Brakes hanging when hot (?)

I have my booster pushrod adjusted back so I have a good amount of travel to the pedal and good stopping effort - when the car is cold. After heat gets into the brakes the pedal travel changes and the brakes don't release as readily.

After I have driven the car for awhile, the amount of pedal travel I get is reduced and the front brakes won't pull back all the way if I'm poking at the brakes a lot vs doing higher-speed stops (in traffic or in parking lots vs dropping 20mph on the highway for example).

They don't drag per se, but they will sometimes stick just enough to keep the car from rolling under its own weight at first or even just enough to *skee skee skee skee* a little until I go faster. They retract enough for the car to roll normally after I get going but not when I let off of the pedal initially.

They aren't smoking or locking up or anything but it is annoying. Every time I drive the car dead cold it's the same thing - full travel and release but eventually the pedal comes up some. I have tried stomping on it repeatedly in the driveway and I get a little of the travel back. I have backed the pushrod off around 1/8" from where I started and my "cold" pedal travel changed, but the "hot n slow" travel was never a whole lot different.

I know the tolerances in the drums especially will drop as the system heats up, but I expected to be able to compensate for this by moving the pushrod back, not continually get the same issue.

I didn't get this behavior when I was using manual brakes (same hydraulic components aside from the MC). It feels like the MC isn't able to spring back fully when the system is hot vs cold.

I'm wondering if the check valve might be going funky when it gets hot. Where should I look first?

Replace your rubber brake line flex hoses.
Sounds like they are internally collapsed.

So on the hydraulics,only the master changed? Can you put the manual master back and see what happens?

Of course the old crack the line loose can tell alot too.

Fwiw a new master isn't necessarily a good master

booster/check valve issue. shoes hanging up. collapsing hose issue. MC. booster linkage hanging up. holler what it ends up being

If you wait until they're locked up, then loosen the mounting bolts on the master (so the pushrod gap goes huge) and the brakes are still tight, I would look at the soft lines.

For that you can crack a bleeder at the wheel to see if that wheel suddenly frees up (or not).

I have a feeling it's the flex lines, they're the only part I haven't directly tested yet - I'll give this a try tomorrow. The pushrod gap has grown a comparative great deal since when I started chasing this problem and the light duty brake behavior hasn't changed hardly at all.

After leaving it overnight with the problem happening, I tried pushing it in neutral with the engine off - pads on the calipers. Jabbing the pedal didn't change it, pulling the check valve out of the booster, pulling the MC out of the booster - still dragged.

I started it briefly yesterday to reset the booster and today I had a free roll in neutral - after I pressed the pedal (engine off) enough to seat the pads again, they wanted to drag.

Anyone know offhand what vehicles/part numbers would get me a 15"-ish long hose with a 10mm banjo fitting?

My current hoses I got as part of a kit from Dr Diff, but I would rather grab something from a parts house in case I have to do a shrug-n-return. I have looked for a few different 80s GM trucks and cars but they're either too short or have the wrong size frame-end fitting.

sounds like a problem i had when i first got my '72 Challenger. drums all the way around. someone put the wrong M/C on the car and the brakes kept locking up. i'd crack the wheel cylinder bleeders and fluid would shoot out and the brakes would release. the correct M/C solved the problem.

Disc brakes do drag a slightly. Just enough to keep it from free spinning the wheel if you have it jacked up. It will turn and you get a slight drag when you try to spin the wheel. Not like drum brakes that back completely off.

I know but this is enough to keep the car from rolling when it's in drive sometimes. When I'm rolling it with it off it still drags much more than any of my other cars.

You don't have an all drum M/C do you? I'm wondering if there is a residual pressure valve in the rear portion of the M/C.

I had a LF caliper that had way too much drag. I replaced it with a parts house $20 rebuilt caliper & it had the normal amt of drag. All good. EDIT If you crack the front caliper bleeders & it frees up then it has to be the calipers themselves as everything upstream is out of the picture

You might want to read the following post paying particular attention to the M/C pushrod adjustment. Your issue sounds like a candidate for the pushrod being too long

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2115445/1.html

This is an MC for a GM truck with the same brake system as me (2.6-2.7" front caliper pistons, same caliper type, and 15/16" rear wheel cylinders). I have a separate small residual valve in the rear circuit for the drums.

Again, I started out with the booster pushrod a good quarter inch or so out and now it's screwed all the way in to the booster. I have some plain dead travel when cold but it comes up the same once the car is hot. It is not a pushrod length issue.

If I have partially collapsing hoses, wouldn't cracking the bleeder release the caliper? Or are they acting like when you put your thumb over a drinking straw?

Also it looks like Camaro hoses will do me right: http://www.oreillyauto.com/site/c/detail...word=brake+hose

yes if it is a pressure problem but if there is a problem within the caliper itself (pads sticking/hanging up/caliper not free sliding on the V grooves) then no