I assume you're operating the loader with the remote valves, since the problem affects both loader and lift system. The main section of the hyd pump supplies both. The other pump section supplies power steering, which I assume still operates OK while this is happenning? If it does, it pretty much rules out a suction or supply problem as the pump sections have a common suction inlet. If one starves, they both will. It wouldn't hurt to check all the suction hose connections and give the hose clamps a twist or two, but it doesn't sound like that is an issue. I suspect the problem is in the remote stack. It's a power beyond type system, oil flow goes through the valve stack first, then to the lift. If the lift were the problem, the remotes would still work since they are first in line. The valves themselves are not prone to cause this type of problem without there being something unusual about how one or the other acts or feels when it is used. The relief valve is the most likely thing to check first. There are 2 o rings and backup washers that have been known to fail and cause enough internal leakage to be a problem. It may work for a few minutes until the oil warms and thins enough to start leaking by. The relief is threaded into the inlet section of the remote stack and can be removed as a unit for repair. You can get a kit for it which comes with the o rings backups a new spring and I think a new pintle. It's a Husco valve and parts are available.
