Front disc brakes locking up question.

1971 Plymouth 'Cuda 440-6 power brakes with stock front disc, rear drum.

Both of my front brakes seem to be locking up. The car drives and stops fine.   I can't feel the brakes drag and the car does not pull to one side or the other when I apply the brakes or when cruising. I noticed a lot of brake dust on the front wheels so I jacked the front end of my car up and both front wheels where really hard to spin by hand, like really hard.   Both rear wheels are fine. The parts that are new or freshly overhauled: power booster, master cylinder, both calipers, discs and pads. At that point, I replaced the master cylinder with a different overhauled one.   Same problem. If I let the car set for a while, the pressure lets off until I drive the car again. Any ideas?


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take off the line from the M/C port next to the firewall and stick a drill bit deep down into the brass cone seat & you'll feel the springy RPV if it has one. Thread a screw into the cone and lever it out then toss the RPV then replace the brass cone seat. If it has no RPV check that the calipers ain't hanging up on the grooves (sliders) & if good there replace the calipers. Some calipers dont retract the piston enough for minimal drag. EDIT I'm assuming the line next to the firewall goes to the front discs

I suppose that you mean Residual Pressure Valve by the RPV reference?

Id crack the front line open to see if there is pressure. If so check to see if the front wheels are hard to turn still.

or crack 1 caliper at a time. if they are holding pressure its possible that the rubber lines are bad.

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I suppose that you mean Residual Pressure Valve by the RPV reference?

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Yes