Residual Pressure Valve (RPV)?

[BlissBignall]

First off, does a 74 Thing have any RPVs in the brake system? If so, does anyone know where they may be physically located on the car. I have an on-going issue where the rear brakes slowly tighten up as I drive the car around.

For instance, if I leave the house with, say, 3 inches of brake pedal before the brakes engage, and drive back and forth to work, and maybe around town a bit, I will end up with 1 inch of brake pedal play.

It has been necessary to loosen the brake pedal and adjust the rod back because I was actually having to occasionally bleed the rear brakes just to get home!

Virtually the entire brake system has been replaced (master cylinder, wheel cylinders, rubber lines, pads, drums are in spec), and I'm running out of ideas here.

Thanks in advance.
_________________
1963 Beetle...My mom's car that got sold in 2012
1969 Beetle...That was fun!
1972 Beetle...Never ran right
1974 Thing....Daily driver on sunny days

[Deckard]

I have worked on my Thing brakes since 1992, and I have never seen or heard or a residual pressure valve. It's a very basic system.

[Wildthings]

I would think they would be built into the master cylinder, one for each circuit.

When did your problem start? Had you just done work on the system, particularly the master cylinder?

Ancient brake hoses can make individual brakes pump up.