Radiator/Shroud Problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**DANTIP** · 06-22-2011, 06:22 PM

I helped diagnose a cooling problem that only occurred at idle with the A/C on. This truck had all new cooling parts (radiator, hoses, water pump, thermostat, clutch fan, etc.). The truck would overheat in traffic.

I received a picture like this one (I chose this one because the gap is so evident) and was able to help the owner diagnose the problem. Notice the poor fit of the shroud to the radiator (you can see the fan clutch through the gap). At idle, the only air going through the radiator was being pulled by the fan. The air is going to follow the path of least resistance. The gap shown is an example of how an aftermarket radiator may not fit the shroud properly. The truck would do fine on the highway with the A/C on but at low speed, when the fan was supposed to be pulling air across the condenser then through the radiator, too much air was sneaking through the unintended gaps between the radiator and shroud. Another cause of this would be incorrect radiator mounts (4-core mounts with a 3-core radiator for example).

Long-Story-Short, make sure this gap is very narrow or find some way of sealing it up. Otherwise you can expect low-speed cooling problems.

**leddzepp** · 06-22-2011, 06:34 PM

people dont often realize how important a shroud is to a cooling system.
Posted via Mobile Device

MagmaJct · 06-23-2011, 07:35 AM

Good one. I was just involved in a discussion on this board where the owner was considering going to a colder thermostat to solve this very issue. Eventually he revealed he had no shroud because it wouldn't fit the fan. (Fan was too big.) Unfortunately, I'm heading out the door and have no time to link to the thread. (I can type faster than I can find the thread.)

Cheers!

**D.PASSMORE** · 06-23-2011, 02:16 PM

Something that I looked at numerous times is; the lenght of the After Market clutch fans. I have a OE one that went inop and purchased a replacement for NAPA. The shaft was about a 1/4" shorter in length than the OE. I looked at a couple different brands and all have the same diminsions. I don't like the fan sitting a 1/4" further out of the shroud. Beside inserting a spacer, haven't figured that one out.

**Classic Heartbeat** · 06-23-2011, 04:46 PM

The picture looks like they are using the wrong radiator clamps. They look to be 4 row clamps on a 3 row radiator. WES

elf w/capital T · 06-23-2011, 04:54 PM

...i know its ghetto but it works and looks clean, i cut a piece of metal, and bent it and it covers that little gap and is just flat.... just my two cents, good luck

06-22-2011, 06:22 PM	#1
DANTIP Registered User Join Date: Sep 2001 Location: Fort Wayne, Indiana, USA Posts: 1,890	Radiator/Shroud Problem I helped diagnose a cooling problem that only occurred at idle with the A/C on. This truck had all new cooling parts (radiator, hoses, water pump, thermostat, clutch fan, etc.). The truck would overheat in traffic. I received a picture like this one (I chose this one because the gap is so evident) and was able to help the owner diagnose the problem. Notice the poor fit of the shroud to the radiator (you can see the fan clutch through the gap). At idle, the only air going through the radiator was being pulled by the fan. The air is going to follow the path of least resistance. The gap shown is an example of how an aftermarket radiator may not fit the shroud properly. The truck would do fine on the highway with the A/C on but at low speed, when the fan was supposed to be pulling air across the condenser then through the radiator, too much air was sneaking through the unintended gaps between the radiator and shroud. Another cause of this would be incorrect radiator mounts (4-core mounts with a 3-core radiator for example). Long-Story-Short, make sure this gap is very narrow or find some way of sealing it up. Otherwise you can expect low-speed cooling problems. Attached Images

06-22-2011, 06:34 PM	#2
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,115	Re: Radiator/Shroud Problem people dont often realize how important a shroud is to a cooling system. Posted via Mobile Device __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man RIP FleetsidePaul

06-23-2011, 07:35 AM	#3
MagmaJct Registered User Join Date: May 2008 Location: Mesa, AZ Posts: 281	Re: Radiator/Shroud Problem Good one. I was just involved in a discussion on this board where the owner was considering going to a colder thermostat to solve this very issue. Eventually he revealed he had no shroud because it wouldn't fit the fan. (Fan was too big.) Unfortunately, I'm heading out the door and have no time to link to the thread. (I can type faster than I can find the thread.) Cheers!

06-23-2011, 02:16 PM	#4
D.PASSMORE One of the First Join Date: Jan 2000 Location: St. Augustine,FL. Posts: 4,060	Re: Radiator/Shroud Problem Something that I looked at numerous times is; the lenght of the After Market clutch fans. I have a OE one that went inop and purchased a replacement for NAPA. The shaft was about a 1/4" shorter in length than the OE. I looked at a couple different brands and all have the same diminsions. I don't like the fan sitting a 1/4" further out of the shroud. Beside inserting a spacer, haven't figured that one out. __________________ DAVID PASSMORE ST AUGUSTINE ,FL ZIP 32084 '71 SWB K/10 CUSTOM DELUXE (Chili) '72 BLAZER K/5 Muscle Truck (Mule) '72 LWB K/20 CHEYENNE (Blackie)

06-23-2011, 04:46 PM	#5
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,766	Re: Radiator/Shroud Problem The picture looks like they are using the wrong radiator clamps. They look to be 4 row clamps on a 3 row radiator. WES __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys

06-23-2011, 04:54 PM	#6
elf w/capital T Registered User Join Date: Feb 2011 Location: North Carolina Posts: 994	Re: Radiator/Shroud Problem ...i know its ghetto but it works and looks clean, i cut a piece of metal, and bent it and it covers that little gap and is just flat.... just my two cents, good luck

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