PLEASE HELP w/ my brake problem

[brent239]

I have a serious brake issue. My parents used my 92 4wd explorer to take a trip to missouri. when they got back we had a problem with the pedal going farther than normal. it turned into the pedal going all the way to the floor before anything would happen. we have since changed the brake booster, master cylinder and checked all brakes for movement and found a slight problem with the right caliper which I got from CRAPzone about 1 1/2 years ago. so I replaced tha because it didn't seem like it was fully compressing. We have since been stumped with this problem. there is no brake fluid leaking, no BRAKE light on inside and dont have a F-EN clue what is causing this. We are gonna try adjusting the brake booster tonight but we'll see what happens. ANY HELP IS MUCH APPRECIATED, I Know I can count on you guys helping me out. Thanks again

 

[Robb]

Was the master cylinder bench bled? Is the movement to the floor spongy, or just straight to the floor?

Robb

 

[Jason_25]

Stupid question:

Were the brakes bled properly?

 

[brent239]

yes the brakes were bled properly, but I hae never heard of something being bench bled. the movement is spongy yes with the truck running. we were thinking about it being a bad master cylinder from the store. we tried adjusting the booster rod that goes into the master cylinder, and nothing happened. thanks for your response

 

[Robb]

If the master cylinder wasn't bench bled before installation, then you have probably got a whole bunch of air in the lines. Therefore it will be spongy.

Robb

 

[brent239]

what is the proper procedure to bench bleed a master cylinder? My stepfather said he heard of it before but was unsure how to do it

 

[Robb]

Instructions should have come with the cylinder, if it was bought new. There may be a proper procedure for it in the Haynes manual, but I am not sure. It's mainly just putting the cylinder in a vise, filling with fluid, and pumping the piston a few times. It simply fills the entire master cylinder with fluid, so no air is left in it, which would go into your lines.

Hope this helps,

Robb

 

[brent239]

ok we did that and found out we had a bad master cylinder. so we changed that one out this morning and bench bled it like you said. then bled the brakes again. it helps somewhat but we are still having a problem with it feeling spongy. the pedal travels farther than it should but at least now it stops the truck. should I just settle with this or is there anything else we can do. one thing is under hard braking the rear passenger tire still locks up. we tried turning up the left one but still does it

 

[Dr.Doug]

Sounds like it could be the RABS assembly. If this has never been changed, suspect this.

Let us know the outcome.

 

[Rscotts1]

Not too sure If this might help or not, but on my last car (Mitsubishi Galant), I had to change the rear calipers'. Simply bleeding them the old fashioned way did not help. The car was equipped with ABS and come to find out that there is a specific procedure as far as bleeding the brakes. Underneath the Mitsu there was some kind of solenoid (in the rear) with numerous zerk fittings that had to be bled sequentially, (specific order) as well as bleeding the proportioning valve. Air can and does get stuck in these places. Hope this helps.

 

[james t]

also, if first master cyl. was never bench bled, then you now have air in the RABS.