bcja
Junior Member
I have read all I can find on fan clutches, and I am still a little stuck. Been doing a lot of deferred maintenance over the last year (TLDR is/was my elderly father's, but now I drive it). I noticed a precipitous drop in fuel mileage after changing out the water pump and fan clutch (severe Duty GMB), but a few other things happened around the same time that might have had an effect.
Truck is a 2011 Ram 1500 with the 5.7 l Hemi, crew cab Outdoorsman 4x4. Stock as far as I know. About 146,000 mi. Viscous fan clutch, no electric fans (edit - the AC fan is there, I just hadn’t seen it). Before doing most of this work I had been towing trailers between Baltimore and Lower Alabama to move my dad and renovate his house. No real issues during that time.
This winter, before the big snow and ice storm and the weeks of freezing temps, I finally replaced the warped headers. That went well enough, though I broke a brittle evap line and had to make a new one using the old fittings.
While doing that I noticed the water pump was leaking. I ordered the GMB kit (with severe duty clutch) from RockAuto, on the recommendation that you might as well replace the fan clutch as well. I knew nothing about clutches at that time, this is my first truck. Good thing, as I could not get the old clutch off of the water pump. Had to get a new (Dorman) fan because I dropped the old one trying to get the new clutch threaded on and it was brittle, and the cowling also cracked during removal but I re-used that.
Even though temps were hovering around freezing, the clutch roared and would not disengage even after the engine warmed up. I ordered a replacement kit to return that fan, and also a new cowling. The new clutch was a little less noisy (maybe partly the cowling?) but still have the same noise problem and the fan not really disengaged even at lower temps.
Most of my driving now is in the city, and I feel like the mpg (measured by the truck) has dropped from around 11-12 to 8-9. It does do a bit better with extended highway driving. I've been logging data (there are no DTCs), and the LTFT is mostly in the 6-8 range which seems a little high, though in spec. O2 sensors seem ok voltage-wise (first sensors rapidly oscillating between 0 and 0.9 V). There is a difference between banks 1 and 2 (1 LTFT is 1.6% higher at idle, 7.8 vs 6.2%). I did not see any exhaust leaks with the home-made smoke machine, but not sure how much I trust it since I was pumping into the tailpipe. Plugs and boots were new last summer. I haven't messed with the fuel injectors, and I ordered an intake gasket kit and new MAP sensor for cheap and easy insurance (neglected to get one when I did the plugs). AC is not currently working. While smoke testing the exhaust I found a nearly broken ground strap which I sistered across the damage with some new ground strap I had. At this point I only expect marginal, if any gains in fuel economy from going down this route, but maybe I will be surprised.
Since I am not doing a lot of hauling or 4-wheeling, I am tempted to put a regular duty, or maybe just heavy duty, fan clutch in to try to improve mileage. Neither is spec'ed for this vehicle, so I'm hesitant. The other choice is to try another manufacturer's severe duty, like a Hayden, but from the posts I've read I'm not sure that a different severe duty clutch would be any different. Any opinions or suggestions would be welcome.
TIA
Truck is a 2011 Ram 1500 with the 5.7 l Hemi, crew cab Outdoorsman 4x4. Stock as far as I know. About 146,000 mi. Viscous fan clutch, no electric fans (edit - the AC fan is there, I just hadn’t seen it). Before doing most of this work I had been towing trailers between Baltimore and Lower Alabama to move my dad and renovate his house. No real issues during that time.
This winter, before the big snow and ice storm and the weeks of freezing temps, I finally replaced the warped headers. That went well enough, though I broke a brittle evap line and had to make a new one using the old fittings.
While doing that I noticed the water pump was leaking. I ordered the GMB kit (with severe duty clutch) from RockAuto, on the recommendation that you might as well replace the fan clutch as well. I knew nothing about clutches at that time, this is my first truck. Good thing, as I could not get the old clutch off of the water pump. Had to get a new (Dorman) fan because I dropped the old one trying to get the new clutch threaded on and it was brittle, and the cowling also cracked during removal but I re-used that.
Even though temps were hovering around freezing, the clutch roared and would not disengage even after the engine warmed up. I ordered a replacement kit to return that fan, and also a new cowling. The new clutch was a little less noisy (maybe partly the cowling?) but still have the same noise problem and the fan not really disengaged even at lower temps.
Most of my driving now is in the city, and I feel like the mpg (measured by the truck) has dropped from around 11-12 to 8-9. It does do a bit better with extended highway driving. I've been logging data (there are no DTCs), and the LTFT is mostly in the 6-8 range which seems a little high, though in spec. O2 sensors seem ok voltage-wise (first sensors rapidly oscillating between 0 and 0.9 V). There is a difference between banks 1 and 2 (1 LTFT is 1.6% higher at idle, 7.8 vs 6.2%). I did not see any exhaust leaks with the home-made smoke machine, but not sure how much I trust it since I was pumping into the tailpipe. Plugs and boots were new last summer. I haven't messed with the fuel injectors, and I ordered an intake gasket kit and new MAP sensor for cheap and easy insurance (neglected to get one when I did the plugs). AC is not currently working. While smoke testing the exhaust I found a nearly broken ground strap which I sistered across the damage with some new ground strap I had. At this point I only expect marginal, if any gains in fuel economy from going down this route, but maybe I will be surprised.
Since I am not doing a lot of hauling or 4-wheeling, I am tempted to put a regular duty, or maybe just heavy duty, fan clutch in to try to improve mileage. Neither is spec'ed for this vehicle, so I'm hesitant. The other choice is to try another manufacturer's severe duty, like a Hayden, but from the posts I've read I'm not sure that a different severe duty clutch would be any different. Any opinions or suggestions would be welcome.
TIA
Last edited:
