Home » Public Forums » GMCnet » [GMCnet] Fan Clutch
| Re: [GMCnet] Fan Clutch [message #61280 is a reply to message #61249] |
Fri, 23 October 2009 09:28   |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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My great, great, great grandfather was;
http://en.wikipedia.org/wiki/Don_Quixote
Gordon
Ken Burton wrote:
>
> Tin Gerbil wrote on Fri, 23 October 2009 00:44
>> Ray;
>> I have a 185*F thermostat.
>>
>> You have just reiterated my point. Your old light duty fan clutch was
>> perfectly adequate for the job of cooling your engine. It was working
>> fine, until it failed. Now you have replaced it with a 4644 which is
>> not "kicking in all the time." It is kicking in at the exact same
>> temperature as the old one. The noise is generated because it is
>> coupling at it's correct ratio, of 90% of engine rpm. This is the
>> meaning of Heavy Duty. It has nothing to do with the expected life span
>> of your new fan clutch. Your old one was coupling at it's design ratio
>> of only 65% of engine rpm, therefore it made much less noise. You have
>> increased the ability of your cooling system far beyond it's needs, as
>> you state, "my engine always ran cool". Now you will burn more gas and
>> enjoy the knowledge you lacked before, that the fan was working, because
>> now you can hear it. You get to hear the extra $50 you spent on a Heavy
>> Duty Fan Clutch.
>> I stumbled upon this truth because I purchased two new 1 ton Ford diesel
>> trucks in 1987. One had the "wrong fan clutch" (according to Ford) and
>> was very quiet. One had the "correct fan clutch" and drove me nuts. I
>> replaced the noisy one with another "wrong" one and never experienced a
>> cooling problem while punishing these little trucks with 6000 pound
>> loads on very steep winding roads for many 100,000 miles. These little
>> trucks were the standard rig in a niche market of small loads of fresh
>> fish, that had to get quickly to market. My fuel mileage was so
>> consistently better than the other fellows who had identical trucks,
>> that they ignored my claims. We spent several hours per day together on
>> ferries and with nothing much to talk about, often compared our
>> operating costs. I could save my lunch money each day, in fuel cost,
>> but never let on how.
>> Gordon
>
> You are preaching to the deaf. You are not going to convert the "if it does not make a lot of noise it is not working" crowd. What you need is some numbers like how many horse power it takes to to run each of these fans.
>
> Too bad Steve did not have a more powerful and faster motor to so he could have spun his fans at normal engine cruise speed. Then he could have also measured the AC current draw on each fan. Those numbers might have gotten some of the crowd's attention.
>
> I also wish he had tested the OEM equivalent fan which is the 15-4208. That is the one he should have had for a base line to compare the others to. Unfortunately no one provided one of them for him to test.
>
> I'm not faulting Steve for what he did. I just want more and I'm too lazy to do it myself.
>
> My take on fans and clutches is they are a standby device that should only come into play in a rare circumstance when the cooling system can not handle the heat load. I suggest that that GMC cooling system should handle the heat load over 95% of the time. In the rare circumstance, like stop and go traffic with AC on in 95 degree weather, or a long hard pull up a mountain, should the fan come out of standby mode and give some additional assistance.
>
> What we are really discussing is how much additional assistance do we need. It is my contention that the OEM equivalent is sufficient and I also prefer not to hear it working.
>
> I had the 3 of the Heavy Duty Hayden's and one standard duty Hayden. I also had the AC Delco 15-4644. After talking to Danny Allen and later to an AC Delco engineer, I settled on the standard duty 15-4208 on that AC Delco recommended as equivalent to OEM. It works and it is almost silent. I also have never needed to replace a fan belt.
>
> Good luck on your crusade. I do not think the right people are listening.
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Fan Clutch [message #61281 is a reply to message #61277] |
Fri, 23 October 2009 09:43 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
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Rick;
You have rekindled my faith in the human race, after KenB had put it in
doubt.
Gordon
Rick Williams wrote:
>
> I replaced my OEM fan clutch on the road a couple of years ago. The
> only choice I had was a Hayden heavy duty. It comes on every time I
> accelerate from a stop. It is very annoying. The original rarely came
> on. I will live with it for a while yet because I hate throwing money
> away but the next one will be an AC Delco 15-4208.
>
> Rick
>
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Fan Clutch [message #61307 is a reply to message #61301] |
Fri, 23 October 2009 13:12 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Can you find a picture of it Larry....that will tell the story if it's the HD or OEM size.
Ray
Ray & Lisa Erspamer
78 Royale Center Kitchen
The Malosco Cruiser (TZE368V101144)
Wauwatosa, Wisconsin 53226
Email: 78GMC-Royale@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/
________________________________
From: Larry <weidnerl@wwt.net>
To: gmclist@temp.gmcnet.org
Sent: Friday, October 23, 2009 12:36:11 PM
Subject: Re: [GMCnet] Fan Clutch
FYI, did a search for 15- 4208 at ACdelco.com and got this:
CLUTCH,FAN BLADE
Part Number: 15-4947
Requested part 15-4208 has been superseded.
HUmmm...wonder which one this really is...light, normal or heavy duty?
--
Larry :)
78 Royale w/500 Caddy
Menomonie, WI.
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: [GMCnet] Fan Clutch [message #61308 is a reply to message #61301] |
Fri, 23 October 2009 13:16 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
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Severe duty fan clutch (Hayden #2797, #2749, and AC Delco 15-4208
Found in "Junk Yard Gems"
http://www.gmcws.org/Tech/junkyardgems/index.htm
Part Number: 15-4947 referred to as Heavy duty by some and Severe duty
by others. I did not find the coupling % specs. It is the correct fan
for those who wish to pretend they are flying a B-25, while motoring
along in their GMC's. I am beginning to wonder if the HD fan's main use
is to drown out co-pilots? (:>
Gordon
Larry wrote:
>
> FYI, did a search for 15- 4208 at ACdelco.com and got this:
>
> CLUTCH,FAN BLADE
> Part Number: 15-4947
> Requested part 15-4208 has been superseded.
>
> HUmmm...wonder which one this really is...light, normal or heavy duty?
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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| Re: [GMCnet] Fan Clutch [message #61314 is a reply to message #61301] |
Fri, 23 October 2009 13:43 |
Ray Erspamer
Messages: 1707
Registered: May 2007
Location: Milwaukee Wisconsin
Karma: -3
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Napa shows the exact same picture and part number (271305) for both the 15-4208 and 15-4947, definitely the smaller (thinner) model than the 15-4644 heavy duty.
Ray & Lisa Erspamer
78 Royale Center Kitchen
The Malosco Cruiser (TZE368V101144)
Wauwatosa, Wisconsin 53226
Email: 78GMC-Royale@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/
________________________________
From: Larry <weidnerl@wwt.net>
To: gmclist@temp.gmcnet.org
Sent: Friday, October 23, 2009 12:36:11 PM
Subject: Re: [GMCnet] Fan Clutch
FYI, did a search for 15- 4208 at ACdelco.com and got this:
CLUTCH,FAN BLADE
Part Number: 15-4947
Requested part 15-4208 has been superseded.
HUmmm...wonder which one this really is...light, normal or heavy duty?
--
Larry :)
78 Royale w/500 Caddy
Menomonie, WI.
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Ray Erspamer
78 GMC Royale Center Kitchen
403, 3.70 Final Drive
Holley Sniper Quadrajet EFI System,
Holley Hyperspark Ignition System
414-484-9431
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| Re: [GMCnet] Fan Clutch [message #61326 is a reply to message #61249] |
Fri, 23 October 2009 14:50 |
Rick Denney
Messages: 430
Registered: January 2004
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Ken Burton writes...
> My take on fans and clutches is they are a standby device that
> should only come into play in a rare circumstance when the cooling
> system can not handle the heat load.
How do you square that with what I've been reporting of my detailed
observations, that the temperature rises while driving on a hilly
interstate unless the clutch engages to drop it back down? Seems to me
that ram air ought to maintain the radiator at the thermostat with no
fan at all. But it doesn't. And you know my cooling sysem is tip-top.
I'm not arguing that the 4208 isn't adequate, but I am arguing that
the clutch is more than a standby device. With the 4208, I could never
really tell what was going on.
Rick "deaf, I suppose... sheesh" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Fan Clutch [message #61371 is a reply to message #61326] |
Fri, 23 October 2009 18:31 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Rick,
So if I read what you note below correctly you couldn't hear the fan when it
kicked in and out but the engine temps were OK?
Was this with a standard radiator or an aluminum one?
Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rick Denney
Sent: Saturday, 24 October 2009 6:50 AM
To: Ken Burton
Subject: Re: [GMCnet] Fan Clutch
I'm not arguing that the 4208 isn't adequate, but I am arguing that
the clutch is more than a standby device. With the 4208, I could never
really tell what was going on.
Rick "deaf, I suppose... sheesh" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Fan Clutch [message #61398 is a reply to message #61326] |
Fri, 23 October 2009 21:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Rick Denney wrote on Fri, 23 October 2009 14:50 |
Ken Burton writes...
> My take on fans and clutches is they are a standby device that
> should only come into play in a rare circumstance when the cooling
> system can not handle the heat load.
How do you square that with what I've been reporting of my detailed
observations, that the temperature rises while driving on a hilly
interstate unless the clutch engages to drop it back down? Seems to me
that ram air ought to maintain the radiator at the thermostat with no
fan at all. But it doesn't. And you know my cooling sysem is tip-top.
I'm not arguing that the 4208 isn't adequate, but I am arguing that
the clutch is more than a standby device. With the 4208, I could never
really tell what was going on.
Rick "deaf, I suppose... sheesh" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
|
It squares with me. I never see the temp gauge move once it has warmed up. You gauge is probably more sensitive than mine. I also seldom hear my fan kick in. Granted I have very poor hearing. I can hear it in the morning when I first start out up to 15 or 20 mph.
If you have cooling problems with that aluminum radiator on a 23 foot coach, I would be looking for the over heat or lack of cooling problem. Things like weak pump, air flow restrictions, or timing issues come to mind. Putting on a larger capacity fan just masks the real issue.
JMHO
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Fan Clutch [message #61407 is a reply to message #61398] |
Fri, 23 October 2009 22:56 |
 |
WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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For years I have read these threads on fan clutches and kept silent, believe it or not. Did not want to tell anyone about how my engines stays cool. No one would believe me. But, hey, why not? Back in 07 we replaced a perfectly good radiator with a new aluminum one. Why? Well, I knew I was going to be spending time out west during the hot summer months and I wanted no surprise problems. I have a temperature gauge and I also have a Digipanel that reads the engine temp. Teri and I crossed the state of Az. in 112 degree temperature, late June. We climbed the grade, on I-40, west out of Needles. The two temperature gauges never went above 210 and that was on the grade out of Needles. The rest of the time the temperature sat at 195, which is the thermostat rating that I have. We climbed over from I-5 to Gilroy in 100 degree heat, towing the Vibe. Tranny heated up, had a 307 then, but the engine never went over 200 there and it was 100 degrees. Bottom line, I have never heard my fan clutch come on and I hope I never do. Is it working? I have no clue, but I know that I have no over heating issues. I feel like a very lucky soul in the area of non over heating. I hope I have not jinxed myself. By the way, my tranny has never over heated again since we installed the 355.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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| Re: [GMCnet] Fan Clutch [message #61414 is a reply to message #61371] |
Sat, 24 October 2009 01:35 |
Rick Denney
Messages: 430
Registered: January 2004
Karma: 0
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Rob Mueller writes...
> Rick,
> So if I read what you note below correctly you couldn't hear the fan when it
> kicked in and out but the engine temps were OK?
I never heard the fan engage with the 4208. The engine temps wandered
around quite a bit, though it never overheated by any means. I could
never tell if or when the fan was engaged, so I have no idea how it
affected coolant temperatures. When the 4644 engages, I hear it but
the coolant temperature (as measured at the engine) would beging to
drop within seconds and would drop 10-15 degrees in less than 30
seconds. That may be overkill and it may be that the 4208 was doing
its job.
Part of my motivation was not just to cool the coolant, however. I was
also hoping to more positively flush hot air out of the engine
compartment when the engine was making a lot of heat. I have had fuel
overheat problems, and I'm seeing if that has an effect. It will take
a couple of years of usage to have a sense of that.
My measurements early on after installing the aluminum radiator (and
then the manifold) were confused by a temp gauge that went faulty on
me at some point, and by the temporary use of a Flowkooler-modified
thermostat (too much bypass) and a Stant (too little flow).
> Was this with a standard radiator or an aluminum one?
Aluminum. My old radiator has a repair plug in the core the size of a
baseball. I never knew what that was doing, either.
Rick "not ruling out going back to the 4208 at some point, now that
the behavio in practice is clearer" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Fan Clutch [message #61417 is a reply to message #61398] |
Sat, 24 October 2009 02:38 |
Rick Denney
Messages: 430
Registered: January 2004
Karma: 0
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Ken Burton writes...
> It squares with me. I never see the temp gauge move once it has
> warmed up. You gauge is probably more sensitive than mine. I also
> seldom hear my fan kick in. Granted I have very poor hearing. I
> can hear it in the morning when I first start out up to 15 or 20 mph.
I never could hear the 4208 even in the morning. Even with the engine
hatch open. And I'm not dang-near deaf like you are.
Yes, my gauge is a mechanical Autometer temp gauge with a 270-degree
dial, so I can read down to the degree with precision and (I assume)
accuracy. And I would expect its response time to temperatur changes
to be measured in the single digits of seconds, with little or no
damping beyond that.
> If you have cooling problems with that aluminum radiator on a 23
> foot coach, I would be looking for the over heat or lack of cooling
> problem. Things like weak pump, air flow restrictions, or timing
> issues come to mind. Putting on a larger capacity fan just masks the real issue.
You live in flat land. The engine heats up when I climb hills at 55-65
mph. (My "hills" often have 6%, and occasionally 8%, grades.) It cools
down on the other side. There is nothing wrong with my cooling
system--new everything, right down to the recovery tank.
And if there are air-flow restrictions, they were put there by GMC.
But the results of my testing, in my mind, PROVE that there are
air-flow restrictions, and NOT cooling system problems. Engine warms
up under ram air. Fan kicks in. Engine IMMEDIATELY cools 10-15 degrees
with 20-30 seconds. Fan clutch disengages. By that time, I'm to the
next hill and the process repeats. Running the dash air, which dumps
heat in front of the radiator, increases this cycling.
If the fan can reduce coolant temperature that much in under half a
minute, then there's nothing wrong with the cooling system. If the
cooling system was inadequate, the fan wouldn't help that effectively.
But a fan should not normally be able to increase the air flow
usefully when driving at 65mph. We know that it does, because of the
effect it has on coolant temps. The only possible conclusion I can
think of is that a pressure bubble forms in the engine compartment,
preventing unaided air flow from flushing the compartment out. And the
fan, with enough power behind it, forces that pressure bubble to be
flushed out by creating a still higher pressure.
We have always contended that a cooling problem should be addressed
first, and I've done that. And I've instrumented the engine temp well
enough to know what effect the fan has on it. I think I've shown
pretty conclusively that even a top-notch cooling system will show
temperature cycling that is controlled with a positive and power fan
drive. I may have shown why it is that Gene hasn't been able to come
up with an electric-fan arrangement that works--the system depends too
much on the fan.
I think all this is masked by the stock temperature gauge, which seems
to be too well-damped to show these interactions.
Rick "speaking of masking..." Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Fan Clutch [message #61419 is a reply to message #61407] |
Sat, 24 October 2009 02:44 |
Rick Denney
Messages: 430
Registered: January 2004
Karma: 0
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Senior Member |
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Dan Gregg writes...
> Bottom line, I have never heard my fan clutch come on and I hope I
> never do. Is it working? I have no clue...
Based on my experience, if your clutch wasn't working, you would not
have gotten the results you did. So, your clutch is doing
somemthing--you just don't know what. That's one reason I installed a
4644--I wanted to KNOW what it was doing. Without that, my experience
would have been roughly similar to yours--including the not knowing.
Rick "noting that mechanical fan clutches don't have indicator lights"
Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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| Re: [GMCnet] Fan Clutch [message #61420 is a reply to message #61414] |
Sat, 24 October 2009 02:47 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Rick,
Thanks for the explanation!
With all the information regarding this subject I have a good handle on the
cooling system which I will put to use when I get back to the USA next
summer and get Double Trouble ready for the yearly tour.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rick Denney
Sent: Saturday, 24 October 2009 5:35 PM
To: Rob Mueller
Subject: Re: [GMCnet] Fan Clutch
Rob Mueller writes...
> Rick,
> So if I read what you note below correctly you couldn't hear the fan when
it
> kicked in and out but the engine temps were OK?
I never heard the fan engage with the 4208. The engine temps wandered
around quite a bit, though it never overheated by any means. I could
never tell if or when the fan was engaged, so I have no idea how it
affected coolant temperatures. When the 4644 engages, I hear it but
the coolant temperature (as measured at the engine) would beging to
drop within seconds and would drop 10-15 degrees in less than 30
seconds. That may be overkill and it may be that the 4208 was doing
its job.
Part of my motivation was not just to cool the coolant, however. I was
also hoping to more positively flush hot air out of the engine
compartment when the engine was making a lot of heat. I have had fuel
overheat problems, and I'm seeing if that has an effect. It will take
a couple of years of usage to have a sense of that.
My measurements early on after installing the aluminum radiator (and
then the manifold) were confused by a temp gauge that went faulty on
me at some point, and by the temporary use of a Flowkooler-modified
thermostat (too much bypass) and a Stant (too little flow).
> Was this with a standard radiator or an aluminum one?
Aluminum. My old radiator has a repair plug in the core the size of a
baseball. I never knew what that was doing, either.
Rick "not ruling out going back to the 4208 at some point, now that
the behavio in practice is clearer" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Fan Clutch [message #61431 is a reply to message #61417] |
Sat, 24 October 2009 09:09 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Rick Denney wrote on Sat, 24 October 2009 02:38 |
Ken Burton writes...
> It squares with me. I never see the temp gauge move once it has
> warmed up. You gauge is probably more sensitive than mine. I also
> seldom hear my fan kick in. Granted I have very poor hearing. I
> can hear it in the morning when I first start out up to 15 or 20 mph.
I never could hear the 4208 even in the morning. Even with the engine
hatch open. And I'm not dang-near deaf like you are.
Yes, my gauge is a mechanical Autometer temp gauge with a 270-degree
dial, so I can read down to the degree with precision and (I assume)
accuracy. And I would expect its response time to temperatur changes
to be measured in the single digits of seconds, with little or no
damping beyond that.
> If you have cooling problems with that aluminum radiator on a 23
> foot coach, I would be looking for the over heat or lack of cooling
> problem. Things like weak pump, air flow restrictions, or timing
> issues come to mind. Putting on a larger capacity fan just masks the real issue.
You live in flat land. The engine heats up when I climb hills at 55-65
mph. (My "hills" often have 6%, and occasionally 8%, grades.) It cools
down on the other side. There is nothing wrong with my cooling
system--new everything, right down to the recovery tank.
And if there are air-flow restrictions, they were put there by GMC.
But the results of my testing, in my mind, PROVE that there are
air-flow restrictions, and NOT cooling system problems. Engine warms
up under ram air. Fan kicks in. Engine IMMEDIATELY cools 10-15 degrees
with 20-30 seconds. Fan clutch disengages. By that time, I'm to the
next hill and the process repeats. Running the dash air, which dumps
heat in front of the radiator, increases this cycling.
If the fan can reduce coolant temperature that much in under half a
minute, then there's nothing wrong with the cooling system. If the
cooling system was inadequate, the fan wouldn't help that effectively.
But a fan should not normally be able to increase the air flow
usefully when driving at 65mph. We know that it does, because of the
effect it has on coolant temps. The only possible conclusion I can
think of is that a pressure bubble forms in the engine compartment,
preventing unaided air flow from flushing the compartment out. And the
fan, with enough power behind it, forces that pressure bubble to be
flushed out by creating a still higher pressure.
We have always contended that a cooling problem should be addressed
first, and I've done that. And I've instrumented the engine temp well
enough to know what effect the fan has on it. I think I've shown
pretty conclusively that even a top-notch cooling system will show
temperature cycling that is controlled with a positive and power fan
drive. I may have shown why it is that Gene hasn't been able to come
up with an electric-fan arrangement that works--the system depends too
much on the fan.
I think all this is masked by the stock temperature gauge, which seems
to be too well-damped to show these interactions.
Rick "speaking of masking..." Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
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You may be onto something there. I never reinstalled my fender liners after my fire so my airflow is probably greatly different than yours.
I do live in flatland country but I travel to other places like the Pueblo rally at 5000 feet. After the rally I was as high as 9000 feet. I have been up to 11,000 at the Eisenhower tunnel and Trail Ridge road. I do not pay much attention to the % of grade as much as I do the the altitude. The altitude affects my engine performance and how long it is going to take me to get to the top.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Fan Clutch [message #61436 is a reply to message #61414] |
Sat, 24 October 2009 09:37 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Oct 24, 2009, at 12:35 AM, Rick Denney <rick@rickdenney.com> wrote:
> Rob Mueller writes...
>
>> Rick,
>
>> So if I read what you note below correctly you couldn't hear the
>> fan when it
>> kicked in and out but the engine temps were OK?
>
> I never heard the fan engage with the 4208. The engine temps wandered
> around quite a bit, though it never overheated by any means. I could
> never tell if or when the fan was engaged, so I have no idea how it
> affected coolant temperatures. When the 4644 engages, I hear it but
> the coolant temperature (as measured at the engine) would beging to
> drop within seconds and would drop 10-15 degrees in less than 30
> seconds.
That is exactly the reason that I have been using my AC/Delco 15-4644
for about 8 years now.
Someone on the net has been repeatedly telling us, to ad nauseum, that
we are wasting horsepower by using the "heavy duty" clutch but I think
he is totally overlooking the fact that if you, for example, use two
hp for 30 seconds that is the same as using 1 hp for 60 seconds.
When my temperature starts to climb when pulling my toad up a steep
grade I want to cool things down quickly. I find that if my
temperature hits about 205 the clutch kicks in and within a few
seconds it cools back to 195 and turns off.
As you point out, this happens in about 30 seconds. When on level
ground the clutch never comes on.
Emery Stora
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| Re: [GMCnet] Fan Clutch [message #61437 is a reply to message #61301] |
Sat, 24 October 2009 09:45 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Larry wrote on Fri, 23 October 2009 12:36 |
FYI, did a search for 15- 4208 at ACdelco.com and got this:
CLUTCH,FAN BLADE
Part Number: 15-4947
Requested part 15-4208 has been superseded.
HUmmm...wonder which one this really is...light, normal or heavy duty?
|
I have no knowledge on the 15-4947.
The work I did on these clutches with AC Delco engineering was several years ago and the recommendation at the time was 15-4208. The engineer I worked with had me get the fan diameter and fan pitch for him. Denny Allen had one out so I got the measurements from him. With that data he recommended the 15-4208.
He was able to find the specs on the original GM part number we used and said the specs on the 15-4208 were about the same.
At the time I asked about the 15-4644. He said it was for a minimum 2" larger diameter fan with at least one more inch in the pitch. He also stated that it needed at least two 1/2" wide belts to drive it. When I told him some GMCers were using the 15-4644 with two 7/16" belts, he asked me how their fan belt, alternator, and water pump bearing life was. I told him I did not know.
He said the 15-4208 needs a minimum of two 3/8" belts to drive it. He saw no problem when I told him ours were really two, or three with the optional AC installed, 7/16" belts.
The most recent one I bought was in July and I forwarded that one to Canada so I never even opened the box.
All I can say is someone needs to buy one of the new ones and try it. I also see the new part number is $66.00 where the 15-4208 was $50.00
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Fan Clutch [message #61445 is a reply to message #61437] |
Sat, 24 October 2009 11:24 |
Tin Gerbil
Messages: 236
Registered: October 2006
Location: Vancouver Island, B.C.
Karma: 0
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Senior Member |
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Ken;
The rule of thumb we were given when building belt driven equipment was
a one half wrap on a 6" pulley, using a 3/8" belt will transmit a
maximum of 5 hp before it slips excessively. IIRC the reason for
switching to a viscous coupled fan was because under normal driving
conditions a car fan uses up to 17 hp. Yes, I realize these two
statements do not match. As your engineer said you needed two 3/8"
belts, I will assume 10hp. What no one has addressed, is the fact that
the fan and shroud in a GMC are reducing the air flow through the
radiator when the fan clutch is not engaged. Ken has pointed out that
the nature of air is that it will go everywhere but where you need it.
When the automotive industry switched from engine driven fans to
electric, at first they used shrouds. Most vehicles have now done away
with shrouds on electric fans. They did this to improve air flow
through the radiator under normal driving conditions. They cool better
without a shroud. Depending on the design of the radiator, it takes
approximately 5 mph to get air moving through the radiator. We know
this from Honda who have the electric fans blowing forward, out, through
the radiator on all of their large motorcycles. At 5 mph, they shut off
the fan and depend on ram air. If you putt along at 5 mph, as in a
parade, you quickly boil over. The fan never comes on over this speed.
What one of the brilliant mathematicians (who appears to know a lot of
chemistry) in the crowd does not seem to be able to calculate is the
FACT that a Heavy Duty Fan Clutch contains viscous fan clutch fluid of
10,000 CTS. A Light Duty Fan Clutch is using 3,000 CTS fluid. The
heavier fluid drags the fan, around using more horsepower at all times,
not just during maximum couple. This is why I was able to document
better fuel mileage with my diesel trucks when using Light Duty Fan
Clutches. 10% coupling 99% of the time vs 33% coupling 99% of the time.
1 hp 99% of the time vs 3.3 hp 99% of the time. A simple way to
observe this is to paint one fan blade, start a cold engine and let it
idle for one minute. Shut it off and count the number of revolutions
before a light duty clutch stops. Put on a Heavy duty clutch and do the
same test. I really should have taken KenB's advice, as most people
just won't get it.
One other point on fan clutches that so many have experienced failures
with. You can carry a simple locking plate made of 1/8" aluminum. It
has a "U" shaped cutout that slips into the wrench slot on the shaft.
You use two of the fan clutch mounting bolts to lock the shaft to the
clutch. This should have great appeal to those who like to know the fan
is working, as it will now be roaring all the way home and they will be
in true, severe, 100%, heavy duty fan clutch heaven.
Most fan clutches can be repaired by people with very little skill at
minimal cost. If you can get it off the engine, you can repair it. But
then Y'all probably want to switch to a Severe Heavy Duty Clutch anyway.
Send me a PM if you want the rebuild instructions.
Gordon "ad nauseum"
Ken Burton wrote:
>
> Larry wrote on Fri, 23 October 2009 12:36
>> FYI, did a search for 15- 4208 at ACdelco.com and got this:
>>
>> CLUTCH,FAN BLADE
>> Part Number: 15-4947
>> Requested part 15-4208 has been superseded.
>>
>> HUmmm...wonder which one this really is...light, normal or heavy duty?
>
>
>
> I have no knowledge on the 15-4947.
>
> The work I did on these clutches with AC Delco engineering was several years ago and the recommendation at the time was 15-4208. The engineer I worked with had me get the fan diameter and fan pitch for him. Denny Allen had one out so I got the measurements from him. With that data he recommended the 15-4208.
>
> He was able to find the specs on the original GM part number we used and said the specs on the 15-4208 were about the same.
>
> At the time I asked about the 15-4644. He said it was for a minimum 2" larger diameter fan with at least one more inch in the pitch. He also stated that it needed at least two 1/2" wide belts to drive it. When I told him some GMCers were using the 15-4644 with two 7/16" belts, he asked me how their fan belt, alternator, and water pump bearing life was. I told him I did not know.
>
> He said the 15-4208 needs a minimum of two 3/8" belts to drive it. He saw no problem when I told him ours were really two, or three with the optional AC installed, 7/16" belts.
>
> The most recent one I bought was in July and I forwarded that one to Canada so I never even opened the box.
>
> All I can say is someone needs to buy one of the new ones and try it. I also see the new part number is $66.00 where the 15-4208 was $50.00
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Gordon
'74 Canyon Lands "Tin Gerbil"
Vancouver Island, B.C.
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