No rear brakes 1966

[eastmedia]

Hello All,
Hoping some of you might be able to help with this issue. 1966 Single master brake cylinder.

Had an accident a few months ago which involved locking up the brakes and taking a hard impact at 25mph.
Immediately after the rear brakes were locked up. Had to back off the adjusters at the body shop just to move the car.

Now that its home, it seems there is no rear brake function. If I step on the pedal the front brakes work, although they seem slow to recede into the bores.
The rears though do not function at all. The cylinders dont expand. There is no leakage, so I dont think they came out of the bores, visually they look fine. I tried to squeeze them back into the bores, but the dont move. It almost seems like maybe the rear brakes never worked? Not much brake dust or wear on the shoes. But the locking up after accident has me stumped.

Is it possible the proportioning valve is bad, restricting flow to the rear cylinders?

Is the MC bad not allowing flow to the rears?
Thanks for any ideas.

[JT68]

In the 66 system, there is no proportioning valve. There is a pressure bleed valve in the master, but that's not your issue otherwise the fronts would be locked as well.

Yes, if those rear cylinders are ancient, both could have been siezed and when you slammed on the brakes, you forced them into an extended position where they are still locked.

Usually only one side freezes up ar a time, but if they are really bad, possibly both since there isnt much else that would cause this.

If both were siezed it sure will stop better with new cylinders! Give us a shout if you need them.

[C.Costine]

Brake fluid sucks moisture out of the air, and since water is heavier than air the water slowly migrates to the low point, the wheel cylinders. If a vehicle is driven regularly enough heat is generated by braking to vaporize the moisture in the system. Otherwise the water sits in the wheel cylinders corroding the walls. It is probably a safe bet that your '66 has experienced an extended sitting period or two since the rear wheel cylinders were last replaced, so it is very likely that they are seized. They are available new for short money. While in there I suggest that you also replace the flex hose to the rear axle if you haven't yet. Silicone brake fluid does not absorb moisture, and as an added bonus it doesn't hurt your paint!! If you make the switch you need to carry out extensive bleeding to eliminate all of the old fluid.

[eastmedia]

Thanks. Exactly right. Seized. Happen to have 2 sets of 510 cylinders plus new steel lines waiting for another project. Done.