This is a long saga. 1998 f150 4x4 with 4 wheel abs and cruise. Installed new rear shoes and drums 3 weeks ago, stoping AOK. 2 weeks ago master cylinder starts bypassing, sometimes pedal went half way to floor, sometimes allway to floor. Installed new master cyl., bench bled before installing, bled out all old fluid and air in system. Stoping AOK. This week if you apply brakes while in a tite turn pedal drops half way,feelslike front brakes are not working, and rear brakes lock up. What the heck is going on?

 

I would try disconnecting the ABS module and see if you have the same problem.

 

you say it only happens in a tight turn... have you checked your front brake hoses? Perhaps one of them is loose or something and a tight turn causes it to leak (not sure why it wouldn't always leak... theres a lot of pressure there). If one of the wheels leaked, it would be a half system failure and you would have the pedal drop half way.

Oh - and on most front-rear split vehicles, there is a mechanism in place to detect a front system (primary) failure and dump all the pressure to the rear (secondary) brakes. Under normal use, there is a proportioning valve that reduces the pressure to the rear wheels because they have less weight on them. Once the front brakes fail, you want all the pressure you can get.

That would explain why the rear brakes lock up on you.

 

I highly highly doubt it is the ABS module - there is no way that an ABS error (short of an external leak at the module) can give you a half system failure.

 

Check the front break lines. When you installed the new pads you may have twisted the lines when putting the caliper back on. Then when your making a sharp turn its binding the brake line.

Ive done this before is why Im saying it. :o

 

I was on my way to work this morn, two blocks from home, first stop sign. Pedal went half way down,rear brakes on verg of locking up. Looked all under truck and at master, not looseing any fluid. Truck was fine rest of way to work and home. Just rebled system, no air. Going out to test drive now.