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Hello...still plenty of snow up here in ND! I have a 1977 F100 2wd with 302. The original fan is four blades. I want to try a fan clutch. My thinking is, with a clutch, my engine will warm up faster in colder weather as I drive my pickup year round. I bought a used 5 blade fan and clutch and installed it last night. It was in the 30s ambient temp. wise. It definitely warmed up the engine faster, but when I went on a road test, my pickup ran warm--not to the point of overheating but warmer than I'd like considering warmer weather will come...eventually. I did notice the 5 blade fan and clutch was much heavier than the aluminum spacer and 4 blade. Maybe a different water pump is called for?? Appreciate any insights. Thanks!
You're right; if the only thing you changed was the fan, and it ran warmer, probably it was the fan that caused it. If the ambient was in the 30s, it's best to get it fixed before summer. As Dave said, be sure it is configured correctly. The next thing to be sure about is that the clutch is engaging properly. It appears that there were 18" & 19" fans used on your engine. Be sure it "matches" the shroud correctly. Also there are "thermal" and "non-thermal" clutches available. Get everything configured correctly with a clutch that works properly, and it should do what you're after.
Thanks guys! The 4 blade factory fan is 17". The shroud has 19" diameter. I made sure the 5 blade and clutch sits halfway into the shroud. The 5 blade is just barely bigger in diameter than the 4 blade. I didn't realize that clutches might spin the fan the wrong way. How easy should it be to turn the fan by hand if the clutch is working properly? Also, the clutch I have had the spiral spring in front, so I believe it's thermal. Mine is a non-AC pickup and the fan clutch wasn't standard from the factory.
Last edited by msalander; Apr 23, 2023 at 11:19 AM.
Reason: missing information
@msalander it sounds like you accomplished your goal, the truck warms up faster and gets warmer because the airflow is different. It's not constantly blowing cold air over the engine and radiator. It's hard to assess if the fan is not working as intended because you have 30 deg ambient still. The fan clutch can't make the fan spin backwards, but the fan could be made for reverse rotation depending on what you got it from.
The thermal clutch likely won't really engage until the truck is over 200 degrees, and near that coming off the radiator. If it has some resistance spinning by hand it is probably fine. If it spins like the wheel of fortune it's not. Depending on the duty rating of the clutch, it will be 30% engaged when the thermal is off and 70% when the thermal is on, and the clutch is designed to release as rpms get higher, from what I've noticed over 3000 rpm.
Again, thanks guys! Upon further research and observation, my fan clutch (when you look at the thermal spring side) has a 'R' with a counterclockwise arrow. A couple sites mentioned serpentine systems used counterclockwise clutches while the v-belt systems (like mine) rotate clockwise. When I started my pickup, looking from the radiator to the firewall, the stock fan rotates clockwise. I'm assuming the fan and clutch should turn in the same direction, right?
@msalander yes, but you need to make sure the fan will push the air in the right direction too. Note the way the blades are angled in this pic. Because a fan clutch pumps the internal fluid against the working surface it does need to rotate correctly.
Ol' dummy here is finally beginning to understand! What your saying is the counterclockwise clutch I have goes with a counterclockwise fan! D'oh! I'm assuming in your picture, the fan turns clockwise? Thanks again!
Correct. 99% of the time a v-belt drive turns clockwise. If the water pump is driven off the back side of a serpentine belt, it's most likely counter clockwise.
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