1939 Plymouth Brakes

[likaleica]

Hi guys - would be very grateful for some guidance please on sorting the brakes on my newly purchased 1939 P7/P8 hybrid export model sedan.

The brakes have been restored by a previous owner with all new brake lines, flexible hoses and judging from their appearance, new wheel cylinders. But when I bought the car the foot pedal went straight to the floor with no braking action.

We've bled the system in the normal way and a good deal of air came out. Now the brake pedal is solid - overly so because there is no movement at all once the free pedal movement is taken up. The manual says there should be an inch of movement AFTER the free play. We've got the rear wheels jacked off the ground and we can turn them when the foot pedal is pressed down. Any advice would be well received as we're scratching our heads here!

Thanks guys

[shovelheadrob]

It sounds like you might have a problem with the master cylinder, or the adjustment between the master cylinder & the pedal, you didn't mention it has been rebuilt. Is it a dual circuit? Can't remember when they started using them, I thought it was a lot later. I know that later cars have a brake block (usually just below the master cylinder) that if it fails could cause a similar problem.

[likaleica]

Cheers for that. Would be interested to know what the brake block is, what it's for, and how to tackle it.
I don't know if the master cylinder has been rebuilt, as I bought the car from a dealer who acquired it after the previous owner died. It came with no history. But I'm fairly familiar with car restoration it looks to me that the whole braking system was refurbished maybe 10 years ago when the entire car was lightly restored. I am fairly sure the system is single line.

[likaleica]

Cheers for that. Would be interested to know what the brake block is, what it's for, and how to tackle it.
I don't know if the master cylinder has been rebuilt, as I bought the car from a dealer who acquired it after the previous owner died. It came with no history. But I'm fairly familiar with car restoration it looks to me that the whole braking system was refurbished maybe 10 years ago when the entire car was lightly restored. I am fairly sure the system is single line.

[shovelheadrob]

If it only has one line from the master cylinder then it is not dual circuit & will not have the block which is actually a proportioning valve, all it will have will be a "T" piece or 2 & possibly a compensator/pressure reducer in the rear brake line. Sorry I can't be more specific, the oldest Mopar I've worked on was from the '50s. I think you will just have to go through it all systematically starting at the pedal.

[jagracer]

It will be single circuit, does it have a residual pressure valve, this could be stuck or if not it sounds like the problem will be the master cylinder.

[mr_spock]

I'm not sure about a '39 - my '57 has the first of the "total contact" drum brakes - but it sounds like one wheel may have the shoes on wrong, or the backplate upside down, so one front wheel shoe hits the drum and that's the end of the MC movement. You need to get one of the bleed nipples open and see if the MC moves (which would eliminate hydraulic problems in the MC). If it does, it's in a wheel.