Cooling fan issue?
01-10-2007, 09:58 PM
#1
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Join Date: Apr 2006
Location: Cincy Ohio
Posts: 358
Cooling fan issue?
Stock 88 GT. The cooling fan seems not to work right? When I start the car (40 degree's today) you can hear a clear fan sucking sound. Shoudl it be doing this when cold? The rushign wind sound dies off a little bit after driving for a but but when I shut the car off the fan spun by hand seems rather stiff still. It does move freely but is still stiff. Should it be this way?
01-10-2007, 10:08 PM
#3
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Join Date: Apr 2006
Location: Cincy Ohio
Posts: 358
RE: Cooling fan issue?
I kinda suspected that cause when hot the fan stil does not spin free to a point that you can use you finders and flick it and it spin a bit then stop, it does not do that even when hot.
01-10-2007, 10:12 PM
#5
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Join Date: Feb 2006
Location: Howard City, MI
Posts: 5,956
RE: Cooling fan issue?
The Mechanical Radiator Fan and Fan Clutch
The standard engine cooling (radiator fan) on many vehicles is of the mechanical type, meaning that it is belt-driven. In most cases the mechanical fan is mounted to the water pump snout and is driven off of the same pulley that rotates the water pump. The mechanical fan is very simple, and effective for most applications. The mechanical fans are typically made of stamped steel, but some aftermarket fans can be fiberglass, or riveted stainless blades to a stamped steel center section. Blade count varies by application, some have 4, 5, 6 or 7 blades.
Benefits of this type of fan is that it is cheap, it's simple, and it is always running. But, these can also be adverse affects. A fan that runs all the time takes power to make it work. Plus, this type of fan is not optimized at all engine speeds. Where some fans may work great a cruising speeds, they may be horrible at idle speeds (like stop and go traffic), or at higher engine speeds. Using an aftermarket fan increases airflow for better cooling, but at the expense of noise and at times even power. Some fans, like the riveted fans, can explode at certain upper RPMs and damage other engine and vehicle components.
A better street performance and at many times street/strip fan is using a mechanical fan with a fan clutch. The fan clutch is designed to drive the engine fan when air movement is needed to cool the engine. A thermostatically controlled fan clutch employs a bi-metal spring to adjust fan speed in response to operating temperature. As engine temperature rises and the radiator heats up, the air passing the radiator into the fan heats the spring coil and a silicone fluid in the clutch that enters the chamber increasing tension in the clutch and drives the fan. As coolant temperatures reduce, the fan clutch is allowed to slip, offering increased fuel efficiency and quieter operation. On the "non-thermal" fan clutch a silicone fluid with a very high shearing capability is used to drive the fan and cool the engine at lower engine speeds. As RPM increases the drive fluid allows the fan clutch to slip, increasing engine efficiency when less fan-assisted air movement is needed due to higher vehicle speeds.
Because the fan clutch and water pump share a common shaft, if the fan clutch fails it usually takes out the water pump bearing with it. To tell if a fan clutch is failing, use these common symptoms.
[ul][*]The fan clutch locks up, thereby spinning at the same RPM as the water pump. This is obvious by increased fan noise and reduced fuel efficiency. You can test this by grabbing the fan with the engine OFF and trying to turn the fan. If there is excessive resistance, or you cannot spin the fan, the fan clutch should be replaced.[*]The fan clutch will not engageand fails to turn the fan. The fan may still spin, but only as a result of centrifugal force from the already spinning pump. If you try to spin the fan with the engine OFF, the fan will spin freely with virtually no resistance. Replace the fan clutch.[*]The fan clutch explodes. This is usually caused by severe bearing failure. Fan and fan clutch parts will contact and damage the hood and other under hood engine components (belts, hoses, battery, wiring, radiator, etc.) NOTE: This is almost always due to vehicle owner "laziness" in that one of the two items above had already occurred and were ignored or not periodically inspected. [/ul]
Generally, fan clutch output under normal operating conditions will decrease by about 200 RPM per year. So, a three year old fan clutch is possibly due for replacement, or at least more periodic inspections. A four year old fan could very well be running partially disengaged and should be replaced.
With all that being cut and pasted....there sould be some resistance, but not a bad idea to replace the clutch, or upgrade to a electic fan.
The standard engine cooling (radiator fan) on many vehicles is of the mechanical type, meaning that it is belt-driven. In most cases the mechanical fan is mounted to the water pump snout and is driven off of the same pulley that rotates the water pump. The mechanical fan is very simple, and effective for most applications. The mechanical fans are typically made of stamped steel, but some aftermarket fans can be fiberglass, or riveted stainless blades to a stamped steel center section. Blade count varies by application, some have 4, 5, 6 or 7 blades.
Benefits of this type of fan is that it is cheap, it's simple, and it is always running. But, these can also be adverse affects. A fan that runs all the time takes power to make it work. Plus, this type of fan is not optimized at all engine speeds. Where some fans may work great a cruising speeds, they may be horrible at idle speeds (like stop and go traffic), or at higher engine speeds. Using an aftermarket fan increases airflow for better cooling, but at the expense of noise and at times even power. Some fans, like the riveted fans, can explode at certain upper RPMs and damage other engine and vehicle components.
A better street performance and at many times street/strip fan is using a mechanical fan with a fan clutch. The fan clutch is designed to drive the engine fan when air movement is needed to cool the engine. A thermostatically controlled fan clutch employs a bi-metal spring to adjust fan speed in response to operating temperature. As engine temperature rises and the radiator heats up, the air passing the radiator into the fan heats the spring coil and a silicone fluid in the clutch that enters the chamber increasing tension in the clutch and drives the fan. As coolant temperatures reduce, the fan clutch is allowed to slip, offering increased fuel efficiency and quieter operation. On the "non-thermal" fan clutch a silicone fluid with a very high shearing capability is used to drive the fan and cool the engine at lower engine speeds. As RPM increases the drive fluid allows the fan clutch to slip, increasing engine efficiency when less fan-assisted air movement is needed due to higher vehicle speeds.
Because the fan clutch and water pump share a common shaft, if the fan clutch fails it usually takes out the water pump bearing with it. To tell if a fan clutch is failing, use these common symptoms.
[ul][*]The fan clutch locks up, thereby spinning at the same RPM as the water pump. This is obvious by increased fan noise and reduced fuel efficiency. You can test this by grabbing the fan with the engine OFF and trying to turn the fan. If there is excessive resistance, or you cannot spin the fan, the fan clutch should be replaced.[*]The fan clutch will not engageand fails to turn the fan. The fan may still spin, but only as a result of centrifugal force from the already spinning pump. If you try to spin the fan with the engine OFF, the fan will spin freely with virtually no resistance. Replace the fan clutch.[*]The fan clutch explodes. This is usually caused by severe bearing failure. Fan and fan clutch parts will contact and damage the hood and other under hood engine components (belts, hoses, battery, wiring, radiator, etc.) NOTE: This is almost always due to vehicle owner "laziness" in that one of the two items above had already occurred and were ignored or not periodically inspected. [/ul]
Generally, fan clutch output under normal operating conditions will decrease by about 200 RPM per year. So, a three year old fan clutch is possibly due for replacement, or at least more periodic inspections. A four year old fan could very well be running partially disengaged and should be replaced.
With all that being cut and pasted....there sould be some resistance, but not a bad idea to replace the clutch, or upgrade to a electic fan.
01-10-2007, 10:31 PM
#10
2nd Gear Member
Thread Starter
Join Date: Apr 2006
Location: Cincy Ohio
Posts: 358
RE: Cooling fan issue?
Mine sounds like a jet when it takes off. Couldnt tell till my pipes were replaced and the car is quiet now. I have some play in it but not what I think it should be when warm/cold. Seems to me when the car is cold, 40 outside, the fan should spin real free, liek you push it and it spins a rotation or so.