cutter

This one has me scratching my head. Its a 96 sr5 5 speed 4runner with the tundra brakes and tundra/fj80 lift in it. My brakes just started to apply themself after driving for a little bit this morning. Its all 4 as well, not just an individual or front and rears locking up. I can bleed them off and I get my brakes back but I can feel them apply as I drive and not even touching the pedal causes this. I just bled them the other day but have been driving for a couple of days now without a problem until today. The funny thing is they release after sitting for awhile and cooling down. Its like its not relieving the pressure after I release the brake pedal, but it doesn't need the brake pedal to be pressed to cause them to apply. I'm leaning towards having to flush the brake system with new fluid but can't figure out why it happened so suddenly. There was no single instance that caused this other then just driving down the road normally. Could there be an air lock that's not letting the brakes release? Is there a relief valve in the master cylinder that might need to be replaced? and would heat affect it to the point where it would start to slowly apply the brakes? I did a search and haven't found anybody else that's posted this problem yet. Any insight and help would be appreciated. Thanks guys

J2F42C

Does the pedal stay depressed once you let your foot off it? Check to make sure the linkage is not binding.

My grandfather's Chevy Silverado had a similar problem and it turned out the brake booster had failed. I am not sure if it is applicable to your problem. Ever have a hard, hard pedal?

cutter

The linkage is all good, it was one of the first things I checked and as for pedal play, it just stiffens up. The truck is in for an alignment now and I'm feeling lazy, so the shop is going to do the brake fluid flush for me. Hopefully this solves it, otherwise I'm probably going to have to change the brake master cylinder. Not to sure where else to look for potential problems

Sensei

Couple of questions; How do you know all four corners are applying ? Are you sure your calipers are'nt hanging up ?

cutter

I lifted it up when I got to home to check to see what tires were hanging up incase if it was just a caliper hanging up. I just got it back from the brake fluid flush and its still applying the brakes. I was to lazy to bleed the brakes on the way home and when i got out of the truck in the driveway I had smoke coming out of all the wheel wells. whoops
Going to order a master cylinder now, still baffled how it happened on my way to get a coffee this morning. Doesn't make sense

ALLDATAdiy INFO

Have you tested your ABS Relay or Actuator?

Not sure if a decelration sensor would trigger these symptoms at all.