TeGGer® wrote:
> There is the possibility that the cable is rusted internally. Is the rubber
> bellows still intact or is it split?

The cable and boot are fine. It moves perfectly smoothly. It ratchets
the arm from a retracted position exactly similar to the right side,
when the p-brake handle is fully released, all the way to the stop pin
that looks like a little mushroom.

This clearly indicates that there is a problem between the point at
which the arm is attached to the cam shaft and the piston. If I read the
diagram right it could possibly be simply that the parking nut and lever
are loose, so I'll definitely check those. Thanks for the push.