere from the master to the caliper usually its the brake hose directly on the caliper however metal brakelines do rust and build up inside my suggestion would be to break open the bleeder on the side that locks if fluid drips freely thats not your problem if it doesnt id check the lines replace and flush the system

holskey

if im right it could be the brake line..... i had the same problem on a camaro. what happens is the rubber inside the line swells and it cant release the piston... the fluid can still go into the caliper but b/c the swelling it cant get back out. try replacing your lines.

holskey

sorry should have said..... check for fluid drip like (darksoldier) said.

flyfishexpert

I have narrowed down the proble to the ABS actuator. There is no abstruction in the line because I can bleed the system fine and fluid drips out when the lines are disconnected. The only other component in the system that it could be is the ABS actuator. The actuator has a series of valves that relieve the pressure in an indevidual line and then reaplies the preasure with a small pump. I am thinking the valves for that wheel are bad. I will be calling around to get the price on a used actuator from an auto salvage lot.

Andy,
Is your problem on the same side as mine? Right Front?

knucklehead38401

Any updates on this? I'm having the same problem on a 97. I replaced both calipers, rubber lines, rotors and pads. I haven't tried a master cylinder yet, that is the next thing and I'm going to reverse bleed the system and change fluid.

flyfishexpert

I have since replaced the ABS actuator with a used one from a salvage yard, but the problem still persists.

Because the problem only happens on the right front side, it leads me to believe the problem is not with the master cylinder. My next step will be removing the hard lines from the ABS actuator to the rubber lines on that side. About half the way down, there is a small block where the line from the actuator meets the line connected to the rubber line. I now have a feeling the problem lies there. We will see.

Crux

Did you ever figure out where the problem was?

knucklehead38401

I got another new master cylinder and it fixed the problem, I guess I must have got a bad one the first time.