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     While everybody is familiar with  standard end covers for Sauer Danfoss series 90 closed loop hydraulic pumps, along with a widely used option of charge flow filtration, the special filter holding   manifold you can see on these pictures is not so widely spread, and, probably, that is why it often arises questions and doubts among mechanics. Instead of answering the same questions once a month, I decided to create this reference page with a brief description of this gizmo.

     This manifold, mounted on a special end cover, is prepared for charge flow cooling purposes, and carries charge pressure screw-on filter, thermal bypass valve, cooler connection lines, clogging indicator, and filter element bypass valve. Its main advantage is the thermal valve, which will bypass the radiator flow until a certain temperature is reached (schematics), allowing the circuit to reach optimum temperature fast. The thermal valve is a simple wax motor, like this one, which pushes the small rod out when the material inside the brass part expands.

     Whenever you come across such an option, make sure to check the function of the thermal valve - when you heat it the rod must come out. A faulty thermal valve can cause overheating, which is especially dangerous in case of compact circuits that use the pump's case as an oil tank (read the article about these pumps).

    Also, the clogging indicator poppet is driven by a magnet, and therefore when dirt accumulates inside the small hole it's lodged in, it gets stuck, so make sure to keep it clean.

    The manifold is also equipped with charge pressure measuring port, which is connected to the line that feeds the closed loop (after the filter).

    The pictures and the schematics are pretty much self explanatory.
Thermal bypass and filter manifold, Sauer Danfoss series 90
Thermal bypass and filter manifold, Sauer Danfoss series 90
Special end cover, Sauer Danfoss series 90
Thermal bypass valve, Sauer Danfoss series 90
Thermal bypass valve, Sauer Danfoss series 90
Clogging indicator, Sauer Danfoss series 90