66RBS

I recently had my 66 power brake master cylinder professionally rebuilt. When I bench bled it, the kit only contained one fitting so I bench bled it one chamber at a time. Road tested and seems fine

When I advised my mechanic what I had done he said I likely have air in the master cylinder as you have to bleed both chambers simultaneously.

When I road tested I can lock up the wheels in the back only; not front.

Car has J 56 proportioning valve so issue could be there or air in the front circuit.

Do I need to take the master cylinder off again and bench bleed again?

Randy

66BlkBB

Not sure I can help but I'll try. I have the same setup, including the J-56 option. I bought brake lines, cut them to length and bent them so they returned the fluid back to the reservoir when I bench bled the master cylinder. Not sure it worked though. I went a different route on the vehicle. I purchased a Motive bleeder and an adapter specifically for the 60's type of brake cap. I then bled the front system and then the rear system. Every thing is working great and has been for the last 6 or 7 years. I am enclosing a photo of the Motive bleeder and the adapter in case you want to go that route.

This is a combination unit for your brake system.




0102 Classic American and Marine Trailer Bleeder

Motive Products

$ 74.95

Features custom cap to fit most early model American made cars and trucks with internally threaded master cylinder reservoirs from the 1930s through the early 1960s. Includes deluxe machined aluminum cap and brass swivel fitting. All bleeders come with a full 1 year warranty. The cap on the 0102 also fits many trailers with a hydraulic master cylinder. If the master cylinder has a male threaded cap 1.25" in diameter at the threads and 18 TPI you can use this cap to bleed the brake system on your trailer. This kit includes adapter 1102.

DUB

Not knowing how you bench bled the master cylinder with only one hose. Assuming that this is a dual reservoir master cylinder.

I would say you need to bleed out the system and make it so the master cylinder is as level as possible when doing so.

Pressure bleeding is what I do..but what ever approved method you choose will work.

DUB

vark_wso

The Motive pressure bleeder with standard '0105' adapter/fitting will cover both cavities of '66 p/b master cyl. However, it really needs to be clamped down tightly; those little chain-hook things won't hack it.

Bench bleeding both is pretty straight-forward with a few fabricated items as shown in the photo below. Perhaps a J56 valve failure of sorts would make your road test braking as you describe?

66RBS

Yes dual chamber 66. I used the single fitting and hose for the rear chamber, plug on front chamber. Then switched plug and fitting and did front chamber. I should have run to the auto parts store again and bought a bench bleed kit with 2 fittings. Yes master cylinder was level on bench.

66RBS

I made a pressure bleeder out of a garden sprayer for my old single chamber manual brake 66 car. I'll dig it out and see if I can make a new adapter for the dual chamber


Re J56 it is only plumbed into the rear brake and I can lock up the rear brakes now. Maybe I need to experiment with the bias and see if I can lock up the fronts first.

Powershift

Years ago my 1969 AMX had the proportioning valve go out to the rear drum brakes.........front brakes were 4 piston discs.

When brakes were applied with any noticeable force, the rear brakes would lock up and send the rear of the car spinning out.........almost swapped front to rear a few times.

Replaced proportioning valve and all was well.

If yours is adjustable, and you feel it is in good condition, you can play with the settings.

Larry