Fan Clutch

[rmp243]

How can I tell if my fan clutch is bad. I was told when the car is cold there should be some resistance turning the fan. It that correct?

Thanks
Rob

[showbizkid]

You might want to try searching for "fan clutch", there was a thread on this just recently with some off-site links that were pretty useful.

Long story short: If the clutch isn't leaking fluid, can't be wiggled up-and-down or side-to-side on the shaft, and does not revolve for more than 3 revolutions after the engine stops, it's OK mechanically. If it's a thermostatically-controlled fan, there are other tests for determining if the thermostat is OK.


[img=left]http://members.cox.net/clarknovak/lark.gif[/img=left]

Clark in San Diego
'63 F2/Lark Standard
http://studeblogger.blogspot.com
www.studebakersandiego.com

[rmp243]

I will try that out. I just been having some strange over heating issues. If I needed to flush the block out do I need to pull the core plugs out to accomplish this or is the a drain plug on the block itself. Kind of problem I am having is the car will run at 180/190 and then all of a sudden jump past 240 in matter of seconds. I pulled over open the hood and then all of a sudden the temperature drops. I have replaced the thermostat but did not flush the block out. I also used an IR sensor tool to read the temperature when hot and I get a reading of 190/195.

Rob

[showbizkid]

There could be a couple of things going on here. It could be that there's some floating debris in your water jacket that's blocking things up. To flush the block you need to pull the core plugs AND the pipe plug at the back of the block. Instructions are here in the section marked "The Cooling System."

Another thing that occurs to me is that perhaps your temp sender or its lead wire is intermittently shorting to ground, causing the gauge to erroneously read high. Does the needle "peg" when the problem occurs?


[img=left]http://members.cox.net/clarknovak/lark.gif[/img=left]

Clark in San Diego
'63 F2/Lark Standard
http://studeblogger.blogspot.com
www.studebakersandiego.com

[rmp243]

Yes the needle pegs when this happens.

[jimmijim8]

Go to haydenauto.com to find out all about the proper operation of the fan clutch. jimmijim

Stude Junkie+++++++Do it right the f$$$$ Time. Never mind. Just do it right. When youre done your done. You'll know it.

[stall]

Hi, Try this diagnoises and troubleshooting text: I don't know for sure but vagualy remember getting it from the Corvette Forum. Cheers
---------------------------------------------------------------

On engines with belt-driven cooling fans, a fan clutch is often used to sve energy and reduce noise. The fan clutch disengages slows or disengages the engine's cooling fan when extra cooling isn't needed. The fan pulls air through the radiator and air conditioning condenser when the vehicle isn't moving fast enough to provide adequate airflow for cooling. A fan can eat up anywhere from a couple of horsepower up to 12 or 15 hp on a big V8, so by reducing the parasitic horsepower loss on the engine the fan clutch makes a noticeable difference in fuel economy.
The fan clutch also reduces noise by slowing down or disengaging the fan at high way speeds, and some even help speed engine warm up during cold weather.
TWO TYPES OF FAN CLUTCHES
There are two basic types of fan clutches: thermal and non-thermal (also called "torque limiting"). Thermal fan clutches have a temperature-sensitive bimetal coil spring on the front that reacts to temperature changes. When the air coming through the radiator is hot, the spring expands and opens an internal valve that reduces clutch slippage. This causes the fan to spin faster for increased cooling. As the air cools, the spring contracts and closes the valve. This increases the amount of clutch slippage, allowing the fan to slow down and decrease cooling.





HOW THE FAN CLUTCH WORKS
The clutch consists of a fluid coupling filled with a silicone based oil. In the cutaway view at the left, the area between the teeth on the clutch plates is filled with silicone fluid. An internal valve opens and closes a passage between the main fluid cavity and a fluid reservoir. When the passage is open, fluid enters the clutch and makes the fan to turn faster. When the valve is shut, fluid flows back to the reservoir but doesn't return, causing the clutch to slip and the fan to turn more slowly.

The non-thermal (torque limiting) fan clutch doesn't have a temperature sensing capability. It reacts only to speed, slipping to limit maximum fan speed to about 1200 to 2200 rpm depending on the application.

FAN CLUTCH PROBLEMS
A slipping fan clutch is often overlooked as the cause of an engine overheating problem.
As a fan clutch ages, fluid deterioration gradually causes an increase in slippage (about 200 rpm per year). After a number of years of service, the clutch may slip so badly that the fan can't keep up with the cooling needs of the engine and the engine overheats. At this point, replacement is often necessary.
Other signs of fan cluch failure would include any looseness in the clutch (check for fan wobble), or oil streaks radiating outward from the clutch hub.
If the clutch is binding, the fan may not release causing excessive cooling and noise, especially at highway speeds
CHECKING THE FAN CLUTCH
A good clutch should offer a certain amount of resistance when spun by hand (engine off, of course!). But if the fan spins with little resistance (more than 1 to 1-1/2 turns), the fan clutch is slipping too much and needs to be replaced.
If the fan binds, does not turn or offers a lot of resistance, it has seized and also needs to be replaced.
Fan speed can also be checked with an optical tachometer, by marking one of the fan blades with chalk and using a timing light to observe speed changes, and/or listening for changes in fan noise as engine speed changes.
You should also try to wiggle the fan blades by hand. If there is any wobble in the fan, there is a bad bearing in the fan clutch, or a worn bearing on the water pump shaft. A bad water pump bearing will usually cause the water pump to leak and/or make noise, but not always. Remove the fan clutch and see if the play is in the water pump shaft. If it feels tight (no play or wobble), replace the fan clutch.
FAN CLUTCH REPLACEMENT
Many experts say it is a good idea to replace the fan clutch at the same time as the water pump if the

[stall]

Hi Rob, I also found this very helpful site in my Computer Tech, section. Just scroll down to the fan clutch info.

http://www.aa1car.com/library/water_pump.htm

Hope this helps, Murray

http://sites.google.com/site/intrigu...tivehistories/

http://studebakerspeedster.blogspot....s-new-v-8.html

[rmp243]

Thanks for the information. I have good understanding to how this works now. I will be checking it and let everyone know what I find.

Thanks
Rob