Joe, help me understand the Gen1 hydraulic fan behavior please

[grizzlyls]

SO after recently getting rid of the defective oem tstat for a stant, it all behaves much better and runs significantly cooler. This last weekend was a superhot though at 105 outside. Took about a 30 minute highway run to friends and monitored the coolant temp to be safe. At 70 mph it crept up to just over 220 and I didnt hear the fan so much. Pulling off highway, with lower rpm and city street fan comes on right away and I can hear it easily.Temps also drop down quickly to about 208/210.

Thinking on it, I do believe that I dont hear the fan as often running at high rpm on highway. Is this normal? The load definitely heats the engine up, and I would prefer the fan came on and kept it at 210 ish. I am thinking that may be the normal Control behavior, just like when I am on city street, the temp may be near 200, but if I give it gas off a light the fan will ramp up for a few seconds. It seems to be trying to balance fan to load, more than temp.

Share some insight?

 

[joegr]

My experiences with this are with the electric fan. That said, I am pretty sure that the control strategy is the same either way. My understanding is that the fan is turned off (lowest speed in the case of the hydraulic fan) above a particular vehicle speed as long as the engine is not overheating and the AC pressure is not too high.
I think that this is done to increase gas mileage, as the fan should not be needed when there is enough airflow caused by the movement of the vehicle.

 

[RigsLS]

Grizzly, you may also want to check for obstructions in front and between the many so call rads down in front.

When I first took possession of my '01 V8 Sport back in 2012, I found much hardened up, caked on dirt surrounding a piece of plastic bag. I had to run a garden hose in between the radiator and the oil cooler to get it free'd up. Used a thin wooden stick to push it all out. Rinsed and cleaned up all the rad fins and such. Didn't have overheating issues but sure didn't appreciate all that crap that had gotten in between.

Plastic lower shroud has to be in good condition as well. Airflow circulating within is paramount.

~ something to think about.