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Fan clutch

3K views 23 replies 15 participants last post by  techinspector1 
#1 ·
Hello all
Another dumb question !!!!

Do I really need a clutch on my fan? I have a bad space problem between the radiator and fan . There is no room for a clutch.
What are the pro and cons of not having one .
Thanks

Jeff
 
#22 ·
4%, ok.. sure.. you do know a mechanical clutch fan take zero hp until needed, most times in traffic.. not at cruising speeds..
4% is a small amount. A clutch fan creates additional parasitic loss 100% of the time, not fully engaged does not mean 0 power is being wasted. Also, the engine will warm up faster with an electric fan vs a clutch fan, this saves additional fuel.

http://ecomodder.com/forum/showthread.php/electric-vs-belt-driven-cooling-fan-3365.html


1998 Mercury Mountaineer electric fan MPG increase. - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

Is an Electric fan conversion worth it? My testing procedure - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
 
#10 ·
Do you _NEED_ a clutch? no.
do you _WANT_ a clutch? yes.

like it was mentioned.. power, economy, and yes.. NOISE and lots of it..

and also like it was suggested, electric fans are the way to go.

this is my ultra low dollar electric fan setup :)

http://home.comcast.net/~kc8oye/Engine/DSCN1143.JPG

as you can see, space isn't a concern.. but I was having problems with cooling with the pos flex fan that was in there when I got the car, I was given the large electric fan (stock GM piece to something from the 80's) so I went straight to electric. I added the little 10" fan when I found the engine heat would tend to climb slowly when the air temps were really high (like 95° and higher)

as it happens, the big fan is a two speed.. and after playing around with different configs, I found the setup I liked the best, was that both fans turn on @ 190F with the big fan on low. the big fan comes on 'high' @ 200°F
(I run a 160 t-stat, so this way, most of the time, the fans don't even come on unless I'm sitting still for a LONG time)
that big fan is REALLLY noisey on high, so I have it setup as an 'oh crap, it's getting hot' :)
 
#11 ·
There are several common challenges with converting to an electric fan:
- You need to figure out what fits, and often you need to fabricate some type of shroud to make it more effective. It sounds like you already have space problems, so you will need to take some careful measurements.
- Some of the most effective fans (e.g. the Lincoln Mark VIII electric) draw quite a bit of power, especially as they kick on. You need good quality relays and wiring.
- Specs on aftermarket fans are not that reliable. Every manufacturers quotes an air flow rate, but its difficult to compare them directly. Some relatively inexpensive fans work just as well as the very pricey ones.

Bruce
 
#13 ·
Downside to running a clutch fan is that the fan only runs when you are moving slowly. As the rpms pick up the fan actually stops spinning or spins very slow. I never liked them because of the added weight on the pump snout. I have a better pitched 6 blade fan on my car and it spins all the time and does not make anymore noise than a clutched one would.
I also had a clutch fail on a fan years ago on the road......then you have problems.
 
#14 ·
Downside to running a clutch fan is that the fan only runs when you are moving slowly. As the rpms pick up the fan actually stops spinning or spins very slow.
Ah...

That's kinda the whole point of a clutch fan. It only engages the fan (and increases the noise and HP loss) when the fan is needed. Why is that a "downside"?

As for the weight of the fan, the load that the added weight of the fan puts on the water pump bearing is far less than the load from belt tension. Consider that pretty much any engine you would plan to run a clutch fan on came with one from the factory, so the water pump is already designed for it.
 
#18 ·
I've had brake lines rupture, starters fail, and tires go flat, so by your logic, we should all go back to mechanical brakes, hand-crank starting, and solid rubber tires...

Maybe we should all just drive soap box derby cars.

OK, seriously, I agree with your premise to keep things simple, but there is a tradeoff. Yeah, I've had a fan clutch fail, but usually you can see the silicone fluid start to leak BEFORE it fails completely. Mechanical parts wear out and break. That is a fact of life. Yes, if you don't have a clutch, it won't fail, but running a clutch allows you to run a fan that pulls more air for cooling without paying the penalty in noise or lost HP. I trust electric fans a lot less than a fan clutch. In 40 years of driving vehicles with fan clutches, I've had exactly one failure on the road, and in that case it actually failed in the locked up position, so it still cooled, it just made a lot more noise.
 
#19 ·
Hayden - Fan Clutches and Fan Blades

Theres a good primer on Hayden clutches (both thermal and non) and the amount of pitch to the fan blades; from 1.5" to 2.5"+
Ive always preferred a good quality clutched fan. I had one fail along time ago on a truck (1974 C20 w. 350 v8) with 200k miles or more (farm truck). Went down to Napa and they had one on the shelf; standard rotation, thermal clutch, Heavy Duty and it was less than 30 bucks. If you have a street rodder electric fan and you burn it up in Sweaty Armpit, Oklahoma on a Saturday...what do you do? Even a non-thermal clutch for $20 will get you home, it'll just be loud and probably last 20,000mi as opposed to 50,000mi
 
#21 ·
I have nothing against clutch fans,
Ive had 1 failure and seen only a couple
worst one was on a 327, 57 chevy.
fan let go and chopped off trans cooler lines damaging the rad beyond repair (glad it did not go through the hood)
high/quick revving engines tend to toss the belt often,especially old style with alternator/generator on the left side
Ive seen quite a few fibergalss fans break after 1 or 2 years
belts get chopped by steel fan blades and seem to break fiberglass blades
heavier clutch fans seem to have more belts jump
I guess the shorter belt system and/or deeper pulleys have a use
 
#23 ·
do not forget that a non-clutch fan, just like an electric fan that is running.. will become an IMPEDIMENT to air flow...

if the air coming through the radiator is moving faster than the fan could move it by itself, the fan actually becomes an obstruction. that's why leaving electric fans hardwired on is a bad idea. This is also why we have clutch fans.. it allows the fan to over-run the engine speed..

my electric fans are set to come on @ 190F.. with a 160 t-stat, with the temp sensor in the radiator. so as long as I'm moving enough to keep the radiator doing it's job, my fans don't run. they only come on when I've been sitting still for a few minutes..
 
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