Beating a dead horse

T

Thigh19

New member
Aug 4, 2019
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I know this has been done more times than not, but I need to understand why electric radiator fans are bad. I have a Rambler American with an
overbuilt AMC 401. Only running an electric fan with an electric water pump. It cools fine, but only drive it a few miles to shows and the track
occasionally.
I’d like to run a couple pusher fans on the front of the radiator and leave the clutch fan behind the radiator. Everyone on here pretty much say
electric fans don’t work, but no one says why.
On another note, Has anybody used Water Wetter or Royal Purple Ice to there coolant systems? I’ve used it in performance vehicles with good results.
15 to 20 degrees drop in temperatures
 
Tom,

I'm not positive of the number, but I've heard that the big 7 bladed fan on
the GMC can pull as much as 8 HP from the engine. If you could get a 12
VDC 8 HP electric motor to drive your (big) fan, it might cool the engine
just as well. (But remember that 8HP= 746 Watts which is 8*746/12=497
Amps! Don't know where you're gonna get that from -- or even 1/2 of it!)

An electric fan can, when running, supplement the engine-driven fan. BUT,
when that same fan is not running, it's rotated by the aerodynamic forces
acting on it and becomes almost like an equally-sized flat plate
obstructing flow through the radiator. :-(

Ken H.

On Tue, Aug 18, 2020 at 1:47 PM Thom High via Gmclist <

> I know this has been done more times than not, but I need to understand
> why electric radiator fans are bad. I have a Rambler American with an
> overbuilt AMC 401. Only running an electric fan with an electric water
> pump. It cools fine, but only drive it a few miles to shows and the track
> occasionally.
> I’d like to run a couple pusher fans on the front of the radiator and
> leave the clutch fan behind the radiator. Everyone on here pretty much say
> electric fans don’t work, but no one says why.
> On another note, Has anybody used Water Wetter or Royal Purple Ice to
> there coolant systems? I’ve used it in performance vehicles with good
> results.
> 15 to 20 degrees drop in temperatures
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
basically you are taking the issues of having a mechanical fan, and putting those to an electrical system. electric fan systems end up either not
enough air flow, or they cause way too much headaches with fan belts and alternators and wiring.

I don't get people's issues and why they "want" to install electric fan. if you are running hot and think an electric fan is going to solve that,
you have other issues. if you want to do it, just because?? that is up to you, but why?

people are driving GMC's in Arizona and florida all the time and not overheating. I personally have a newer radiator, and mechanical fan and clutch
installed 2 years ago, 195 thermostat, and I have yet to see any water temps above 203(efi computer reading) My engine runs between 198 and 203
even when towing up a mountain grade at 90 degrees ambient.

I used to fight keeping engine cool, tried different theromstats, (180 was a mistake- huge temps swings) but the bottom line was my radiator was old
and not doing it's job.

Usually it is a old radiator causing any overheating problems.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Big dumb typo on my part: "...remember that 8HP= 746 Watts..." should have
read: "...remember that 8HP = 8*746 Watts..."

Ken H.

On Tue, Aug 18, 2020 at 2:19 PM Ken Henderson
wrote:

> Tom,
>
> I'm not positive of the number, but I've heard that the big 7 bladed fan
> on the GMC can pull as much as 8 HP from the engine. If you could get a 12
> VDC 8 HP electric motor to drive your (big) fan, it might cool the engine
> just as well. (But remember that 8HP= 746 Watts which is 8*746/12=497
> Amps! Don't know where you're gonna get that from -- or even 1/2 of it!)
>
> An electric fan can, when running, supplement the engine-driven fan. BUT,
> when that same fan is not running, it's rotated by the aerodynamic forces
> acting on it and becomes almost like an equally-sized flat plate
> obstructing flow through the radiator. :-(
>
> Ken H.
>
>
> On Tue, Aug 18, 2020 at 1:47 PM Thom High via Gmclist <

>
>> I know this has been done more times than not, but I need to understand
>> why electric radiator fans are bad. I have a Rambler American with an
>> overbuilt AMC 401. Only running an electric fan with an electric water
>> pump. It cools fine, but only drive it a few miles to shows and the track
>> occasionally.
>> I’d like to run a couple pusher fans on the front of the radiator and
>> leave the clutch fan behind the radiator. Everyone on here pretty much say
>> electric fans don’t work, but no one says why.
>> On another note, Has anybody used Water Wetter or Royal Purple Ice to
>> there coolant systems? I’ve used it in performance vehicles with good
>> results.
>> 15 to 20 degrees drop in temperatures
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
 
I have reviewed many electric fan units people put on the coaches. Few came
close to doing what the origioan fan with fan clutch did.
I design Fan/Blowers for the HVAC industry and know what it takes to do
them.
The coach is no more different, except at the higher end, it falls short.
Spal has the best published data to use as they have charts that have not
only free flow, but restricted flow.
Freeflow tells me half of what is required to pull air through a thick
radiator.
I compare data with a firm that provide One ton trucks that haul a 5th
wheelers and they cautioned me that on a long grade, the best fan
stillfall short on a hot day.
These fans were well shrouded and distanced for max flow.

On Tue, Aug 18, 2020 at 2:09 PM Ken Henderson via Gmclist <

> Big dumb typo on my part: "...remember that 8HP= 746 Watts..." should have
> read: "...remember that 8HP = 8*746 Watts..."
>
> Ken H.
>
>
>
> On Tue, Aug 18, 2020 at 2:19 PM Ken Henderson

>
> > Tom,
> >
> > I'm not positive of the number, but I've heard that the big 7 bladed fan
> > on the GMC can pull as much as 8 HP from the engine. If you could get a
> 12
> > VDC 8 HP electric motor to drive your (big) fan, it might cool the engine
> > just as well. (But remember that 8HP= 746 Watts which is 8*746/12=497
> > Amps! Don't know where you're gonna get that from -- or even 1/2 of it!)
> >
> > An electric fan can, when running, supplement the engine-driven fan.
> BUT,
> > when that same fan is not running, it's rotated by the aerodynamic forces
> > acting on it and becomes almost like an equally-sized flat plate
> > obstructing flow through the radiator. :-(
> >
> > Ken H.
> >
> >
> > On Tue, Aug 18, 2020 at 1:47 PM Thom High via Gmclist <

> >
> >> I know this has been done more times than not, but I need to understand
> >> why electric radiator fans are bad. I have a Rambler American with an
> >> overbuilt AMC 401. Only running an electric fan with an electric water
> >> pump. It cools fine, but only drive it a few miles to shows and the
> track
> >> occasionally.
> >> I’d like to run a couple pusher fans on the front of the radiator and
> >> leave the clutch fan behind the radiator. Everyone on here pretty much
> say
> >> electric fans don’t work, but no one says why.
> >> On another note, Has anybody used Water Wetter or Royal Purple Ice to
> >> there coolant systems? I’ve used it in performance vehicles with good
> >> results.
> >> 15 to 20 degrees drop in temperatures
> >>
> >> _______________________________________________
> >> GMCnet mailing list
> >> Unsubscribe or Change List Options:
> >> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >>
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
I suppose if you are concerned about the parasitic power loss from the
fan when unneeded an electric clutch would accomplish all that you are
looking to do.  If you want cooling after the engine is shut off, then
the electric fan makes sense to me.

The after-shutdown cooling isn't something I've ever given much thought
to, however.

> I know this has been done more times than not, but I need to understand why electric radiator fans are bad. I have a Rambler American with an
> overbuilt AMC 401. Only running an electric fan with an electric water pump. It cools fine, but only drive it a few miles to shows and the track
> occasionally.
> I’d like to run a couple pusher fans on the front of the radiator and leave the clutch fan behind the radiator. Everyone on here pretty much say
> electric fans don’t work, but no one says why.
> On another note, Has anybody used Water Wetter or Royal Purple Ice to there coolant systems? I’ve used it in performance vehicles with good results.
> 15 to 20 degrees drop in temperatures
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Larry Davick
ljdavick
 
Not to contradict any of the given advice and information.

However I found it personally interesting that I had two old school AC specialist tell me that a pusher fan when used as a supplement support for an
over worked AC system was a very valid solution.

Keep in mind both of these two guys had absolutely no knowledge of GMC MHs and their characteristics. They were coming from a strictly AC industry
point of view and this was a practice done to alleviate issues on many vehicles they worked on. These two do not know each other, in fact from two
different countries. I just found it interesting they had offered up the same solution to address the same type issues.

Pusher fan goes in front of the condenser and is wired to come on then the ac compressor kicks in.
--
Jim Owens,

78 Royale,

Out skirts of Kitchener, Ontario
 
That pusher might help with lowering AC head pressure in stopped traffic on a school bus. But would most likely reduce cooling at road speed. My
GMC with stock clutch fan and shroud set up has no problem with maintaining thermostat set temp at idle with AC on. The problem is that above 70 MPH
the high pressure in the engine room impedes natural air flow and the high fuel rate produces heat that is hard to shed.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
I went through the trouble of adding two electric fans in front of
my external oil cooler and AC condenser. I do notice that the fan clutch
does not kick on when driving in slow traffic with the electric fans on.
So it seems to help with additional cooling.

Just my 2¢
--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
Outlet vents at the trailing edges of the front wheel wells.

D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com

________________________________
From: Gmclist on behalf of John R. Lebetski via Gmclist
Sent: Tuesday, August 18, 2020 21:13
To: gmclist
Cc: John R. Lebetski
Subject: Re: [GMCnet] Beating a dead horse

That pusher might help with lowering AC head pressure in stopped traffic on a school bus. But would most likely reduce cooling at road speed. My
GMC with stock clutch fan and shroud set up has no problem with maintaining thermostat set temp at idle with AC on. The problem is that above 70 MPH
the high pressure in the engine room impedes natural air flow and the high fuel rate produces heat that is hard to shed.
--
John Lebetski
Woodstock, IL
77 Eleganza II

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> I suppose if you are concerned about the parasitic power loss from the fan when unneeded an electric clutch would accomplish all that you are
> looking to do.  If you want cooling after the engine is shut off, then the electric fan makes sense to me.
>
> The after-shutdown cooling isn't something I've ever given much thought to, however.
> --
> Larry Davick

Larry,

If one is concerned about the after shutdown conditions, an electric fan is still not an answer. In Dynoland with expensive hand built engines that
have 27 (more or less) thermocouples, we would always watch a new engine for the shutdown temperature spike. There can be "interesting" problems
cause by the residual heat in the cylinder head casting around the exhaust ports. This can cause real problems with engines with Siamese cylinder
liners. (That is what a 403 has, no space for cooling between the cylinders.) The problem is that the thermal expansion can crush the gasket in that
area.
If a new family showed a bad tendency this way, I would always write a 10/10 (10 MAP{20"vac}@1000) cooldown into the engine test plan. While I will
be the first to tell you that nothing good happens to an engine that is idling, sometimes it is the best answer for a hot engine.

Matt - the refugee from Dynoland
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Has anyone actually measured the pressure and compared it to any other vehicle or before and after adding the vents behind the front wheel wells?

Has anyone actually measured the underhood temperature before and after adding the vents behind the front wheel wells?

Rick M.


> Outlet vents at the trailing edges of the front wheel wells.
>
> D C "Mac" Macdonald
> Amateur Radio K2GKK
> Since 30 November '53
> USAF and FAA, Retired
> Member GMCMI & Classics
> Oklahoma City, OK
> "The Money Pit"
> TZE166V101966
> '76 ex-Palm Beach
> k2gkk + hotmail dot com
>
> ________________________________
> From: Gmclist on behalf of John R. Lebetski via Gmclist
> Sent: Tuesday, August 18, 2020 21:13
> To: gmclist
> Cc: John R. Lebetski
> Subject: Re: [GMCnet] Beating a dead horse
>
> That pusher might help with lowering AC head pressure in stopped traffic on a school bus. But would most likely reduce cooling at road speed.
> My
> GMC with stock clutch fan and shroud set up has no problem with maintaining thermostat set temp at idle with AC on. The problem is that above 70
> MPH
> the high pressure in the engine room impedes natural air flow and the high fuel rate produces heat that is hard to shed.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
1974 26' Canyonlands
aka "The General"
Clinton, TN
 
Aw geez, now he is going to get all scientific on us. I have the stainless
steel louvers on my 1978 Royale. They are located almost under the gasoline
filler door, just below the top of the inner fenders. When I stop for fuel,
and stand there monitoring the filler hose, the underhood heat just pours
out of those louvers. I don't care much about the air temps, just that the
damn things work, and very well. I know that the heat must just come
streaming out of them when the coach is underway. Again, I have no idea how
many cubic feet per minute pass through those louvers, or the temperature
it is. Some must be better than none at all. That is my take on it. Other
opinions will vary.
Jim Hupy
Salem, Oregon

On Thu, Aug 20, 2020, 6:59 PM Richard Michelhaugh via Gmclist <

> Has anyone actually measured the pressure and compared it to any other
> vehicle or before and after adding the vents behind the front wheel wells?
>
> Has anyone actually measured the underhood temperature before and after
> adding the vents behind the front wheel wells?
>
> Rick M.
>

> > Outlet vents at the trailing edges of the front wheel wells.
> >
> > D C "Mac" Macdonald
> > Amateur Radio K2GKK
> > Since 30 November '53
> > USAF and FAA, Retired
> > Member GMCMI & Classics
> > Oklahoma City, OK
> > "The Money Pit"
> > TZE166V101966
> > '76 ex-Palm Beach
> > k2gkk + hotmail dot com
> >
> > ________________________________
> > From: Gmclist on behalf of John R. Lebetski via Gmclist
> > Sent: Tuesday, August 18, 2020 21:13
> > To: gmclist
> > Cc: John R. Lebetski
> > Subject: Re: [GMCnet] Beating a dead horse
> >
> > That pusher might help with lowering AC head pressure in stopped
> traffic on a school bus. But would most likely reduce cooling at road
> speed.
> > My
> > GMC with stock clutch fan and shroud set up has no problem with
> maintaining thermostat set temp at idle with AC on. The problem is that
> above 70
> > MPH
> > the high pressure in the engine room impedes natural air flow and the
> high fuel rate produces heat that is hard to shed.
> > --
> > John Lebetski
> > Woodstock, IL
> > 77 Eleganza II
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> --
> 1974 26' Canyonlands
> aka "The General"
> Clinton, TN
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
All 3 coaches that I have owned or still own have the vent installed. This type vent system has been installed by owners since the coaches have been built. Jim H is right, you’re being too analytical. The vents do increase the air flow and allow the heat another path to exit the engine area. How much, it really doesn’t matter and they look cool (sorry) too!

This is an Installation sheet for typical installation.

http://www.gmcrvparts.com/v/vspfiles/images/side_vents.pdf

You can get several styles of these vents.

https://www.gmcrvparts.com/product-p/g14881.htm (From Jim K and most popular.)

https://www.westmarine.com/buy/west-marine--recessed-louvered-8-slot-vent--280746?recordNum=19 (this is from West Marine)

https://www.westmarine.com/buy/attwood--louvered-vents--P012_363_002_503?recordNum=7 (this one is plastic)

Regards,

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan

>
> Aw geez, now he is going to get all scientific on us. I have the stainless
> steel louvers on my 1978 Royale. They are located almost under the gasoline
> filler door, just below the top of the inner fenders. When I stop for fuel,
> and stand there monitoring the filler hose, the underhood heat just pours
> out of those louvers. I don't care much about the air temps, just that the
> damn things work, and very well. I know that the heat must just come
> streaming out of them when the coach is underway. Again, I have no idea how
> many cubic feet per minute pass through those louvers, or the temperature
> it is. Some must be better than none at all. That is my take on it. Other
> opinions will vary.
> Jim Hupy
> Salem, Oregon
>
> On Thu, Aug 20, 2020, 6:59 PM Richard Michelhaugh via Gmclist <

>
>> Has anyone actually measured the pressure and compared it to any other
>> vehicle or before and after adding the vents behind the front wheel wells?
>>
>> Has anyone actually measured the underhood temperature before and after
>> adding the vents behind the front wheel wells?
>>
>> Rick M.
>>

>>> Outlet vents at the trailing edges of the front wheel wells.
>>>
>>> D C "Mac" Macdonald
>>> Amateur Radio K2GKK
>>> Since 30 November '53
>>> USAF and FAA, Retired
>>> Member GMCMI & Classics
>>> Oklahoma City, OK
>>> "The Money Pit"
>>> TZE166V101966
>>> '76 ex-Palm Beach
>>> k2gkk + hotmail dot com
>>>
>>> ________________________________
>>> From: Gmclist on behalf of John R. Lebetski via Gmclist
>>> Sent: Tuesday, August 18, 2020 21:13
>>> To: gmclist
>>> Cc: John R. Lebetski
>>> Subject: Re: [GMCnet] Beating a dead horse
>>>
>>> That pusher might help with lowering AC head pressure in stopped
>> traffic on a school bus. But would most likely reduce cooling at road
>> speed.
>>> My
>>> GMC with stock clutch fan and shroud set up has no problem with
>> maintaining thermostat set temp at idle with AC on. The problem is that
>> above 70
>>> MPH
>>> the high pressure in the engine room impedes natural air flow and the
>> high fuel rate produces heat that is hard to shed.
>>> --
>>> John Lebetski
>>> Woodstock, IL
>>> 77 Eleganza II
>>>
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>>
>> --
>> 1974 26' Canyonlands
>> aka "The General"
>> Clinton, TN
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
My first GMC has an 3" axial blower fan installed that exhausted from the engine compartment through the installed driver's side vent. P.O. had an
complicated thermostat and relay controlled on and off system. I removed that undefined mess and replaced it with a switch, triggering a power relay,
operated from the driver's seat. Flip the switch, and see your temperature gauge drop and fast. Helped out here in the Deep South. For the $15 the
fans cost, might be worth trying.
Tom
--
2012 Phoenix Cruiser model 2552
KA4CSG
 
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