Stock Radiator Fan - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SanJosesSteve · 08-02-2017, 12:21 PM

So I finally got the nerve to take the 59 GMC on my annual fishing trip. 250 mile round trip from sea level up to 10,000' and back. All original... (less the dual M/C and fog lights I just converted to.)... 270 motor (130K) , single Zenith carb, 3 on the tree and a stump puller of a rear end.

Temps across the valley hit 105 and the gage was kissing the edge of the normal range while maintaining 60mph. With a bit of a grade ahead of me I turned on the heater. The truck never over heated, but I was dying until I got up to 3,000' and the outside temp started to cool.

A friend suggested that I may be able to swap my 4 blade fan for a 5 blade model. Maybe a water pump with a smaller hub or a shroud for the radiator.

I like the fact that the truck is all original and so want to limit the scope of any mods, like an electric fan. Would there be any gain to a 5 blade fan?

Thanks, Steve

Jemezcrusher · 08-02-2017, 12:55 PM

It might, but at speed the fan does not do that much cooling. The radiator should be able to cool it without a fan at all going down the road.

Was not uncommon at all to see cars pulled over in the mountains in the 60's Just part of the drill.

_Ogre · 08-02-2017, 01:05 PM

me personally thinks that your stock truck performed exceptional in 105* temps
not sure anything you do to it will make it run cooler climbing a grade like that in those temps
a real temp gauge with numbers rather than H---C might give you acurate readings too
even if it's wired temporarily wire tied under the dash

if you did that climb regularily in those temps a wiper washer pump spraying in front of the radiator would drop the temp gauge
my 56 chevy 48 pass schoolbus/camper had a similar problem on long grades in high temps
i carried a couple gallons of water and would use one gallon to cool the motor before shutdown

SanJosesSteve · 08-02-2017, 01:49 PM

Hummm..... Actually I had thought about spraying myself with water! Never thought about spraying the radiator. I'm going to repeat this trip next weekend. Will look into setting up a temporary "radiator wash" system for when the temp spikes.

With the heater on, it was really HOT in the cab. Lucky it even has a heater. My grandfather told me when he bought it brand new, it didn't come with one! Said he drove it 2 years before going back to the dealer and having them put the heater in....... Ha!

Thanks for the tip! -Steve

1project2many · 08-02-2017, 02:42 PM

It would be hard to hide, but an air dam below the radiator could make a big difference in cooling. If you can create a low pressure area below the engine it will "pull" more air through the radiator and out the bottom. Without the low pressure assistance the air sort of puddles up under the hood.

Another possibility is to add an oil cooler. It's a quiet and subtle modification and it will help removing engine heat.

It may be possible to change spark timing and fuel/air mix to improve overheating as well. The settings were determined with fuel used in the '50s. Today's gasoline is very different and in some cases you can advance spark and / or change mixture and see an improvement.

**mr48chev** · 08-02-2017, 05:14 PM

A five blade fan might not help a huge amount but it sure won't hurt anything especially on the long pulls.

I go along with having a real mechanical temp gauge and the oil cooler isn't a bad idea.
If the truck has the external oil filter it might be real easy to run a couple of lines to and from an oil cooler placed up in front of the radiator.
Still that truck did a lot better than a lot of other rigs might. I'd say your cooling system is pretty efficient even with running the heater for added cooling. I've done that on a couple of late model rigs that heated up in certain situations..

Second Series · 08-03-2017, 11:10 AM

Do you have a fan shroud? My truck ran hot in Texas and it didn't have a shroud. I put one in and the temps went down considerably.

SanJosesSteve · 08-03-2017, 11:38 AM

No fan shroud in my GMC. I've never seen one for sale for a 6 cyl powered truck, only the V8 models. If it came with one originally, I would think Gramps would have kept it there. I suppose one would fit...... I'm kinda intrigued by the washer pump spraying the radiator idea.

Maybe install a mister in the cab to keep me cool too. Driving down that mountain pass with all drum brakes really had my metabolism up! Hahahaha! -SF

1project2many · 08-03-2017, 12:02 PM

Watch out for the mister, Mister. If you fill it with straight window washer fluid as folks sometimes suggest the methanol will do lots of bad things including turning into a highly flammable gas as it evaporates off the radiator. Potentially explosive...

The 2 ton and up trucks were sometimes available with fan shrouds. I had one many years ago.

08-02-2017, 12:21 PM	#1
SanJosesSteve Registered User Join Date: Aug 2007 Location: San Jose, CA Posts: 46	Stock Radiator Fan So I finally got the nerve to take the 59 GMC on my annual fishing trip. 250 mile round trip from sea level up to 10,000' and back. All original... (less the dual M/C and fog lights I just converted to.)... 270 motor (130K) , single Zenith carb, 3 on the tree and a stump puller of a rear end. Temps across the valley hit 105 and the gage was kissing the edge of the normal range while maintaining 60mph. With a bit of a grade ahead of me I turned on the heater. The truck never over heated, but I was dying until I got up to 3,000' and the outside temp started to cool. A friend suggested that I may be able to swap my 4 blade fan for a 5 blade model. Maybe a water pump with a smaller hub or a shroud for the radiator. I like the fact that the truck is all original and so want to limit the scope of any mods, like an electric fan. Would there be any gain to a 5 blade fan? Thanks, Steve Attached Images __________________ "What's that round short pedal on the floor do?"

08-02-2017, 12:55 PM	#2
Jemezcrusher Registered User Join Date: Nov 2015 Location: Jemez Springs, NM Posts: 435	Re: Stock Radiator Fan It might, but at speed the fan does not do that much cooling. The radiator should be able to cool it without a fan at all going down the road. Was not uncommon at all to see cars pulled over in the mountains in the 60's Just part of the drill.

08-02-2017, 01:05 PM	#3
_Ogre Registered User Join Date: Jan 2012 Location: Motown Posts: 7,680	Re: Stock Radiator Fan me personally thinks that your stock truck performed exceptional in 105* temps not sure anything you do to it will make it run cooler climbing a grade like that in those temps a real temp gauge with numbers rather than H---C might give you acurate readings too even if it's wired temporarily wire tied under the dash if you did that climb regularily in those temps a wiper washer pump spraying in front of the radiator would drop the temp gauge my 56 chevy 48 pass schoolbus/camper had a similar problem on long grades in high temps i carried a couple gallons of water and would use one gallon to cool the motor before shutdown __________________ cool, an ogre smiley Ogre's 58 Truk build how to put your truck year and build thread into your signature shop air compressor timer

08-02-2017, 01:49 PM	#4
SanJosesSteve Registered User Join Date: Aug 2007 Location: San Jose, CA Posts: 46	Re: Stock Radiator Fan Hummm..... Actually I had thought about spraying myself with water! Never thought about spraying the radiator. I'm going to repeat this trip next weekend. Will look into setting up a temporary "radiator wash" system for when the temp spikes. With the heater on, it was really HOT in the cab. Lucky it even has a heater. My grandfather told me when he bought it brand new, it didn't come with one! Said he drove it 2 years before going back to the dealer and having them put the heater in....... Ha! Thanks for the tip! -Steve __________________ "What's that round short pedal on the floor do?"

08-02-2017, 02:42 PM	#5
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,200	Re: Stock Radiator Fan It would be hard to hide, but an air dam below the radiator could make a big difference in cooling. If you can create a low pressure area below the engine it will "pull" more air through the radiator and out the bottom. Without the low pressure assistance the air sort of puddles up under the hood. Another possibility is to add an oil cooler. It's a quiet and subtle modification and it will help removing engine heat. It may be possible to change spark timing and fuel/air mix to improve overheating as well. The settings were determined with fuel used in the '50s. Today's gasoline is very different and in some cases you can advance spark and / or change mixture and see an improvement.

08-02-2017, 05:14 PM	#6
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,705	Re: Stock Radiator Fan A five blade fan might not help a huge amount but it sure won't hurt anything especially on the long pulls. I go along with having a real mechanical temp gauge and the oil cooler isn't a bad idea. If the truck has the external oil filter it might be real easy to run a couple of lines to and from an oil cooler placed up in front of the radiator. Still that truck did a lot better than a lot of other rigs might. I'd say your cooling system is pretty efficient even with running the heater for added cooling. I've done that on a couple of late model rigs that heated up in certain situations.. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

08-03-2017, 11:10 AM	#7
Second Series Registered User Join Date: May 2015 Location: Tukwila Washington Posts: 391	Re: Stock Radiator Fan Do you have a fan shroud? My truck ran hot in Texas and it didn't have a shroud. I put one in and the temps went down considerably.

08-03-2017, 11:38 AM	#8
SanJosesSteve Registered User Join Date: Aug 2007 Location: San Jose, CA Posts: 46	Re: Stock Radiator Fan No fan shroud in my GMC. I've never seen one for sale for a 6 cyl powered truck, only the V8 models. If it came with one originally, I would think Gramps would have kept it there. I suppose one would fit...... I'm kinda intrigued by the washer pump spraying the radiator idea. Maybe install a mister in the cab to keep me cool too. Driving down that mountain pass with all drum brakes really had my metabolism up! Hahahaha! -SF __________________ "What's that round short pedal on the floor do?"

08-03-2017, 12:02 PM	#9
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,200	Re: Stock Radiator Fan Watch out for the mister, Mister. If you fill it with straight window washer fluid as folks sometimes suggest the methanol will do lots of bad things including turning into a highly flammable gas as it evaporates off the radiator. Potentially explosive... The 2 ton and up trucks were sometimes available with fan shrouds. I had one many years ago.



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