Hey there, I've drove these trucks for the last 20 years so I'm very familiar with how they should drive and feel. I currently drive a 90. My daughter just got her first pickup, a '92 single cab. She called me the other day and said somebody pulled right out in front of her and she had to slam on the brakes and skidded a little. And after that her brake pedal felt weird. I checked it out and sure enough the pedal is really high. The brakes actually feel good with tons of braking power it's just like all the take-up is gone. This has a brand new set of pads on it that I put on a couple months ago.

I jacked it up and spun all four tires and there's not an obvious drag. There's basically no drag in the rear and just the tiniest sound from the front which I would say is pretty much normal from my experience.

I held the brake down while it was running to check for any boost or bleed down and that seemed fine. I also cracked each bleeder on the front calipers just to see if there was any built up pressure for any reason and just got a dribble.

I'm kind of at a loss. My only other theory is I have had some bad brake lines in the past that delaminated on the inside and created a minor check valve. So after you press the brakes it would be really slow to release. But even still I don't see how that could be because it's not really dragging much at all and I don't see how that would change the actual pedal feel. I even looked under the dash to see if something physical happened like the bent bracket or something weird.

Do you guys have any ideas?
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My theory is that something is wrong with the master cylinder. The calipers aren't dragging they feel normal. But l think maybe the master cylinder isn't returning all the way. So all the take-up is gone or something like that. Does this sound like it might make sense?

 

Check the pedal height alignment. If the MC isn't correctly aligned any more it might feel odd. It's possible you pushed the center rod past it's 0 point. Check that the booster doesn't bleed down ny faster than the FSM calls out, and that the one-way valve in the vacuum line is functioning correctly.

Bleed the brakes, which you should every couple years anyway. Make sure no air got in, and that new, clean, fluid is in the system. If the fluid is dark, it has water in it. That can make steam in the lines when braking hard. thus, you now have air bubbles in the system that need to be bled out. All 4 brake lines should be bled until new fluid flows out, and no air, and if you have one, the LSPV is cleaned out as well. It can hold air, as well as crud and corruption. Bleeding the brakes can solve a huge number of problems you wouldn't expect of it.
The sequence is RR, LR, RF, LF, LSPV. Don't neglect the LSPV! It matters.

Good luck!
Pat☺

 

Thanks for the ideas. What do you mean by pushing the rod past its 0 point? Is that like if the pedals push too far down?

 

The FSM for my year suggests :
1)Restricted brake lines
2) oil or grease on linings (don't quite get that one)
3)seized piston in caliper
4) faulty booster or check valve

The one item not listed. The brake master