1995 Honda Accord boils over

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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.
--
Jim Yanik
jyanik
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Jim Yanik wrote:

by "flatten out" do you mean a variable pitch fan blade? that's somewhat exotic and rather expensive. what used them?

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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!
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Hachiroku $B%O%A%m%/ wrote:

just because it's plastic does not mean it's flexible enough to "flatten out" as if it's variable pitch. what mechanical properties do /you/ think "flexibility" gives the fan?
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On Wed, 02 May 2007 22:34:13 -0700, jim beam wrote:

Who cares?
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Hachiroku $B%O%A%m%/ wrote:

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.
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jim beam wrote:

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 windmilling mode.
I never had any confidence in these "devices."
JT
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Grumpy AuContraire wrote:

agreed!
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I don't think they can inhibit air flow that way because the air pressure against the blade is what flexes them "flatter." At least in theory, they should still be pushing air.
To each their own.
Mike
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Michael Pardee wrote:

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 price...
JT
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http://www.flex-a-lite.com/auto/html/7-blade-flex.html
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Michael Pardee wrote:

did you know that the outer extremity of a fan blade moves faster than the bit nearest the hub? apparently these guys don't since it's the same pitch for the whole blade!!! what a total p.o.s.
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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!)
Mike
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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.
Mike
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Michael Pardee wrote:

interesting - i've never seen a fan like that. seems kind of bizarre to me since i can't see what would keep the blade pitched to improve airflow when it was supposed to be working, but hey...

indeed.
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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.
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Hachiroku $B%O%A%m%/ wrote:

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.
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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.
Mike
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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 overheating problem.
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...
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On Apr 29, 7:41 pm, snipped-for-privacy@gmail.com 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. MK
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