Hydraulic Cooling Fan Drive (LS & Thunderbird Only)
Hydraulic cooling fan drive system consists of an engine driven hydraulic cooling fan pump with integral solenoid (activated by PCM), oil reservoir, hydraulic lines and hydraulic cooling fan motor. See Fig 1. Hydraulic cooling fan motor shaft drives the cooling fan by hydraulic pressure supplied from cooling fan pump through high pressure lines. Varying voltage from PCM to hydraulic pump solenoid, opens or closes pump solenoid to change amount of fluid flow and hydraulic pressure to hydraulic cooling fan motor. When PCM increases voltage to pump solenoid (opening solenoid), it increases hydraulic cooling fan speed by increasing fluid flow and hydraulic pressure to hydraulic cooling fan motor. Hydraulic cooling fan motor is able to turn at all times due to pump solenoid current leakage, even when engine is cold.
