This was a curious question I had on these viscous engine fan drives that are very stiff and run even when the diesel engine is cold. The Horton fan clutch design is beautiful because it does not move an inch until the engine temperature reaches the proper reading. I went on Youtube and found this video on how to adjust a viscous fan drive. There it was … a reasonably good video that showed the 2 tiny torx screws that have to be loosened off to adjust the bi-metal spring that locks up the fan when engine heat is at a preset temperature.
Unfortunately the MaxxForce 7 diesel engines in our fleet all run cold longer than the other buses with a Horton style fan drive. Later when I got in to the bus purchasing we learned that an electric actuated fan drive was available as a $300.00 option. Oh my God are you kidding me? All that driver grief trying to warm up the interior of their bus in the winter by going up a hill and back before the beginning of their trip to warm up the engine that’s running at 140 degrees.
I scratch my head some days wondering why certain designs were chosen for buses that pick up special needs students and just drive around the suburbs. The chances of warming up a bus in this scenario is slim to none. Kids in wheel chairs sitting in a cold bus is not a favorable position to be in. I adjusted a couple of viscous engine fans on the MaxxForce 7 engines and it actually solved the problem of overheating. On the road test the fan kicked in sooner and helped cool down the engine.
This coming Winter most likely the viscous fan drives will need to be reset back to come on later so the engine temperature will rise sooner. It’s a world of experiments with these engines that pump black smoke out of the exhaust like the train called ‘City Of New Orleans’. (Lyrics from a Woody Guthrie song) We’re stuck with this dilemma. Poor engineering has cost a lot of money to MaxxForce owners and it will not stop until someone offers a few bucks and takes these white elephants off our hands.
Most of our 18 MaxxForce diesel school buses are limping away or being used as spare buses to keep the mileage down. At least adjusting the viscous fan drive does not cost anything reminding me of decades ago where you could fix things and spend much less on parts. Down the road the scrap metal business owners will be thanking us for our contributions.