Clutch fans

Can a broken one cause a loss in power and mileage?

Mileage for sure (especially if it's overcooling the engine), maybe a little power. If the clutch is seized, you'll hear it roaring as the revs build.

yes,

Assuming you are talking about engine driven fans, and not people who are fans of clutches.

Clutched fans are designed so that IF they fail, it will be in the on position. And the loss in power and mileage is a strong illustration why it was clutched in the first place.

I've never had one fail stuck. Mine always fail free spinning, resulting in poor cooling at stop and go traffic. I suppose it could rob a little power. That's why it's there: to free up power when the fan isn't needed.

I'm a clutch fan

In reply to Dr. Hess:

interesting failure mode.... i would do my best to make it fail on, to prevent it from over heating....

Anyway, one might be surprised how much power it takes to spin a modern big bladed fan- I know older ones were in the 10-15hp range at rated peak power speed. It takes a whole lot of energy to move that much air.

all I can add.. I knew a mechanic who could reach into the fan on a running car and grab the fan, stopping it.

He was always a bit crazy

In reply to mad_machine:

I've done that with a bad fan clutch. Grab it and spin it backwards. Not brave enough to try it with a good fan clutch.

Bearing took a dump on me. Cooled fine but when cold, it would make noise. Warmed up, no noise.

Taiden wrote: I'm a clutch fan

Yeah, when I first saw this thread I thought it should've been OT.

alfadriver wrote: Anyway, one might be surprised how much power it takes to spin a modern big bladed fan- I know older ones were in the 10-15hp range at rated peak power speed. It takes a whole lot of energy to move that much air.

A very popular mod on the Canyon/Colorado forums is installing an electric fan. Between that, and a few other (very) minor mods, they're getting decent horsepower increases.

The fan clutch on my e36 was stuck engaged. After I replaced it I gained 7mpg on the highway. I could never get it above 25 before no matter what. Now its always between 30-33. Not to mention the power increase. I still cant get over the difference it made.

I had a hard time to convince the driver of our modified that we should remove the engine driven fan, no clutch, and install an electric fan. He was very happy with the increased power.

Ty_Lo95 wrote: The fan clutch on my e36 was stuck engaged. After I replaced it I gained 7mpg on the highway. I could never get it above 25 before no matter what. Now its always between 30-33. Not to mention the power increase. I still cant get over the difference it made.

That is what I have going on. No matter what I do, 19-19.5mpg, 200-210 miles on 10.5-11 gals. Few months back, I could get 21-ish if I really tried. BTW, revised EPA numbers are 13/19 or 20. berkeleying Chrysler product.

Ty_Lo95 wrote: The fan clutch on my e36 was stuck engaged. After I replaced it I gained 7mpg on the highway. I could never get it above 25 before no matter what. Now its always between 30-33. Not to mention the power increase. I still cant get over the difference it made.

That's incredible.

92CelicaHalfTrac wrote:

dammit, you beat me to it.

they are indeed epic, especially live.

I pulled the clutch fan and the stock aux fan from my e30. Removing the stock aux fan took about 15lbs out of the nose of the car. Removing the clutch fan let the engine rev much better, feels more powerful by the butt dyno, and is sure a hell of alot quieter at idle (my clutch on the fan seemed to work sometimes, but not all the time).

Replaced with a 14" SPAL low-profile puller bolted into the stock clutch fan shroud, wired to an 80* thermo. Car runs slightly below middle on the temp gauge, and sitting at idel in the rallycross grid it gets under 3/4 before and then the fan kicks in and gets it back below half.

~25lbs gone from the nose, and parasitic drag gone from the motor. No idea why anyone would keep the original fans anyhow. First project on the GT6 this summer will be to ditch the stock fan as well.........

Iff'n y'all go back into the olden days, say when I was a teenager and 280Z and 710 Datsuns were new, it was not unusual at all for fan clutches to seize in the "on" position. It was also not unusual for the force of the drawing air to pull the fan and clutch off the shaft of the water pump and fire them through the radiator.

I have always recommended strongly to change them when they fail.

I had stated this before:

I had a 84 chevy 350 auto 3 speed 2wd with a Qjet.

Highway MPG Clutch fan: 19.7 No fan: 19.7 Electric fan: 19.7

Seriously. Clutch fans rock. I've had two fail ever, and they both failed locked. I, too, have grabbed a good one while the engine was running for fun.

I would'nt expect the mileage on an L83 to be affected by whatever type of fan it uses (clutch, none, electric, etc)

But for those of us with little 100hp engines, that's a different story, haha.

A quick search of the BMW forums will turn up multiple accounts of the fans on the V8s locking up and exploding (speculation is that this is due to bad motor mounts allowing the overspeeded fan to hit the radiator). This sends shrapnel all over the place, including in at least one documented case through the hood.

The previous owner of my car let it go long enough that the fan grenaded. It sliced the radiator hoses and left a gash in the hood insulation. My good friend that had the car before me replaced it with another fan that stayed engaged (the one that I finally just replaced). The car sits at over 3k at highway speeds. It was only a matter of time in those circumstances that something gives out. The difference was night and day as far as power and how the engine revs.

Hmm makes me want to do a proper electric fan conversion on my Samurai, it could help make up for the power loss of running locked manual hubs in rallies...

this on e36 as well. removing the stock fan is called a fdm fan delete mod. most already have an electric aux fan so people just add water wetter. In reply to 02Pilot: