Home » Public Forums » GMCnet » Re: [GMCnet] Another fan clutch story
| Re: [GMCnet] Another fan clutch story [message #95552] |
Thu, 12 August 2010 14:01  |
Gary Casey
Messages: 448
Registered: September 2009
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That would be my first choice. Although adding complete bulkhead even with the
radiator all the way across would be a challenge I think it would do the most
good. While deflectors of various configurations would help, there is still a
lot of room for air to go around the radiator instead of through it.
Gary Casey
Previously:
If lower air pressure behind the radiator is what is needed,,,could we block the
air off completly on the sides???? Its a pretty large space on the sides. And I
don't mean the side "thingies" on my 78. Completely block the air outboard of
those. Would need to provide cooling for the PS pump.,,,PL
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| Re: [GMCnet] Another fan clutch story [message #95592 is a reply to message #95563] |
Thu, 12 August 2010 19:13  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| g.winger wrote on Thu, 12 August 2010 13:46 |
Wish I had some type of sesitive air pressure gauge,,,hmmmm
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Ever heard of a home-made Manometer?
Here is one:
<http://www.komar.org/faq/manometer/>
A little bulky but cheap and accurate for relative measurements.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Another fan clutch story [message #95642 is a reply to message #95563] |
Fri, 13 August 2010 01:31 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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| g.winger wrote on Thu, 12 August 2010 15:46 |
Wish I had some type of sesitive air pressure gauge,,,hmmmm
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I sent Rick Denney one to try a few months back. I do not know if he ever tried it out.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Another fan clutch story [message #95664 is a reply to message #95642] |
Fri, 13 August 2010 09:03 |
Richard Denney
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Registered: April 2010
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On Fri, Aug 13, 2010 at 2:31 AM, Ken Burton <n9cv@comcast.net> wrote:
> I sent Rick Denney one to try a few months back. I do not know if he ever
> tried it out.
>
>
Yes, you did, and no, I didn't. I've been so hammered with everything right
now that the only experimentation I can do on this topic is with words.
If someone else is ready to make use of it, or if you want it back, tell me
where to send it and I'll do so.
For others: It is an airspeed indicator, which is really just a variable
pressure gauge that compares the dynamic pressure being pushed into a pitot
tube (which is pointed into the wind) with the slight vacuum caused by air
flowing past a port on the side of an airplane. It is sensitive and can act
as in place of a manometer. But a water manometer is probably easier to
construct.
My idea was to measure pressure at various points in the engine compartment
while driving at highway speed. The points I wanted to measure are in front
of the AC condenser, behind the radiator (inside the shroud, with and
without the fan engaged), behind the fan (with and without engagement), and
in the space next to the back side of the shroud. I suspect that space has
less pressure than on top of the engine. My theory is that the idled fan
might be blocking air flow enough to create a pressure bubble within the
shroud, and providing flapper vents on the shroud might relieve this
pressure enough to significantly increase air flow through the radiator.
Adding duct work would make that work even better.
On the subject of ductwork, an enclosed duct from the radiator frame to the
grille would be easier than a solid bulkhead on the radiator plane, it seems
to me. It would have fewer penetrations to have to seal up, and it could be
done easily with flexible materials. Given my battery location, vacuum pump
location, and stuff like that, I would rather not have to deal with the
interference those would cause.
A solid duct from the grille to the radiator would still, however, be open
at the bottom, and I'm not sure the grille by itself is big enough to
provide the air flow we need. Putting a duct around that bottom area to
provide a grilled under the bumper would really decrease front ground
clearance, which is a killer for me. This recommends more in favor of the
bulkhead. But I'll try what's easiest first.
Providing more pressure going in will help less than it could, though, if we
block pressure going out. That's why I keep coming back to those flapper
vents.
And, Steve, I just can't make this a clutch issue. Maybe a different clutch
would make it less noisy, but the fact remains that when the clutch is NOT
engaged, my coolant temperature climbs when it should not. My cooling system
is about as good as it gets with an aluminum radiator, a proper mix of
coolant, a fresh water pump, and a proper RobertShaw 180-degree thermostat.
Seems to me that if the needle is moving up on steady highway cruise, ANY
clutch will eventually have to engage to control it. I'm happy with that
engagement when it's particularly hot, when I'm making lots of power, or
when I'm going slowly--that's what it's there for. But I would rather the
cooling system keep the temperature down on the stat when cruising on a
normal Interstate on a moderate day.
Rick "really going to try to work on that ducting issue" Denney
--
'73 230 "Jaws"
Northern Virginia
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| Re: [GMCnet] Another fan clutch story [message #95667 is a reply to message #95664] |
Fri, 13 August 2010 09:22 |
emerystora
Messages: 4442
Registered: January 2004
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On Aug 13, 2010, at 8:03 AM, Richard Denney <rwdenney@gmail.com> wrote:
>
> And, Steve, I just can't make this a clutch issue. Maybe a different
> clutch
> would make it less noisy, but the fact remains that when the clutch
> is NOT
> engaged, my coolant temperature climbs when it should not. My
> cooling system
> is about as good as it gets with an aluminum radiator, a proper mix of
> coolant, a fresh water pump, and a proper RobertShaw 180-degree
> thermostat.
>
One thing you might want to do to see if if would help level out your
temperatures is to try a 195 deg. thermostat.
Let us know if this changes things.
Emery Stora
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| Re: [GMCnet] Another fan clutch story [message #95670 is a reply to message #95664] |
Fri, 13 August 2010 10:17 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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""Seems to me that if the needle is moving up on steady highway cruise, ANY
clutch will eventually have to engage to control it. I'm happy with that
engagement when it's particularly hot, when I'm making lots of power, or
when I'm going slowly--that's what it's there for. But I would rather the
cooling system keep the temperature down on the stat when cruising on a
normal Interstate on a moderate day.
Rick "really going to try to work on that ducting issue" Denney
""
Rick--I'm sure there are improvements to be made via ducting as well as lower spoilers, however the condition you are describing just doesn't sound normal for a stock set up esp with an aluminum radiator. Even though this has been a heated discussion on fan clutches (pun intended) what you are describing is not a clutch issue--as you mention. Given all that, I would find out why your temperature is climbing on level cruise before you resort to making changes. Many of us can drive on the level with stock radiators in over 100F and not have the clutch come on. I think you have something else going on there.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Another fan clutch story [message #95677 is a reply to message #95667] |
Fri, 13 August 2010 10:57 |
Richard Denney
Messages: 920
Registered: April 2010
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One thing you might want to do to see if if would help level out your
> temperatures is to try a 195 deg. thermostat.
>
> Let us know if this changes things.
>
>
I dunno, Emery. My clutch seems to engage when the temperature inches its
way up into the 190-degree range. If the temperature rises quickly, say
because of a steep climb, the temperature might rise higher than that before
the temperature at the clutch catches up to it. But I have this feeling that
a 195-degree thermostat, under my current conditions, would mean that the
clutch stayed engaged more often, because the coolant temperature would not
inch its way up to 190, it would rise to the stat level much more quickly.
Perhaps Bob is right that there is some other thing going on. But I'll be
doggoned if I can figure out what it is. If there was a flaw in the cooling
system, then why would the coolant temperature drop so quickly when the fan
does engage? So, if the climbing coolant temps are a result of something
wrong, then it has to be something causing excessive heat production. It
seems to me that heat PRODUCTION is a result of power production and little
else. Heat REDUCTION is a function of the cooling system.
Rick "who has already checked the ignition timing and looked without finding
evidence of over-lean mixtures" Denney
--
'73 230 "Jaws"
Northern Virginia
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| Re: [GMCnet] Another fan clutch story [message #95682 is a reply to message #95677] |
Fri, 13 August 2010 11:42 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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"" It
seems to me that heat PRODUCTION is a result of power production and little
else. Heat REDUCTION is a function of the cooling system.
""
Well there's another factor in there and it's an issue of efficiency on both sides. We all know that retarded timing can cause an engine to run hot for a certain amount of power output because of poor efficiency. Also--there is the AC condenser, transmission intercooler and an engine oil intercooler in the system that will ask for heat transfer. We have heard of people who have had a transmission running excessively hot for various reasons. Since you put in a new radiator, I doubt that you have crap between it and the condensor.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Another fan clutch story [message #95687 is a reply to message #95682] |
Fri, 13 August 2010 12:15 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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This whole discussion triggered a thought. This whole scenario is
interrelated. Fan, Fan clutch, shroud, a/c condensor, oil and transmission
coolers, thermostat, pressure cap, coolant mix etc. There are so many
variables that it is hard to consider all the possible cause and effects.
Sorta like the old adage, "When you are up to your butt in alligators, it is
hard to remember that the original objective was to drain the swamp."
Obviously, the best radiator in the world can't do it's job if you can't
move air through it and when the fan clutch cycles on in every case the temp
comes down. Seems like improved airflow is the short term answer. Just what
I think.
Jim Hupy
Salem, Or
78 Royale 403
On Fri, Aug 13, 2010 at 9:42 AM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
>
> "" It
> seems to me that heat PRODUCTION is a result of power production and little
> else. Heat REDUCTION is a function of the cooling system.
> ""
>
> Well there's another factor in there and it's an issue of efficiency on
> both sides. We all know that retarded timing can cause an engine to run hot
> for a certain amount of power output because of poor efficiency. Also--there
> is the AC condenser, transmission intercooler and an engine oil intercooler
> in the system that will ask for heat transfer. We have heard of people who
> have had a transmission running excessively hot for various reasons. Since
> you put in a new radiator, I doubt that you have crap between it and the
> condensor.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
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| Re: [GMCnet] Another fan clutch story [message #95691 is a reply to message #95670] |
Fri, 13 August 2010 12:58 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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| Bob de Kruyff wrote on Fri, 13 August 2010 10:17 |
""Seems to me that if the needle is moving up on steady highway cruise, ANY
clutch will eventually have to engage to control it. I'm happy with that
engagement when it's particularly hot, when I'm making lots of power, or
when I'm going slowly--that's what it's there for. But I would rather the
cooling system keep the temperature down on the stat when cruising on a
normal Interstate on a moderate day.
Rick "really going to try to work on that ducting issue" Denney
""
Rick--I'm sure there are improvements to be made via ducting as well as lower spoilers, however the condition you are describing just doesn't sound normal for a stock set up esp with an aluminum radiator. Even though this has been a heated discussion on fan clutches (pun intended) what you are describing is not a clutch issue--as you mention. Given all that, I would find out why your temperature is climbing on level cruise before you resort to making changes. Many of us can drive on the level with stock radiators in over 100F and not have the clutch come on. I think you have something else going on there.
|
It sounds like retarded timing at cruising speeds to me.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Another fan clutch story [message #95692 is a reply to message #95677] |
Fri, 13 August 2010 13:02 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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| Richard Denney wrote on Fri, 13 August 2010 10:57 |
One thing you might want to do to see if if would help level out your
I dunno, Emery. My clutch seems to engage when the temperature inches its
way up into the 190-degree range. If the temperature rises quickly, say
because of a steep climb, the temperature might rise higher than that before
the temperature at the clutch catches up to it. But I have this feeling that
a 195-degree thermostat, under my current conditions, would mean that the
clutch stayed engaged more often, because the coolant temperature would not
inch its way up to 190, it would rise to the stat level much more quickly.
Perhaps Bob is right that there is some other thing going on. But I'll be
doggoned if I can figure out what it is. If there was a flaw in the cooling
system, then why would the coolant temperature drop so quickly when the fan
does engage? So, if the climbing coolant temps are a result of something
wrong, then it has to be something causing excessive heat production. It
seems to me that heat PRODUCTION is a result of power production and little
else. Heat REDUCTION is a function of the cooling system.
Rick "who has already checked the ignition timing and looked without finding
evidence of over-lean mixtures" Denney
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Has anyone tried taking the front grill off to see if that changes things? More air flow, more pressure against the radiator without the grill restriction? Just wondering...
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: [GMCnet] Another fan clutch story [message #95693 is a reply to message #95687] |
Fri, 13 August 2010 13:10 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""This whole discussion triggered a thought. This whole scenario is
interrelated. Fan, Fan clutch, shroud, a/c condensor, oil and transmission
coolers, thermostat, pressure cap, coolant mix etc. There are so many
variables that it is hard to consider all the possible cause and effects.
Sorta like the old adage, "When you are up to your butt in alligators, it is
hard to remember that the original objective was to drain the swamp."
Obviously, the best radiator in the world can't do it's job if you can't
move air through it and when the fan clutch cycles on in every case the temp
comes down. Seems like improved airflow is the short term answer. Just what
I think.
Jim Hupy
Salem, Or
78 Royale 403
"" That's for sure--it's all a big system and maybe that's why so many of us are seeing various results because the state of our individual parts of the system are different. This continues to be one heck of a discussion.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Another fan clutch story [message #95694 is a reply to message #95692] |
Fri, 13 August 2010 13:13 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""Has anyone tried taking the front grill off to see if that changes things? More air flow, more pressure against the radiator without the grill restriction? Just wondering..""
If you look at our packaging, there's a lot of crap in front of the radiator including the grille. Also, I wonder if some folks have bug screens in the way. Compared to cars, a huge part of our radiator sits behind and then below our bumpers as well.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Another fan clutch story [message #95698 is a reply to message #95693] |
Fri, 13 August 2010 13:33 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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This fan discussion is also beginning to parallel the vapor lock thread, Each has high variability and multiple inputs.
Dennis Sexton
73 PD 230
Germantown, TN
USA
-----Original Message-----
From: Bob de Kruyff <NEXT2POOL@AOL.COM>
To: gmclist@temp.gmcnet.org
Sent: Fri, Aug 13, 2010 1:10 pm
Subject: Re: [GMCnet] Another fan clutch story
""This whole discussion triggered a thought. This whole scenario is
nterrelated. Fan, Fan clutch, shroud, a/c condensor, oil and transmission
oolers, thermostat, pressure cap, coolant mix etc. There are so many
ariables that it is hard to consider all the possible cause and effects.
orta like the old adage, "When you are up to your butt in alligators, it is
ard to remember that the original objective was to drain the swamp."
bviously, the best radiator in the world can't do it's job if you can't
ove air through it and when the fan clutch cycles on in every case the temp
omes down. Seems like improved airflow is the short term answer. Just what
think.
im Hupy
alem, Or
8 Royale 403
" That's for sure--it's all a big system and maybe that's why so many of us
re seeing various results because the state of our individual parts of the
ystem are different. This continues to be one heck of a discussion.
-
ob de Kruyff
8 Eleganza
handler, AZ
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Another fan clutch story [message #95730 is a reply to message #95552] |
Fri, 13 August 2010 19:24 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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The higher temp stat will create a more stable temp range between sitting on partial stat and fan engagement. To me that's better than constantly heating and cooling the block temp.(poor man's heat treating) If you put a temp probe on the stat neck and one in the space between the rad and fan, it's pretty interesting to see how they track. The coolant remains within a few degs deviation while the air temp swings all over the place depending on driving conditions and speed and fan action. This "wild" signal is what the fan bimetalic is reading and probably the cause of what some think is erratic fan clutch behavior, when it is really not. As long as the clutch is intact mechanically, engages at cold startup and then free wheels shortly after, and comes on when needed, the small variences from unit to unit will always be there. Go down the aisle at the hardware and look at all the bimetalic rotary thermometers, no 2 will read the same and there is usually 5 degs variance to say the least.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Another fan clutch story [message #95736 is a reply to message #95730] |
Fri, 13 August 2010 19:48 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""As long as the clutch is intact mechanically, engages at cold startup and then free wheels shortly after, and comes on when needed, the small variences from unit to unit will always be there. Go down the aisle at the hardware and look at all the bimetalic rotary thermometers, no 2 will read the same and there is usually 5 degs variance to say the least. ::
John--a couple of thoughts. The fan coming on when cold is what's called "morning sickness" and is not an intended characteristic. The OEMs have pushed suppliers with moderate success to eliminate that because it is a huge customer concern. Because of that, many fan clutches will not come on when cold and it should never be considered as an indication whether the clutch is working correctly in other regions. The other point is that these clutches are varying more than than a few degrees. Many folks, including myself are seeing clutches that don't come on at all till 220F and the same clutch number on the same coach coming on at 185F. That is not the nature of the beast--just plain poor quality control.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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