The factory cooling system worked fine with my stock truck, but with my heavy load and BD performance enhancements, keeping the engine cool required modifications. In anticipation of modifying my engine to improve performance, I added the Horton fan clutch in early 1999. With the stock engine the fan only came on during long upgrades and when driving slowly in hot weather. With no engine performance modifications the fan only ran about 5% of the time. Now that I've added engine performance enhancements, the fan comes on much more frequently.
Horton Fan Clutch
The Horton fan clutch is one of the best upgrades I've made to my truck. The Horton clutch is an electro mechanical clutch that engages when the engine water temp hits 200 degrees Fahrenheit. With the stock viscous coupled fan, the fan runs with at least partial engagement all the time. This provides unnecessary cooling when the engine is cool, causing longer warm-ups and robbing engine power. When the engine is hot, the fan is still not 100% engaged, since it never fully locks up. The Horton has the benefits of faster warm-ups, less engine drag resulting in better performance and mileage, quicker cool downs and improved reliability. I estimate a 1 to 1 1/2 mile per gallon gain with the Horton, and it only engages in stop and go driving and on long slow grades. The only negative is cost, and poor customer service. The installation instructions were incorrect for my engine causing several months of grief. The instructions showed an incorrect location for the temperature switch, and the fan was not engaging when the engine got hot, even though the manual switch worked fine. Horton's customer service was no help resolving the problem, but I finally relocated the temperature switch and solved the problem.
I had a serious problem with my Horton fan clutch that I attribute to a poor bracket design. The Horton installation kit uses a metal bracket to keep the fan clutch wire from being sucked into the fan. Unfortunately, it is easy to accidentally bend this bracket when working on the truck. This happened to me when I was having work performed on my truck, and the fan clutch was destroyed when the fan engaged and hit the metal bracket. When a replacement fan was installed, we did not use the supplied metal bracket but used wire ties instead.
I have a toggle switch on my gauge panel to manually engage the fan. I also have a momentary contact switch and relay that will engage the fan and automatically reset when the engine is shut off. I use this when the engine is heated up and I know I'm about to stop. A mile or two before I get to my stopping point, I hit the cool down switch. The fan stays engaged until I shut off the engine. When I restart the engine, the fan is no longer engaged.
The factory engine temperature gauge is really just a idiot light. It will tell if the coolant is cold or hot, but it really doesn't tell how cold or hot the coolant is. I added an Auto Meter engine coolant gauge and it is much more accurate than the factory gauge.
Keeping debris out of the radiator is critical to keep the cooling system functioning. A radiator clogged with bugs, or damaged from a tree branch or rock can easily cause overheating. My Deflecta-Shield bug screen snaps over the radiator to keep out small debris and my Stull billet grill keeps larger objects from damaging the radiator.