Sundstrand Sauer Danfoss Series 20 Cooling Circuit

When excess cooling oil that comes from the manifold charge pressure relief valve after it goes into the motor case, and it flows thru the case drain lines to the pump case. The cooling oil is transferred thru each of the hydraulic elements in the series to help in cooling. It then exits the pump case, goes thru the heat exchanger and is put back in the reservoir.
The by pass valve is to help eliminate high case back pressure at the heat exchange when it is cold oil or in a restricted cooler.
Even periods of operations when the main pump is in neutral, the shuttle valve is closed and the extra fluid from the charge pump is guided to the cooling circuit by the neutral charge relief valve in the charge pump. The cooling flow is not administered to the motor because it is at rest, when you run it this way.

If you need further help with this top, please let us know.
800-361-0068
sales@hydrostatic-transmission.com