I installed a new master cylinder a few weeks ago and bled all brakes, it has been fine til today drivin home from work, it is trying to lock the brakes up but isn't and the peddle moves intensly back and forth, My "ANTI-LOCK" light has been on since i bought the truck 6 months ago, It does not do it every time i stop but most the time, and at 60mph it is SCARRY hitting the breakes the whole truck shakes. ANY thoughts on this?
Thanks, Kyle

 

What prompted you to change the master cylinder? If you pull the sensor on the rear axle, is it covered in metal shavings? I have been there done that with these brakes and usually it is the RABS valve, but this sounds like the sensor is doing odd things.

 

Oh my rear adjuster for the drum brake came off and i fixed it 3 weeks ago and that is not the problem now and my peddle went to the floor and so it thought that the master cylindar went away but it didn't but there is nothing wrong there that i know of, Can the RABS sensor in the rear end be the problem???? I am probably gonna take it the the brake shop tommoro and then ill have them take a look and turn my drums and put new shoes on cause its due.

 

I would start by adjusting the rear brakes by hand and disconnecting all the RWAL plugs (start with the one behind the glovebox)..also check the /4" vacuum line running from the brake booster..this should firm up the pedal a bit...if not, try bleeding them againn, I hav found it usually take a few times....good luck

 

My peddle is really stiff and i adjusted the rear brakes last night and still the same thing, ill see what the brake shop says today. they work great sometimes and other times are scarry.

 

Disconnecting the Abs controller and performing a stomp test is a good preliminary evaluation..Are the front or the rear brakes trying to lock? Which lock first?

 

Problem fixed!!! The automatic adjuster lever came off and got between the drum and the shoe which was causing it to lock up from time to time, I wasn't cheap this time and i bought all new hardware and shoes which seems to be right on. Thanks for the responses,