The excessive heat and contamination problem — which only appears in the dump cylinder — is caused by the oil going across the meter oil flow controls that generate heat. The long lines going back to the power unit don’t allow this heated oil to return to the reservoir and is then pushed back into the cylinder only to exit over the flow control again. If the flow controls would be re-located at the power unit, the heated oil could return to the reservoir. This would greatly help the oil over-heating problem. However, the same oil would be recycling in and out of the cylinder.

This condition could be fixed by adding a small, 1/8-gpm fixed pressure control flow control with  an outlet check in series mounted close to the cylinders plumbed from the cap to the rod outlets. This would allow a small amount of oil to migrate every cycle from one side to the other always adding fresh oil to one port and returning dirty oil back to tank.