Loss of Power after New Fan Clutch

jonaz wrote:
Thank you everyone for your replies. There definitely is a problem with the new fan clutch. At this point, I am going to replace it with OEM.

If you replaced with an aftermarket parts store unit, the chance is great that it’s defective.
If I have to go to a Vato Zone or O Really?s, or even Nappy anymore, for an actual mechanical/electrical part, I accept or expect about. 50/50 chance that the part will either A perform as intended out of the box, or B will have a reasonable or expected lifespan.
Was not the case years ago, and having worked as a mechanic professionally as a teenager (30 years ago, some parts stores were quality and some were cheap like the strip mall chain stores) and performed 99% of the work on all our vehicles since then, I’ve seen a sharp decline in quality in the last 10 years or so.

@benk, many newer fan clutches are electric operated including the OPs truck. Not like your old iron. Newer ones are able to and come on in stages as needed.

jonaz wrote:
Thank you everyone for your replies. There definitely is a problem with the new fan clutch. At this point, I am going to replace it with OEM.

Good call.

Thank you everyone for your replies. There definitely is a problem with the new fan clutch. At this point, I am going to replace it with OEM.

Another potential that is forgotten about the current OATs & HOATs coolants

They all have a nasty reaction, or activation, during a very high temp event.

Since the 'A'cid component works by etching metal down to clean metal & plating a protective layer of organic...it leaves the etched off oxide(s) floating in the coolant till it is flushed at the manual's recommended frequency (miles and/or time based).

During a very high temp event, that floating glob of acid/oxide reacts in that high temp area. Most typically inside the radiator tubes by sticking to it. While there, it attracts more of these floating globules. Creating a narrowing of that tube, which reduces the coolant flow, which exacerbates the thermal rejection rate, which then creates an ever hotter spot.

Also eats away the radiator tube from the inside. This also happens in other coolant radiator tubes...like the heater core.

Meaning the OP's radiator might be compromised and needs either rebuilding the radiator by rodding it out & new tank gaskets...and/or...a complete coolant flush.

The radiator fan on my Fiat Qui-Qui comes on after pulling away from a stop and and stays on until 25 mph. Doesn't matter if it's 100 degrees or 20 degrees. Dealers have said it's normal. Since I'm not familiar with the Qui-Qui's, I have learned to ignore it.

Fan clutches are not digital...meaning that they are only on or off with no middle coupling

They are analog...meaning that they will start to couple more over their parasitic as their thermo sensor says it is getting hotter...until it says to turn FULL ON. At which point it ROARS

You can get by with a much smaller mechanically coupled or electric by increasing the radiator's thermal rejection capacity (larger frontal area, but stuck with the vehicle sheetmetal opening...or increasing the stack...and/or increasing the tube/fin efficiency)

It is a whole system...thermal management of the ICE coolant ICE oil, and auto ATF. Toss in the AC radiator.

Heck, even the flow rate (both PSI & GPH) of the coolant running through the radiator matters...as it is a component of how the thermal system works.

When towing heavy, my Suburban's SD fan clutch rarely ROARs, but when it does...a quick look at the dash thermal gauge shows it is crept up to 200*F. That then has the gauge needle drop like a rock back to 180*F (my thermostat rating). Maybe a few seconds if on the flats, but on inclines it might ROAR for a few minutes and will cycle if that incline is long.

It appears the OP was just venting, and or looking for some magic beans with which to fix his truck. 1 n done on this thread probably.

I'm presuming one of the components failed, took out the belt which took out the other (probably water pump murdered the fan with a thrown belt). Regardless, without more info, who knows....
Heck, maybe the new t-stat aint opening all the way, causing the engine to run hotter and thus the fan to be working overtime.
I don't think an old Hemi has any de-fueling due to temperature built in. 06 6.1 Hemi Charger we had, went about 2 years with increasingly failing electric fans. To the point only one of them would work at low speed and the other didn't respond. That car would still chit and get even though under the right conditions it would run around 230 degree coolant temp, until I replaced the fan assembly.

I've heard the fan kick in on my F350 and have other other trucks I've owned. But, it doesn't happen often and the loss of power has always been minimal. The race cars/trucks/etc all have electric fans, and much larger radiators and more oil cooling.

The last time it happened on the F350 was during the big heat wave and fires in Colorado (June 2018) and I was pulling our 5th wheel up and over Monarch Pass. We got to the summit a little after 5 pm so it was the hottest part of the day.
2005 V10 with 4:30s, all new fluids, new belts, hoses, etc., plus a clean condenser and radiator.
The fan only came on once for about 20 seconds 1/2 way up.

The entire trip was hot. But the fan only kicked in once.

Here's the elevation profile




FWIW, all the other trucks shown in the foreground of the photo were mutual aid Firefighters heading home to Oregon, after spending 3 weeks in Colorado. Every crew truck had a gas engine.

In 13 years I have heard that roar 2x, both times about 30 secs on my Duramax.
Yea, I know, different truck, different etc, etc,.
If it happened very often I would have junked the truck. That is a terrible noise!!
Along with reduced power, you know something is wrong.
Take it back to where it was repaired and don't take no for an answer. You know people would not be buying trucks if that is normal.