I am not sure why this didn't work the first time. If I am repeating myself than please ignore this. I am thinking about putting a heater in a oil cooled skidsteer myself and wonder if it is much different than in a liquid cooled machine. Any pointers are appreciated.
Is this a Deutz engine by any chance, and what type of machine are you installing it in? I only know a little about Deutz engines and heaters.
You are correct, it is a Deutz and it would be in a Gehl machine. 6640.
On a Deutz, there are ports specifically designed for the hoses that run to your core. They have springs and poppets inside for checking back-flow and pressure regulation. You can't get away with non-oil-resistant heater hose. I believe heater core construction is different also, as there is different pressure and fluid viscosity to worry about. Your control valve will be different, built to handle oil instead of a water mixture. Other than that, the concept of operation is the same.