The overheating problem with the rock crusher machine was interesting in that it overheated when idling or coasting but if loaded for hours, the cooler handled the heat exchange.
However, when idling or coasting, the large pressure compensated pump was fully compensated at 3000 psi, and the hot case drain oil was not cooled. The case drain was plumbed directly to the tank while the cooler didn’t see any system oil flow to cool.
We have found that providing the pump case drain with a set of check valves — one with a 5 psi setting plumbed to the tank and the other a ½ to 1 psi plumbed to the main cooler — would have reduced idle heat buildup in the system. When the system is working, fluid flows from the actuators, and while idling, the only heat source from the pump case drain is cooled. This solved their problem.
If the operating system does not require a heat exchanger, but idles for long periods of time, a small air cooled heat exchanger can be installed on the case drain of pump.