hydraulic fan on a 8v71

[la chiva]

hey guys

i need advice my 4107 with the 8v71 as a direct drive fan to cool of the engine it runs all the time very hard to get the temperature up
and use lots of hp. ibought a 4905 for parts this one seems to have
a hydraulic fan that turns free when the engine is cold but have no idee how it works can anyone help me understand this how it works

thanks

[zubzub]

Are you sure yours is direct drive, even the later 4104 had a  fan that was controlled using engine oil pressure and a thermostat.  Sometimes when the thermo failed people would lock it "on" though, can't remember how.  Maybe yours has been locked on, check the manual.
BTW a true Hydraulic fan would be one using a pump (like a big PS pump) and a hydraulic motor.  The later 6V92 ect in Transits have this.  Pretty cool set up, lets you really squeeze a fan/rad/ motor anywhere you want.

[la chiva]

the 4107 i am sure when the engine is not running you can not turn the fan by hand the air conditionning was remove on the bus and they put a plate where the drive shaft use to be connected. the 4905 where the fan is connected it's a round housing look like there could be a impeller
inside from there a hdraulic hose that connect to a T on the radiator hose looks like some kind of valve and on the other side of the T the hyd.hose goes back to the engine oilpan

[buswarrior]

look up "torus fan drive"

Engine oil pressure is used to regulate the cooling fan operation depending on engine coolant temperature.

happy coaching!
buswarrior

[Just Dallas]

If you can't turn it when the engine is stopped, I would agree that someone locked the torus.
Do you have the service and maintenance manual for the coach? That is where you need to start.

[la chiva]

thanks guys
i didn't know anything about these torus fan but by looking at it
i was pretty sure thats how it worked so i will take this fan from the 4905 and put it un my 4107 because that one is completely direct
the hosing of the fan is different thanks again for the info these bus and engine are still a mystery for me but learning and enjoying every minute of it