Lessons from a fan clutch...



Ever since I got my Fairmont (8 years ago), it had been plaqued with undercooling problems, especially on hot days. Even changing to a 3-row radiator didn't help very much. It also had disappointing gas mileage for a six.
After examining all kinds of (junkyard ) 200CID radiator fan setups, I decided to replace the thin-bladed 16" Ford flex fan with the setup from an air-conditioned Zephyr. This had a 17" non-flex fan with fat blades and a clutch that spaced the blades 2" from the radiator.
The change was dramatic. Instantly, the temperature was steady and low, even in long traffic tieups with my AC going, and the gas mileage went up over 1MPG (from 16 to over 17 in town).
About a month ago, the clutch started making noises and finally froze up solid (I've never seen one do that before; usually they lose their grip and won't cool). Available power dropped off so much that I could not even drive 70MPH and the gas mileage dropped into the 14's. I went to said junkyard again and nabbed a similar, but deeper, fan clutch from another Fairmont. This one worked OK, but spaced the fan just 3/4" from the radiator. This caused the engine to run VERY cool, too cool, in fact, and the gas mileage was still in the 14's.
So, off to the auto parts stores - finally, after 2 weeks of looking, I found that Ford made a Police Interceptor version of this 200CID six (!) in 1978 and 1979 Zephyrs. The fan clutch for these engines is the short-stemmed one I had stumbled onto in the junkyard. I got one (from NAPA) and installed it: the fan sits 2" from the radiator again. It cools just as well as when I first set it up this way again.
AND- I can run 90MPH, bumping over 18MPG in town, and the available power all through the engine's range is very noticeably better.

Thought I'd pass it along!
8) my grand marquis's fan clutch failed by seizing up, good thing to as i was about 75 miles from a parts store at the time.

I dont mean to criticize and god knows Im not an expert but the engine fan is to provide airflow through the radiator when there is not enough airflow to cool the radiator at stoplights or below 20mph. Above that airflow over the raditator should keep engine cool. And the fact that you had a 3 row radiator and still ran hot and couldnt make power at 70mph confuses me.

Im not denying what your saying but it seems to me that you might have other problems as well.
He couldn't make power because the fan clutch was seized causing the engine to try to spin the fan over 3K rpm at speed. Engine gets warmer because even though travelling fast, the engiine was working harder to try to spin that big fan.

The bigger-bladed fan created enormous drag when the fan clutch was locked up. The HP lost to turning the fan reduced top speed and gas mileage. While locked up, though, the engine ran VERY cool, too cool.

The distance from the radiator is also important. When the fan is close (like it was with the first replacement clutch) it creates much more drag than if it were further back. Granted, it moved more air through the radiator, but that was not needed. Moving the fan back 2" from the radiator (still inside of the fan shroud, though) reduced the amount of air, the drag and the noise. It also improved the physical airflow over the engine, cooling off the carb and reducing vapor lock (I live at high altitude where vapor lock is always a problem on carb'd cars in the summer).

Only bummer I've found about this is that it also improves DIRT flow across the engine, requiring more frequent underhood baths!