So, if you're following lately, I had a replacement engine fan explode after 2 weeks and tear up my engine compartment. (it was MTC 7844 / ERR-4960 Fan Blade (Jaguar/Land Rover models)
Anyway, I got the Doorman fan # 620-112 as a replacement as recommended by others here. There are some issues;
1: It's REALLY loud. Not just a little louder.
2: Now when I drive in the cold I NEVER get above 195 at the hottest in traffic, and on a couple long mountain descents my temp has dropped all the way down to 105 (I have a sender on the upper radiator hose)
3: I swear there's a power loss from the bigger fan.

That's too cold for me. I have the 180 thermostat also, but it never used to get that cold on the same roads.
I notice, even in the cold, even at high RPMS I never hear it shut down (the clutch never seems to slip and cycle down). I'm using the hayden 2991 clutch, it's brand new as of the exploding fan. So now I'm also wondering if maybe this clutch isn't slipping the way it should when cold, which potentially also made my other fan spin too fast. It has the usual peanut butter feeling inside when I spin it by hand.

Thoughts?
Do I need a replacement clutch? Do I need a lighter duty clutch?

 

Since you are in CO, I’d probably use the OEM temp thermostat if you want it to run warmer, or do like the truckers do during the winter and partially block off some of your grill to allow the engine to run warmer. The 620-112 fan blade isn’t any larger than the OEM unit. The fan clutch is new & usually they’ll break in after a while.

Quickest easiest thing = block some of the grill for more engine temps.

 

Just realized the 2991 clutch is the heavy duty version whereas the 2781 is the standard replacement. So I'm guessing I should just switch out to the standard 2781.

 

I have this same issue on my commute back from the sierras at night here in California. What I do is drop down to a lower gear while descending, helps keep speed in check to give breaks a rest and maintain a higher temp. I also got some mesh banner material and made a radiator screen like mentioned above. I'll drop down to 155 sometimes but maintains tamps nicely. I do this cause I'm to lazy to swap out thermostats like I should though!

 

@Broken08 the heavy duty fan basically "locks" sooner and for longer so you get better cooling but as you noted but it can be too cold. Here is a link to the Hayden spec page , you have a severe duty fan https://www.pageturnpro.com/Publicat...%204-20-10.pdf Great in the summer is my bet a little cool in the winter as you discovered.

 

How would a bigger fan drop your temps that low The 180 stat would just cut circulation to the rad

 

I'm wondering this as well.

Not to mention, gas mileage would suffer from the fan and the air flow.

 

Even when the thermostat is “shut” it still sends 10% of the coolant to the radiator, but yeah, the temps still seems too low. Perhaps if you are in cold climate (which CO is) it would do that.

At any rate it’s problematic because the ECU will think the engine hasn’t warmed up and run it in “open loop” in which it’s running full rich which is probably part of why your fuel economy and mileage aren’t great (not necessarily due to the fan clutch per se). Too long like that and you will torch your catalytic converters too.

 

Going down a long mountain pass in cold temps, with little to no throttle input, and at 45-55MPH could certainly lower your temps since the engine is just basically at idle and being over cooled. Block off some of the airflow to the radiator and BINGO problem solved.

 

This is why you see rigs on the highway in northern and western states with the radiators covered over in winter. It's simpler than switching out the fan system to math the season.
Even so, the heavy duty clutch might be overkill.