Gotta Be Nuts
In my quest to completely understand the cooling system on our 1120 I am pondering the visco fan. Why? Well a strange thing happened yesterday while essentially idling down a 10 mile gentle sloped corrugated dirt road. 3rd gear left the revs pretty low but with enough braking to slow the truck. Well we are now in Arizona and the temp was in the 80's f. For the first time the engine temp rose higher (not super high, just above normal as I watch the temp now like a hawk due to our radiator issue) than I have ever seen and the visco fan did not engage. So, we stopped and pondered things a bit. Then we decided to not head out on any remote roads and drive the 20 miles downhill on pavement to a formed campground (and internet). So heading downhill since the engine was running a bit hot I put the truck in neutral and turned on the cab heater thinking that would help (remember this is my first vehicle without an electric temp controlled fan). Well of course the revs were low and old visco would not engage. Then I sort of had an idea, put the truck back in gear to get the revs up and turned the cab heater off. Low and behold the visco fan engaged and engine temp went right back to normal. So I turned around and drove back up the hill and all was ok. So I know the visco fan has some oil in it for it to function and is separate from the actual engine coolant temp. So, long story short, should the visco fan engage even when the truck is sitting at idle? Or is this just how they work? If it should engage at idle could the oil be low? Would there be any adjustment?