Fan clutch
08-18-2011, 12:25 PM
#2
Le Mans Master
Park your car when it is overheating at idle, TURN THE ENGINE OFF, now try and turn the fan clutch by hand.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
Last edited by Westlotorn; 08-23-2011 at 02:48 AM. Reason: Had to add correction, "Turn the Engine OFF"
08-18-2011, 12:44 PM
#3
Drifting
Park your car when it is overheating at idle. Try and turn the fan clutch by hand.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
rustylugnuts
08-18-2011, 01:35 PM
#4
Team Owner
Member Since: Mar 2003
Location: Greenville, Indiana
Posts: 26,118
Received 1,843 Likes
on
1,398 Posts
Park your car when it is overheating at idle. Try and turn the fan clutch by hand.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
It should have significant resistance, this resistance will quickly go away as you rotate the fan since the engine is not turning. If the resistance is there the clutch is enganged.
If you rotate just a few rotations it will free spin as the silicone is pumped back into the resevoir as you rotate the fan. Engaged a fan clutch should be pulling a very large amount of air when you open the hood while idleing and overheating.
08-18-2011, 02:17 PM
#5
08-18-2011, 02:32 PM
#6
Team Owner
I don't know that there is a good way to check them unless you actually see the oil seeping out of it - when that happens it's definitely bad. That's way I replaced the clutch with a spacer...problem solved.
08-18-2011, 06:14 PM
#9
Team Owner
Member Since: Mar 2003
Location: Greenville, Indiana
Posts: 26,118
Received 1,843 Likes
on
1,398 Posts
Surely though, with some sharp lawyer on the case, he'll find a way that even this was somehow negligent on your part and you will be liable.
Some people should be arrested for getting within 50 feet of a locked toolbox!
We've come a long ways, baby!
08-19-2011, 12:29 AM
#11
Drifting
Btw , are there "stiffer" fan clutches available?
08-19-2011, 01:42 AM
#13
Drifting
08-19-2011, 02:22 AM
#14
Le Mans Master
Jokes aside all fan clutches are not equal. The OEM look alike is not heavy duty at all.
If you need to pull more air the fan clutches with an aluminum face covered with fins work better and pull more load when needed. They can turn the fan at more RPM for longer periods. As the Silicone in the clutch heats up it gets thinner, the result is less fan speed.
More fins on the front keep the clutch fluid cooler. Larger Diameter fan cluches also pull larger fan blades. All of this refer's to Thermal Fan Clutches which have a spring on the front to engage the fan when needed. If you have no spring on yours you may have found your problem. No Spring = non-Thermal fan clutch. Not nearly as effective when it is Hot outside. I have read here that the Factory Thermal Fan Clutch does work just fine on these cars even though it has no cooling fins on the front. Maybe yours is just worn out?
If you need to pull more air the fan clutches with an aluminum face covered with fins work better and pull more load when needed. They can turn the fan at more RPM for longer periods. As the Silicone in the clutch heats up it gets thinner, the result is less fan speed.
More fins on the front keep the clutch fluid cooler. Larger Diameter fan cluches also pull larger fan blades. All of this refer's to Thermal Fan Clutches which have a spring on the front to engage the fan when needed. If you have no spring on yours you may have found your problem. No Spring = non-Thermal fan clutch. Not nearly as effective when it is Hot outside. I have read here that the Factory Thermal Fan Clutch does work just fine on these cars even though it has no cooling fins on the front. Maybe yours is just worn out?
08-19-2011, 09:22 AM
#15
Burning Brakes
I recently went through this on my '67 BB. I went to the Hayden website and found the following information:
There are essentially four different types of fan clutch. The first is the one with no thermal spring and it "slips" at the same amount all the time. That's NOT what you want on a Corvette.
Then comes the Standard Duty Thermal
* Turns fan 60-70% of shaft speed when engaged.
* Disengage to 20-30% of the shaft speed
* Used with lighter pitch fans. (1-1/2” of pitch).
* Flat plate impeller design with 11.4 Sq. In. of working surface.
* Identified by a smooth steel faceplate & thermal spring assembly on the front side.
Next is the Heavy-Duty Thermal
* Turns the fan 80-90% of the shaft speed when engaged for increased cooling.
* Turns the fan 20-30% of the shaft speed when disengaged.
* Used with deeper pitch fans. (2 -1/2” of pitch).
* Land and groove design with 26.0 Sq. In. of working area allows higher operating RPM’s.
* Identified by finned aluminum faceplate and thermal spring on the front.
And finally we have the Severe Duty Thermal
* Turns the fan 80-90% of the shaft speed when engaged.
* Turns the fan 20-30% of the shaft speed when disengaged.
* Used with deeper pitch fans. (2 -1/2° of pitch).
* Land and groove design with 70 Sq. In. of working area.
* Larger working surface provides cooler running and longer life expectancy.
* Thicker body and deep finned faceplate dissipate more heat.
I found that the Hayden number 2799 was the clutch used on the '70 454 Corvette and is a Severe Duty Thermal fan and is surprisingly inexpensive. In fact, my local auto parts store had the Hayden fan for under $60.00. Another local store had a copy that was cheaper but my store of choice will price match... how can you beat that?
The Hayden website has technical data that will show you the setback, bolt dimensions and % lockup of all of their clutches. There ARE differences in the bolt pattern dimensions but luckily, the fan I have on my car is drilled for both common clutch dimensions so it fit the clutch and the clutch fit the water pump. The 2799 was SLIGHTLY taller than the clutch I had on the car so it moved the fan a little closer to the radiator which didn't seem like a bad thing.
In the end, the 2799 MOVES SOME AIR. It does cool better than the clutch I had on the car and while it doesn't LOOK exactly original (it's thicker), better cooling was what I was after.
Hope this helps,
Steve
There are essentially four different types of fan clutch. The first is the one with no thermal spring and it "slips" at the same amount all the time. That's NOT what you want on a Corvette.
Then comes the Standard Duty Thermal
* Turns fan 60-70% of shaft speed when engaged.
* Disengage to 20-30% of the shaft speed
* Used with lighter pitch fans. (1-1/2” of pitch).
* Flat plate impeller design with 11.4 Sq. In. of working surface.
* Identified by a smooth steel faceplate & thermal spring assembly on the front side.
Next is the Heavy-Duty Thermal
* Turns the fan 80-90% of the shaft speed when engaged for increased cooling.
* Turns the fan 20-30% of the shaft speed when disengaged.
* Used with deeper pitch fans. (2 -1/2” of pitch).
* Land and groove design with 26.0 Sq. In. of working area allows higher operating RPM’s.
* Identified by finned aluminum faceplate and thermal spring on the front.
And finally we have the Severe Duty Thermal
* Turns the fan 80-90% of the shaft speed when engaged.
* Turns the fan 20-30% of the shaft speed when disengaged.
* Used with deeper pitch fans. (2 -1/2° of pitch).
* Land and groove design with 70 Sq. In. of working area.
* Larger working surface provides cooler running and longer life expectancy.
* Thicker body and deep finned faceplate dissipate more heat.
I found that the Hayden number 2799 was the clutch used on the '70 454 Corvette and is a Severe Duty Thermal fan and is surprisingly inexpensive. In fact, my local auto parts store had the Hayden fan for under $60.00. Another local store had a copy that was cheaper but my store of choice will price match... how can you beat that?
The Hayden website has technical data that will show you the setback, bolt dimensions and % lockup of all of their clutches. There ARE differences in the bolt pattern dimensions but luckily, the fan I have on my car is drilled for both common clutch dimensions so it fit the clutch and the clutch fit the water pump. The 2799 was SLIGHTLY taller than the clutch I had on the car so it moved the fan a little closer to the radiator which didn't seem like a bad thing.
In the end, the 2799 MOVES SOME AIR. It does cool better than the clutch I had on the car and while it doesn't LOOK exactly original (it's thicker), better cooling was what I was after.
Hope this helps,
Steve
08-19-2011, 09:48 AM
#17
Burning Brakes
Well, based on the difference in air flow between that and my old one, it sure can't hurt!!
If your original fan won't fit the clutch, send me a PM...
Steve
If your original fan won't fit the clutch, send me a PM...
Steve
08-19-2011, 10:25 PM
#19
Safety Car
Member Since: Apr 2009
Location: Georgetown TX
Posts: 3,786
Received 573 Likes
on
307 Posts
2021 C2 of the Year Finalist - Unmodified
C2 of Year Finalist (stock) 2019
2016 C2 of Year Finalist
Did I read somewhere that the fluid in a fan clutch is silicone brake fluid?
08-20-2011, 02:46 AM
#20
Le Mans Master
It is Silicone but fluid silicone, not brake fluid. I don't know the difference. It feels like a heavy oil film to touch and does not harden when it meets air. Maybe like the stuff in implants?