Mechanical cooling fan power consumption

[Truckedup]

I haven't had a 'thermal' fan clutch die and lock up, yet. But I have had one go totally soft, at temp, and the blades barely coasted. After cooling it down with a garden hose to the radiator at an idle, I shut it down and pulled the old solid mount 4 blade out from under the seat. Bolted it on and all was well again. This was early 70's, not a lot of thermal clutches, yet.

It was a noticeable power difference.

I soon bought a new thermal clutch unit.

According to manufacturers who make them, viscous drive fans have a lifespan and will "slip" more with the passage of time...I've replaced a few when the vehicle started to run warmer at low speeds and problem solved.

[OILEAKY]

http://www.haydenauto.com/upload/Hayden ... 980012.pdf

The above is a quick education in fan clutches.
Worth the read.

[psychomotors]

http://www.haydenauto.com/upload/Hayden ... 980012.pdf

The above is a quick education in fan clutches.
Worth the read.

Very good read indeed. Thanks.

[upinthehills]

If your engine is working properly along with a good cooling system, you don't even need a fan so long as you're moving.

This isn't much help but for a street car maybe useful. Many years ago went to a Rolling Stones concert. Leaving the venue very late at night I noticed the lights were quite dim. Told the driver to turn off the headlights and drive right up behind the other traffic so we could see where we were going. Drove a couple of hours on the interstate right up behind an 18 wheeler.

Next day we look under the hood and the fan belt was missing. The mechanical fan got enough horsepower from the air stream to keep the engine cooled. It was a Mustang II with a 2.3L. That night the mechanical fan was well worth it.

[panic]

The mechanical fan got enough horsepower from the air stream to keep the engine cooled

It was free-wheeling in the air stream. The forward motion provided 100% of the cooling.

[MadBill]

Smokey Yunick experimented with a fan-driven generator at Daytona one year..

[Schurkey]

The mechanical fan got enough horsepower from the air stream to keep the engine cooled

It was free-wheeling in the air stream. The forward motion provided 100% of the cooling.

The point--as I understand it--was that the airflow turned the fan, WHICH POWERED THE WATER PUMP. So, yeah, the fan was deriving power from the airstream, not merely the airstream cooling the radiator.

I could be wrong--I forget how the Pinto 2.3 drives the water pump--maybe the pump turns based on the timing belt.

[Truckedup]

Like some of you perhaps, My 64 Chevy with a 327 would turn the fan belt inside out or toss it at high rpm's....When the belt came off the engine heated up quickly even at higher speeds....So I guess it was the damn clutch fan slipping and not turning the water pump by airflow...

[BCjohnny]

According to manufacturers who make them, viscous drive fans have a lifespan and will "slip" more with the passage of time...I've replaced a few when the vehicle started to run warmer at low speeds and problem solved.

Completely OT but ...... I know one professional mechanic (ret.) who once repaced a manual gearbox due to 'excessively noisy bearings' and upon road testing the noise was just as bad. Turned out to be a worn 'viscious' fan resonating through the drivetrain

He of course replace the fan FOC as a courtesy to the customer.

[peejay]

The mechanical fan got enough horsepower from the air stream to keep the engine cooled

It was free-wheeling in the air stream. The forward motion provided 100% of the cooling.

The mechanical fan was driving the water pump, powered by airflow.

I did had to do this once, it really does work.

[upinthehills]

Back in those days when you could actually see the motor with the hood up the whole story was right there when I looked. A little metal fan bolted to the front of the water pump. After we got off the highway ( at least a hundred miles ) it was probably nearly 3 in the morning. With no traffic it did fine driving thru town until we got home.

I don't think the water pump draws a lot of power. A friend who is building a tube frame car, something like a cross between a Lotus 7 and a late Indy roadster, decided to use an electric water pump and fan. He showed me the numbers and I was surprised the fan drew 2 or 3 times as much power as the water pump. The water pump doesn't really need any pressure though it just pumps the water around in a circle...

[dave brode]

The Model T did not have a water pump until late in the T's run and I believe that even then it was an option.

[roc]

The Model T did not have a water pump until late in the T's run and I believe that even then it was an option.

The DKW engine didn't have water pump either, water flow was provided by thermo syphon. https://commons.wikimedia.org/wiki/File ... e_Luxe.JPG

[RWILLIAMS]

On my sons circle track car we went to a 2 blade fan after we went to e85 I know it picked up some power how much I do not know .It races at 200 degrees on the hot nites. I think it pulls as much air or more than the 4 blade fan we were using.

[peejay]

I don't think the water pump draws a lot of power. A friend who is building a tube frame car, something like a cross between a Lotus 7 and a late Indy roadster, decided to use an electric water pump and fan. He showed me the numbers and I was surprised the fan drew 2 or 3 times as much power as the water pump. The water pump doesn't really need any pressure though it just pumps the water around in a circle...

My top speed went up 5mph just by draining the coolant out of the engine. I was running late and the radiator leak went bad and the car owed me nothing, so I just went for it and bolted the throttle down. It was great until it started overheating and binding up and losing power.

You may be surprised how much head pressure a water pump can generate. And how much power they suck if you overspeed them and cause cavitation in the impeller!