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.