2008 Marquis Fan Control

[Bill Donley]

Trying to make a hydraulic system diagram for my 2008 beaver marquie C15 Rv.  The hydraulic oil cooler was repaired twice.  Trying to understand the problem. Per my manual the hydraulic diagram is incorrect. The power steering has its own pump . It shares the same fluid reservoir and oil filter. It has its own pump connected to a PTO from the engine.
The fan motor is driven off a gear pomp powered off a PTO from the Allison transmission. 
I’m not clear on the location of the wax valve which controls the radiator fan motor.
I’ve learned that my hydraulic pump for for the radiator motor has no valves. It’s a gear pump only. 
I assume that my problem is with the system that controls the fan motor.
I also learned that this aluminum oil cooler design that has a pressure relief valve cross over pipe that causes thermo stress which results in aluminum weld cracking.  My coach has 70k miles and now I have this issue.
Not enjoying this hassle.
I ordered a new hydraulic oil cooler and will be using a lighter weight oil.
Any thing you can tell me about what you went through and learned I’m listening.
Bill Thousand Oaks CA. 818-421-3575

[Frank Bergamo]

Bill,

there is a switch valve mounted to the fan motor that hooks to to thermo/wax valve. The thermo/wax valve controls the fan speed as the coolant heats up. I believe it restricts the fluid, forcing it through the fan motor, spinning fan faster, to increase cooling. Don’t really know the function of switch valve, other than a bypass to return fluid back to system reservoir. The thermo/wax valve is mounted in the radiator, look for two smaller hydraulic lines running to thermo/wax valve. Hope this helps.

[Bill Donley]

Bought a new oil cooler.  Was told the the cross over bar caused uneven expansion.  Put in a lighter viscosity oil. Coach is running but I haven’t gone on a trip.  Hopefully the new oil cooler is correct fix.