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Fan clutch or flex fan?



What is everyones opinions regarding fan clutches vs flex fans?

Hubby has replaced the fan clutch four times in 11 years and think this is excessive.

noisy flex fan

While at risk of appearing to whine too much, I think flex fans are EXCESSIVELY noisy (LOL).
too many fan clutches

Ken thinks four fan clutches in eleven years is excessive ... I know this is far too much for a relatively stock daily driver. Who has been determining the clutches have failed ... and what's been the test criteria? If there's been four true failures in such short order ... could it be that the fan is bent / cracked / even missing a blade ... causing an imbalance?
fan failure

Hubby says the fan is fine, it has been a bearing each time.

My understanding of fan clutches: Hand spin easily when cold, hand spins with resistance when engine hot. Turn engine off and fan should spin a few revolutions before stopping. I believe the fan works by temperature, as the engine heats up, the fan clutch tightens and spins the fan more effectively.

Last week I removed my smog pump belt because of the noise I was hearing under the hood, a rattley grinding whine. With the engine off I hand turned the smog pump and could feel the resistance and hear the bad bearing inside. However I am still hearing a high whistling whine under the hood. Belts are relatively new and not worn, with proper tension. I'm not using my AC regularly, ps (entire system) is new and what else do I have except the alternator? Battery charges and holds its charge just fine.

Hmmm ... ya got me!

Other than to take another close look at fan; also checking for loose blade-to-hub rivits ... I'm pretty much at a loss.

Do new clutches' pilot hole inside diameter closely match the OD of the water pump's pilot stub-shaft? Same goes for center hole in water pump pulley. I'm referring to a difference/mismatch between a possible 5/8" shaft and possible 3/4" hole. But, I'm still thinking there's a possible rotational imbalance.

Are the blades hitting, or have they been hitting the fan shroud? The dynamics may not be either audibly or visibly apparent while either running or engine off; may require close shroud/blade tip inspection.

Rubber motor mounts eventually turn to goo with age, heat & oil (any petro-solvent). With loose/worn motor mount(s), motor can perambulate, permitting blades to contact shroud / air filter housing to hit hood. Maybe not enough contact to clearly damage blade tips... but enough to overstress the clutches' bearings. I'm at the limit of failure mode analysis without further inputs ... other ideas guys?
I just had my car on the dyno recently. On the last run we pulled the fan clutch to see how much power it was using. The difference with fan clutch removed was nearly 15hp and 10 ft-lbs of torque. That is quite a lot not to mention the gas it is using up. My machine shop guy who does the dyno testing suggested converting to dual electric fans. Will give best cooling while using very little power. Until I can budget that in with the 30 other projects on this car, he suggested the Flex-A-Lite 400 series fan which only cost $15.00 from Jegs. He has dynoed(sp?) many fans and said this one works the best. I really trust this guy as he used to race here in Charlotte and comes highly recommended from several local racers. Just a thought.


fan shroud

When hubby purchased the car 11 years ago, an upper part of the fan shroud was cut away...I am assuming the fan had been hitting the shroud at some point. Motor mounts were replaced about 93 or so, and again with the new engine in 97, when I also replaced the modified shroud and put on a complete one. I don't know what else we can check...?
Something will crop up, it always does....:D

Whining noise


The only way to find out what is making that noise is to open the hood and stand it front of the car while someone revs up the engine. Check each component to see where the noise is coming from. You may have to remove some belts to eliminate some possibilities, such as alternator or power steering. One thing I've found out over the years.....these things never fix themselves.

Be careful,
I had the clutch fan sieze and break apart one day.. One piece went through the hood, one through the lower rad hose and one put a tiny little dent in the fuel line. I put flex fan on it and noticed a power increase, but the noise wasn't too bad. I would go with electric fans these days, though.
I understand, that you should never place a clutch fan in a horizontal position for too long. They should be stored at the parts place in a vertical (as installed) position. Something about the silicon inside of them running to the wrong places.
Go electric. Flex fans are too loud.
We just put a Imperial Flex fan and Spacer kit on the 62 as the stock clutch fan was not cooling enough at idle speeds

I have to say that we haven't seen any difference in the noise, not even the whine some folks report. It has also made about a 15 degree difference at idle and does a much better job of keeping her cool overall.:upthumbs

Total cost $32 dollars..
Rick and Donna:

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