How can I tell if my Fan Clutch is dead or dying
- Thread starter Morales
- Start date
There seem to be a lot of electric fan guys on here, but my info is that no electric fan can actually match a mechanical for airflow. They simply don't move as much air. Assuming that's true, my thinking is that you should not make the jump to electric unless you are moving up to a better radiator too.
As to fan clutches, the best test is to compare the number of revs before it stops on shutoff cold versus hot. Cold engine (after a suitable warmup, since the juices inside the clutch must still get up to temp), and the fan should continue to freewheel for half a dozen or more revs on shutdown. But get the engine good and hot, and with high ambient air temperatures, and the fan should snap to a halt one or two revs after shutdown -- almost instantly. You'll see it -- just look. Fan clutches also seize, causing constant lockup, but that is characterized by a constantly cold temp gauge, and a constant whoosing sound with the fan moving maximum airflow even when cold.
The last point is that in my experience with more than a dozen fan clutches, is that aftermarket ones are universally too tight, costing HP. Most people looking for a new fan clutch get there because of overheating, and I guess the aftermarket makers figure a little tighter is better than a little looser. But you can really feel the difference between a too-tight fan clutch and one that works right in the seat of your pants. Just pull the fan belt when the clutch is locked up and go for a quick blast -- you'll feel a big difference. My personal opinion, and recommendation, is to go with a factory Ford fan clutch, even if it costs twice as much money. They simply seem to work better, consistently.
Just my opinion (after 6 small block Fords, 4 of which were 5.0 cars).
As to fan clutches, the best test is to compare the number of revs before it stops on shutoff cold versus hot. Cold engine (after a suitable warmup, since the juices inside the clutch must still get up to temp), and the fan should continue to freewheel for half a dozen or more revs on shutdown. But get the engine good and hot, and with high ambient air temperatures, and the fan should snap to a halt one or two revs after shutdown -- almost instantly. You'll see it -- just look. Fan clutches also seize, causing constant lockup, but that is characterized by a constantly cold temp gauge, and a constant whoosing sound with the fan moving maximum airflow even when cold.
The last point is that in my experience with more than a dozen fan clutches, is that aftermarket ones are universally too tight, costing HP. Most people looking for a new fan clutch get there because of overheating, and I guess the aftermarket makers figure a little tighter is better than a little looser. But you can really feel the difference between a too-tight fan clutch and one that works right in the seat of your pants. Just pull the fan belt when the clutch is locked up and go for a quick blast -- you'll feel a big difference. My personal opinion, and recommendation, is to go with a factory Ford fan clutch, even if it costs twice as much money. They simply seem to work better, consistently.
Just my opinion (after 6 small block Fords, 4 of which were 5.0 cars).
Sam, you make some good points. I disagree on airflow on mechanical vs electrical somewhat though. You can get electrical fans that pull more air than your average mechanical fan, but the downside is they draw a ton of amps and are hard on the charging system unless you use something like a DC Control unit.
That being said, I think people get caught up on airflow a bit much. IMO, it's better to have a bit less CFM, but the fan covering more surface area on the radiator, than to have a higher CFM fan that only pulls air through a smaller concentrated area. This is one reason why I went with the dual ramcharger setup. The dual 11" design simply covers more area of the radiator then the OEM mechanical fan, or any of the common aftermarket single fans. The fact that it's a heavy, solid OEM fan made by Valeo is a plus too, not to mention the price.
It also depends on a ton of variables too. A heavily built motor that is in a car with A/C and operated in a warmer climate is going to have different cooling needs than a mildy built H/C/I car with no A/C in a cooler part of the country.
In my case, I'm upgrading my whole cooling system, and tearing out the A/C system at the same time on my daily driver. I am upgrading to a larger 31" x 19" x 3" Griffin aluminum radiator, as well as the RC fan. This particular setup is major overkill for my daily driver up here in New England where we only get 80-90's a month or two a year. I've never had any overheating with the stock setup and edelbrock water pump anyhow, but I also run a 16 row oil cooler, so that helps as well. In my case, the factory fan is starting to crack, and the clutch is going, so upgrading to the Griffin for $189, and the RC fan for under $100 is money well spent over just replacing the factory fan blade/clutch.
One other plus to an electric fan is that it puts much less wear and tear on your water pump, but this isn't a huge issue. I think there is really no way to say a electric or mechanical is "better" across the board...it's like most things...there are pro's and cons to both.
Anyway...that's just my (very long) .02...
That being said, I think people get caught up on airflow a bit much. IMO, it's better to have a bit less CFM, but the fan covering more surface area on the radiator, than to have a higher CFM fan that only pulls air through a smaller concentrated area. This is one reason why I went with the dual ramcharger setup. The dual 11" design simply covers more area of the radiator then the OEM mechanical fan, or any of the common aftermarket single fans. The fact that it's a heavy, solid OEM fan made by Valeo is a plus too, not to mention the price.
It also depends on a ton of variables too. A heavily built motor that is in a car with A/C and operated in a warmer climate is going to have different cooling needs than a mildy built H/C/I car with no A/C in a cooler part of the country.
In my case, I'm upgrading my whole cooling system, and tearing out the A/C system at the same time on my daily driver. I am upgrading to a larger 31" x 19" x 3" Griffin aluminum radiator, as well as the RC fan. This particular setup is major overkill for my daily driver up here in New England where we only get 80-90's a month or two a year. I've never had any overheating with the stock setup and edelbrock water pump anyhow, but I also run a 16 row oil cooler, so that helps as well. In my case, the factory fan is starting to crack, and the clutch is going, so upgrading to the Griffin for $189, and the RC fan for under $100 is money well spent over just replacing the factory fan blade/clutch.
One other plus to an electric fan is that it puts much less wear and tear on your water pump, but this isn't a huge issue. I think there is really no way to say a electric or mechanical is "better" across the board...it's like most things...there are pro's and cons to both.
Anyway...that's just my (very long) .02...
i never heard of any of these methods to check a fan clutch from what i read here. the way i was told and which seems to work great is to spin the fan by hand(engine off of course). the fan should not spin around more then once. if you spin the fan and it goes around several times before it stops, then the fan clutch is worn out.
I still believe that mechanicals move more air. Witness the Chevy B-Body/Impala SS. All 94-96 B-Bodies, including the SS and 9C1 cop cars, came with dual electrics. They also had separate transmission and engine oil coolers on every car. But if you wanted a towing package, Chevy went to a mechanical belt driven fan, which was no simple matter since the water pump was gear driven off the cam's timing gear. They had to manufacture a whole separate bracket, shroud, and add an additional belt and pulley setup to make it work -- a signifcant change. But for them that single change upgraded the towing capacity something like 8,000 lbs.
Another thing that highlights is the fact that mechanical fan cars have all had fan shrouds since the 70's, which means that almost the enitre area of the radiator is put to work. By contrast, I have seen almost no electric fan cars with similar shrouding.
Don't get me wrong -- electrics are great. I switched my '94 Caprice/Impala SS clone car from mechanical to factory electrics, and got a signifcant seat-of-the-pants improvement in acceleration. But it didn't cool as good as the mechanical -- even after I went with a 160 thermostat (not too cold for a reverse-flow cooling system LT1) and reprogrammed the computer to kick the fans on at 180. I ended up going to a bigass Becool aluminum radiator to make up the difference.
Again, just my experience and opinions -- I think you need a bigger radiator in a Mustang in any case, but it is all the more true if you go electric.
Another thing that highlights is the fact that mechanical fan cars have all had fan shrouds since the 70's, which means that almost the enitre area of the radiator is put to work. By contrast, I have seen almost no electric fan cars with similar shrouding.
Don't get me wrong -- electrics are great. I switched my '94 Caprice/Impala SS clone car from mechanical to factory electrics, and got a signifcant seat-of-the-pants improvement in acceleration. But it didn't cool as good as the mechanical -- even after I went with a 160 thermostat (not too cold for a reverse-flow cooling system LT1) and reprogrammed the computer to kick the fans on at 180. I ended up going to a bigass Becool aluminum radiator to make up the difference.
Again, just my experience and opinions -- I think you need a bigger radiator in a Mustang in any case, but it is all the more true if you go electric.
SamSnyder said:
The Ramcharger fan I was speaking about has it's own shroud, as do most electric fans. I think you are assuming they don't because they aren't as large as with a mechanical fan. If they didn't come shrouded, they wouldn't be very effective...
Also, I do agree with you on surface area, which is why I mentioned a dual fan setup offers more coverage than any single fan setup. I'm using a 39' x 19" radiator, and the RC fan covers ~30" x 16"...that's almost the entire surface area...
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