Brake Peddle Goes to the Floor

[ridinsurf66]

I have a 1999 ford ranger with RABS. My brake peddle goes to the floor. Master cylinder reservoir is full, evidence that there isn't a leak? I replaced the power brake booster with no success. Would it be a safe assumption that my master cylinder is shot?

 

[aspevacek]

I would try the Master Cylinder, remove it from the booster and check around the lower edge to see if you have any seepage there where the push rod pushes the piston on the master cylinder. The other possibility could be internal leak down on the master cylinder. Have you bled the brakes to ensu rethere is no air in the system at all?

 

[ridinsurf66]

I figured after the booster was replaced that the only other part to suspect would be the master cylinder. Thanks.

 

[hondaxr650]

The problem could be with the RABS valve itself. I have had several in the shop that leak internally and bleed off pressure as if you were in an ABS stop. I made a block-off fitting to isolate the valve and rear brakes for diagnosing them.

 

[Vexy]

Are you 100% positive that the brake lines have no air in them? I suspected a bad master cylinder on my truck, turned out to be a large amount of air in the lines. Same symptoms. I'd be sure they are bled properly first before you start spending money replacing everything. Good luck!

 

[diehard80's]

I agree with bleeding them first just to make sure there is no air in the lines. When the master cylinder went bad in my '87 Ranger it would work fine for a few seconds when I pushed the pedal but then it would bleed a little bit of pressure so then i would have to push it down a little further. So with the symptoms yours has, it just goes straight to the floor?