[olddog]

As stated a line lock is intended to be activated for a very short period of time. Aside from the solenoid coil getting cooked and draining the battery, hydraulics bleed off over time. Additionally hydraulic fluid changes volume with temperature. It will also boil if too hot, the reason why large trucks have air brakes.

So in short, this is a very bad idea. Just fix the parking brake. That is what it is made for.