Brakes Brakes drag when warm. How to diagnose?

[FastDriver]

Guys, since the Cobra Brake swap on Black Jack, the brakes drag only after driving for a decent amount of time... maybe 20 minutes of driving.

I've jacked the car up after getting home from such a drive, spun the tires on all 4 corners, and it seems to be coming from the fronts on both sides. The rears are a little less clear, as I have to turn the axles with the wheels and can't tell for sure if it's brakes. They also don't drag when cold. I can tell when driving because when coming to a red light, I'll slow to ~3-5mph and let it coast to a stop. When I've just started driving for the day, I can't feel a sudden stop when coasting to a stop; it just gradually stops with any sudden end. Later, though, presumably after they're warm, it comes to a more sudden stop at the very end... kinda hard to describe.

I've adjusted the plunger between the booster and the master cylinder to the point that the pedal depresses a bit before engaging. I've also, suspecting the e-brake cable, jacked the car up when cold and spun the rear without any drag, seemingly.

Anyways, does anyone have any ideas of what I might check to diagnose things?

 

[AeroCoupe]

In there any possibly the brake fluid is heating up and expanding? Would be from the exhaust being too owe to one of the lines.

 

[FastDriver]

Good thought. I'll take a look.

 

[qikgts]

Dovetailing to AeroCoupe... Brake hoses often swell on the inside and can restrict flow, that potentially could cause the calipers to stay engaged. If the hoses are old may be cheap insurance and a solution all in one.

 

[90sickfox]

To check if it is a hose, prop valve, or master just drive the car until brakes are hot and dragging. Jack it up amd make sure the wheel is hard to spin and then crack the bleeder on the caliper. If brakes free upits a restriction in the path or residual pressure.

I have no faith in aftermarket brake pads lately. I've had several sets that have needed filing in order to move freely. Pads should easily slide back and forth in the brakets. If they are too tight the metal will expand and cause your type of issue. If they are too loose it can cause a click when using the brakes.

 

[FastDriver]

All the hoses are new with my swap to the Cobra brakes. At first, I didn't think cracking a bleeder would tell me much, but that would be to differentiate between it being bad pads/sliders or pressure.

Never heard of that one. Thanks, @90sickfox

A friend threw another idea at me to check, too. I have that MM kit to completely get rid of the plugged stock prop valve. Not sure exactly how it could be holding pressure in, but can't hurt to get rid of it.

 

[Mustang5L5]

The passages in the combo valve corrode and get blocked and can act like a check valve. I've seen it happen

 

[FastDriver]

combo valve = stock prop valve?

I've got the MM adapter to remove it.

 

[Mustang5L5]

Yeah. It's technically a combination valve. The proportioning valve is in the front, and a shuttle valve is in the rear.

 

[Ybfav84]

combo valve = stock prop valve?

I've got the MM adapter to remove it.

Did you figure it out? I’m having the same problem

 

[FastDriver]

Still dealing with something, there. There were two things happening, at least. The emergency brake cable was causing drag. When it snapped, that cleared up that problem. I need someone who can weld to fix the ebrake handle and tack in the correct threaded manual adjustment adapter.

The other problem is still unclear to me, and it does intermittently drag, as well as I can hear it pop when it shifts as I transition forwards to backwards and vice versa. I'm planning to pull the calipers off and take a look and possibly replace with some old Baer PBR calipers that I have on the shelf. Maybe new pads, rotors, and calipers will clear it up or give me the critical clue.