Autos use electric fans purposely so they don't have to draw engine power
to turn the radiator fan when it's not needed;when the vehicle is at speed
and there's plenty of natural airflow.
The old belt driven fans changed to plastic blades because they could
flatten out at higher speeds and draw less power from the motor.
Electric fans were just the next step after that for economy.
On Wed, 02 May 2007 21:29:25 -0700, jim beam wrote:
My Supra has one. Also a Celica I had ('85) and an '85 Corolla.
Most of the fans post 75 or so are plastic, one reason being weight and
the other being the flexability of plastic. I can't remember the last time
I saw a metal fan!
you should if you want the fan to move the freakin' air that you think
is cooling your engine!!! if the blades can adopt a position of least
resistance, they will. that means throughput will be minimal - totally
defeats their supposed purpose.
I would be inclined to think that these fans could actually inhibit
cooling during high speed driving as the "flattened" fan blades would
act muck like a feathered prop in the wrong position which then enters a
I never had any confidence in these "devices."
Nope, the higher the RPM, the greater deflection of air, almost like
having a circle of plywood right in back of the radiator.... So much
so, it could become a negative factor at higher rpms. "Silence" has a
You're right about the change in air speed and that the ideal pitch should
vary along the blades like the pitch on an airplane propellor or a ship
"screw." This isn't rocket science, though, it's just a radiator fan they
are trying to improve a bit. Regular fans work and these fans work. Take
your choice (I think you already did!)
I don't know whether they were ever used as OEM fans, but my motorhead
brother was pretty fond of aftermarket "flex fans." If the plastic blade is
mounted to the hub by the leading edge, it's a good bet it is a flex fan. If
the blade is mounted by the whole root it is just another fan.
On Tue, 01 May 2007 20:43:23 -0700, jim beam wrote:
Check my response to Mike, above.
I was also running without the shroud underneath the engine, and while
replacing it helped somewhat, it wasn't until I replaced the clutch that
the problem disappeared.
around town, sure. but not on the freeway. lack of shroud, insect
debris blockage, kinked coolant pipe, slipping belt on coolant pump, out
of spec thermostat - these all have much more effect at freeway speed.
How about the front of the water pump? Viscous fan clutches were very
popular in the '80s. They worked pretty well when new, but the silicone
tended to leak out over the years. They would become progressively less
effective and the driver wouldn't know until the situation got really bad.
On Wed, 02 May 2007 03:43:10 -0700, Michael Pardee wrote:
DING! DING! Mike wins the prize! Exactly what happened in my Supra.
I have the records from the old owner. She spent $1100 traking down an
The first year I had the car, the temp barely got over 90 degrees all
summer. Plus, we did a timing belt and the car had all new coolant in it.
It never overheated.
Last summer, we had a lot of days over 90 degrees, and it was on these
days it was most likely to overheat. I asked the guys in the Toyota forum
and a former Service Rep gave me a method for checking the fan (basically,
get the car up to temp, stop the engine and try to spin the fan...mine
spun with no resistance at all.)
New fan clutch, no overheating! I did notice the previous owner did not
install a new clutch...
On Apr 29, 7:41 pm, firstname.lastname@example.org wrote:
Sounds like you need a new radiator to me..
I'm not so sure about the head gasket..
Maybe, but I still think your radiator is about
shot. A leaky head gasket will not cause all
the symtoms you have. IE: overheating...
The only way a head gasket causes overheating
is when it finally loses it's coolant.. If it's still fairly
full when doing this, I doubt the gasket is the problem.
Most of your problems sound like a bad radiator.
Thats why it overheated in the first place I bet.
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