I'm having an interesting problem with my '97 XLT. To start with I've replaced the Master Cylinder and Brake Booster and checked the pads. The pads are somewhat worn but not nearly enough to warrant replacing. I've bled the brakes several times and am still having the following problem.

The brake pedal is/was soft so I do the "adjust brake booster pin" as prescribed by many YouTube videos. I turn pin until I think it's enough, usually about a half to three quarter turn and then test drive and then adjust accordingly. It's all good for a few days and then suddenly it's seems the next time I drive my truck my brake pedal is either very tight or very loose so I repeat the pin adjustment procedure again and still it happens again and again. At first I thought the brakes were somehow self adjusting (sometimes you think strange **** when things aren't working) and that it wasn't working right but obviously that's not possible 'cause they don't self adjust. LOL Then I though somehow the pin in the brake booster wasn't staying in it's adjusted position (length wise) but there is no way to lock it that I know of. All I can't say now is I'm starting to believe there's a ghost in my freaking truck. Any help would be greatly appreciated!

Thanks in advance.

 

Have someone step hard on the brake pedal while you look under the truck. I bet the front rubber brake hoses are ballooning. This is a common issue on these trucks when they get old.

 

Glc, I'll take a look tomorrow but thinking if that would the problem wouldn't the softness be consistant? Another thing I failed to mention in my original post was that the pedal also seems to be very soft when first starting the truck. It's almost like they somehow get pump up somewhat when the truck is running?

 

Did you bench bleed the master cylinder before installing it?

 

Honestly, I did not but have bled the brakes several times since installation. Had the same problem again this morning where when I drove the truck about 8 miles the pedal was fine. The truck then set for about an hour and when I started it back up the pedal was so tight that pads were dragging. I've since bled the breaks yet again and without adjusting the booster pin the pedal softened considerably.

The lines appear to all be in good order so now I'll drive it for a couple more days and report back.

Thanks for you help!

 

The rubber brake hoses on these trucks rot from the inside out. They can impede brake fluid from entering the caliper or from leaving. I have replaced every single one on my truck front to back. If yours are original I would start there.

 

Without bench bleeding the master cylinder, no matter how much conventional bleeding you do, there's always the possibility of some air still being in the system.

 

What glc said. It will take forever and a day to bleed the system at the wheels if you didn't fully bleed the MC when you installed it.