R70 Heating

Have a R70 with Duetz. The history is, started heating. I replaced the fan, that helped, then oil would heat real bad. Replaced the thermostat. That stopped that.Now, cylinders get hot. It is clean, have taken air cleaners off and complete top and cleaned very good. Air conditioner doesn't cool very good The evaporated is very clean. It appears there is not enough air movement. My question How do know the cause? What about the drive? I suppose there is pump and a motor

R70 Heating