drivers side read brake locks up

[jsgomes1950]

I have a 1940 LaSalle. 5019 four door sedan. The drivers side rear brake started locking up out of the blue. I decided to do a complete brake job on all four corners which I did. I rebuilt the rear wheel cylinders and replaced the fronts. When I got the drivers side wheel cylinder apart I found it completely gunked up. Passenger side not much better. I honed them both and replaced all internals with new parts. I finally got it back together today. I went to take her out for a test drive and before I could get it out of the driveway it did the same thing. I put it into gear, step on the gas, and the second I take my foot off of the gas it locks up! What the heck could be causing this? The only thing I haven't tried is to disconnect the emergency brake cable as a test. Anyone have any suggestions?

[Abe Lugo]

This could be a stretch but sometimes the rubber hoses are the issue. It could be you need to flush the hose, at least know that clean fluid is passing through.
In your case you pull the wheel and see if that side is still leaking. Or check the backing plate.

If you do pull the wheel and drum, I would double check that the cylinder pistons move smoothly through the cylinder.  I would also ask why didnt just start with clean up/replacement of the messed up cylinder? If you do them all, then you added too many variables to the the part at fault.

If it was gunked up the cylinder and was leaking,  the shoes  MAY got brake fluid on them, that can also be an issue. If the shoes look glazed or oil it may be why they are grabbing funny.

Also check the basic adjustment of the shoes.

I recently was getting a grab on one side another vintage car, the cylinder was plugged up and I had to hone and flush out all the fluid in that line.

[35-709]

Brake hoses can and do fail (collapse) internally, it has happened to me more than once.  That is why the best thing to do when going through an unknown brake system (or a known older system) is to replace all of the rubber hoses.  Enough pressure can be exerted by the master cylinder to force fluid past the bad spot in the hose but the fluid cannot return and maintains pressure on the wheel cylinder.

[TJ Hopland]

Is it possible that that is the only brake that is working properly? 

[Dan LeBlanc]

Geoff's answer is right on the money.

I had the same problem with a 79 GMC Van once.  I replaced calipers, pads, rotors, rear shoes, and cylinders, bled the system, and the brakes wouldn't release.  Crack a bleeder screw and the pressure would blow the fluid out and the brakes released.  Light applications and it would take a bit for the brakes to fully release.

Someone told me the same thing.  Collapsed hoses (or at least swollen internally).  Replaced all the flex hoses, problem solved.  Cut one of the hoses open and it was so swollen inside, that I couldn't even pass a needle through it.

[Jay Friedman]

I would add to what everyone said about hoses that a bad hose can look perfectly OK from the outside.

[Bob Schuman]

Another possibility is reversing the primary and secondary brake shoes. The shoes are identical, but the linings are not. The shorter lining goes toward the front, the longer toward the rear, and having them reversed can cause very easy lockup.

[jsgomes1950]

Thanks for all of the input guys. I did in fact replace the hoses. When I bled the brakes I made sure I got clean fluid at all four corners. Pretty sure I got the shoes on correctly. I took pictures with my phone to look at when I put them back together. Rear shoes can only go on one way because of the parking brake cable. Is it possible that there is something wrong with the rearend? It only happens when I lift my foot off of the accelerator. Doesn't happen in reverse, only forward. It will lock up two of three times in a row, then not do it for two or three times.