brakes grabbing randomly

I have a 98 Tacoma 4wd 5spd. Everyday at some point while I'm going down the road my brakes will start grabbing some times hard other times lightly. It is so bad I have went through pads in a month. What happens is when they start grabbing I'll keep driving and after a while they will release and once I try to stop the peddle becomes soft and almost goes to the floor but it still will stop like it should. When the breaks do grab the peddle is sort of hard and they will apply with very little peddle move ment. Iv replaced both rubber brake lines and both calipers and still nothing. Iv taken it to local shops and they could not figure it out. Even have had them bleed the system for me thinking it was that but still nothing. Could it be the abs? Is this truck equipped with abs? Could it be the proportioning valve? I am stumped and very mad anything would be helpful. I love the truck but itsabout ready to get shipped if i cant find the problem.

 

Have you removed the pads and tried sliding the calipers back and forth to check for binding. What you describe is a binding condition. Once the brakes bind, they cause the soft pedal from boiling the brake fluid, and the premature wearing of the pads.

If you think it is the abs system, pull the fuse under the hood and drive it, if it continues, it is not the abs system. I honestly don't think that your truck has abs though.

I will venture to say you need new calipers, brackets and complete hardware kits.

 

I'll try removing the fuse if there is one. But I don't think binding is the problem but I will look and see. Both calipers pads pins slides and rubber lines have been replaced.

 

How many miles on the vehicle? Are you located in the rust belt? It has to be binding, abs pump would make it near impossible to drive, if you have it and tried a rapid stop on ice or in the rain, you would know. I say pull everything off down to the spindles and look for shiny spots, slide the calipers thru the brackets with and without pads.
How thick are the rotors, that much wear on the pads, rotors may be too thin and allowing the pistons to come too far out.

 

Truck has 240,000 miles. There is not one spot of rust on the truck anywhere. Its been taken care of. But tomorrow morning I'll strip it down for the 4th time and check what you said out and I'll report back with pictures of what I see.

 

Measure the rotor thickness, you are probably over extending the pistons, they cock and eventually slip back into place.

If everything thing slips back and forth easily, this is probably the best explanation.

 

Any website you think will tell me the thickness.

 

When you changed the pads in the past, did you use the included packet of grease to grease up the caliper slides? If not, your calipers are probably binding.

 

OP, when you remove the rotor, look on the backside of the rotor and either there will be some cast or stamped numbers that will tell you the minimum thickness the rotor should be. Measure in several different spots about 1/2 inch below the top and if the measurement is less than what the minimum tolerance is then toss the rotor.

If you don't have the tools (micrometer) to properly measure the rotor with, then take it to a machine shop or someone that has the ability to measure it for you. If you can't decipher the numbers, then take it to a shop and they can help you out.