Rear brake cylinder problem.

[HROP]

Hi,
the car is a 2000 Accent GL.

Recently I changed my tires,
and I have noticed that the rear wheel drum cylinder was depressed all the way out even though no pressure was applied on the brakes.

I proceeded by replacing it with a new one.
But still the same problem occurs.

Anyone has an idea on what might be going on.
I've read some stuff on the proportioning valve, but I have read there is none on this model.

What might be going on ?
I don't mind changing the master cylinder, if this is the cause of the problem.

Thanks for your help !

See image for reference.

[J.P.]

Does this happen only when you remove the drum?

Is the drum locked solid or dragging heavily before you remove it?

Is it only happening on the one drum?

[HROP]

Hi,

I believe this happens on both drums. Didn't check the other drum yet.
I have planned to replace both drum cylinders, but I didn't disassemble the other side, because I am not sure of what is going on here.

I believe the drum brakes were dragging before, I remember hearing heavy rattle for the first few minutes, when the car was parked overnight.

The piston on the left side of the old cylinder was pretty much stuck in place, even without oil pressure it didn't want to move (I emptied the entire hydraulic line).

It's hard to tell what would happen if I put the drum back, but I doubt the problem would fix by itself.

[J.P.]

The return springs should be strong enough to pull the shoes home. If the adjuster is turned out, it will stop the shoes from pulling the wheel cylinder back. If the parking brake cable is seized, it will hold the shoes apart. if the parking brake lever arm is seized to the shoe (common), it will stop the springs from pulling the shoes back.

Things to check:
Parking brake cable cable not seized.
Parking brake lever on trailing brake shoe not seized at pivot.
Self-adjuster rod backed off (and positioned correctly in both shoes).

If all of the above look ok, manually pull the shoes back to fully retract the wheel cylinder. Then set the shoe to drum clearance. Make sure all the shoes contact points to the backing plate are lubed so they return easily.

The only other thing I have seen which could cause that is a collapsed flex line. It can act like a one way/check valve - fluid goes in, but when you release the pedal, is does not flow back. If you cannot retract the wheel cylinders without opening the bleeder, this could be the case.