About mid-day during a wheeling trip, I noticed my brakes weren't working so well - had to push it almost to the floor to stop. Still stops but like the first 25-30%.
Originally thought it was "brake fade" from excess use, but it never got better.

Its not super-spongy or anything, just kind of weak for the first bit then firms up, but not until almost at the floor. If I pump it a few times rapidly, it dosn't get any better.

I've bled them a few times (not expecting much) and it's no better. No signs of leaks anywhere. All the soft lines have been recently converted to SS flex. it DOES hold pressure if I press and hold it.

I'm thinking maybe one of the internal seals in the master has gone bad. Thoughts?

 

when is the last time you replaced the rear shoes and adjusters? Also does your ebrake handle come out further then usual?

 

^^^ what he said.
If that's not it, my money is on the master cylinder being shot. My brakes feel the same way and I've replaced everthing but the booster and hard lines.

 

Oh and I have learned the hard way there is no SELF in self adjusting drum brakes on our trucks either. Even with new freshly greased adjusters. lol.

 

Soo.... I took the rear drums off and gave everything a good look over. Shoes have about 1/3-1/2 the thickness left (I have another set on hand). Inside of one (P side) was fairly dirty, that one was missing the rubber cover on the backside, I brake-kleened it pretty well. Other side wasn't so bad.
Not sure how I'd "know" the adjuster's not working, besides just trying the back-up/slam brakes method. I guess it wouldn't hurt to spend some time trying the auto-adjust w/ the e-brake?

 

Just to confirm if its the problem, manually adjust the drum shoes until they are 0.6mm (0.024") running clearance. After the adjustment, check how the brakes feel. If no change then move on to something else.

Does the pedal slowly move to the floor if you hold constant pressure?

 

Stupid question; have you checked your brake fluid level?

 

There are no stupid questions!
Only stupid people!
But since I don't know you I won't assume that...

Fluid is good, been flushed twice.

Played with it last night. The drums are already ever-so-slightly dragging on the shoes (can hear it when they rotate) so they are definitely close.
I did the "pull the e-brake 1,000 times" thing. The e-brake tension definitely got better. So that is adjusting. Brake feel is a bit better now but still not great or as good as it has been.
Also going to try disconnecting the LSPV and tying it upwards, to see if that changes the bias any, w/ my lift it's really angled downward. That's not new, been like that awhile so it shouldn't "fix" anything but may tell if the LSVP is doing its job at least. I plan to ditch it for a fixed one anyway.

Holding the pedal down does not obviously lose pressure. It may lose a little, but not a whole bunch if any.

 

Re-reading this post, I would look at this for a minute. How recent? In the world of brakes the best question to ask is "what was changed?" just before your problem occurred. Given that you have bled your brakes recently, I would try an old Indian trick:

1. Push the pedal so that it hold a fairly high pressure.
2. Somehow secure the brake pedal in place (rod/2x4/whatever btwn the pedal and the seat brackets for example)
3. Tap on the calipers and wheel cylinders with a plastic, rubber, or rawhide hammer and in your case move around your new SS lines.
4. Walk away.
5. Tomorrow, tap stuff again
6. Remove the rod and gently release the brake pedal.
7. Check how they feel

More times than not with autos and 100% on motorcycles, this has worked for me to fix 'rogue' air and a soft initial pedal due to it. The high pressure compresses the air bubbles and allows them to move.

Free and easy!

Good luck.