Gets hot after adding shroud?

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L31MaxExpress

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"Electric" fan: I would pay good money to see someone retrofit one of the electric clutches, to one of the GMT400s.

Here's Hayden's selection:


The Chevy Trailblazer used an electric fan clutch (and presumably GMC / Saab / Oldsmobile / Buick / Isuzu cloans) on some (all?) of its engines. It had the 4.2L I5 and the 5.3L V8, right? Was the "SS" a 5.3L too?

I finished that retrofit actually Friday afternoon. Van stays 185F now on the dot. Its controlled off fan 2 output on the LS PCM, via a relay. The 6.0 LS2 powered the SS and that is what my Hayden was built to replace. Its a severe duty and turns about 50-60% when it is commanded off and about 80-90% when it is on.

A guy on the Express/Savanna group I follow put one on from a 6.6L Van on a 6.5L van. I mounted mine the same way. My van has a newer 3 wire pressure sensor on it. When the ac pressure exceeds Fan 2 setting right after startup the clutch fully engages 5-6 seconds after. Once I am driving around for a few minutes and the interior cools down the pressure drops and the fan clutch releases. The 16" electric puller and the freewheeling clutch have been enough to keep the ac ice cold and the engine at 185F on the dot.

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1998_K1500_Sub

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Converted to 16" electric fan a couple of years ago after the water pump mount sheared and about threw the mechanical fan through my face.


Here's a line-by-line explanation, responding to each of your points:

Cooled fine at speed without a shroud,

(1) Makes sense. The vehicle's speed generated air pressure in front of the radiator. There were no (unusual) impediments to airflow in front or behind the radiator, so there was ample airflow through the radiator. The engine stayed cool.

wants to get hot after driving on the freeway and pulling off.

(2) Makes sense. Vehicle's speed is now low (zero?), so there's not much air pressure in front of the radiator. Consequently, the air flow through the radiator decreases and the engine heat's not carried away. Engine temps increase.

Thought it was the lack of shroud so I made one from thin gauge. Made it 5 miles with the shroud and it's getting hot.

(3) Makes sense. At speed, there's still air pressure in front of the radiator like before, but now the shroud behind the radiator impedes the flow of air through the radiator. So (unlike before) there's no longer enough air flow through the radiator. The engine temps increase.

Fan seems to move a ton of air.

(4) Evidently, not enough, although certainly it's moving more through the radiator than it did before, now that you've put the shroud on... just not enough.

But why would adding a shroud make it get hot at slower city speed where it didn't without a shroud at all?

See (3) above.
 
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454cid

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The Chevy Trailblazer used an electric fan clutch (and presumably GMC / Saab / Oldsmobile / Buick / Isuzu cloans) on some (all?) of its engines. It had the 4.2L I5 and the 5.3L V8, right? Was the "SS" a 5.3L too?

Close, it was the Inline 6 and the V8. The Colorado got the 5cyl.... and I think a 4cyl, too.

I don't know much about the Atlas engines, but I've kinda wanted the I6 engine for awhile. I guess I wouldn't mind one of the 5cyl engines, too.... may as well since I've got an I5 Volvo.
 

BeXtreme

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I had the same fans, they would not keep my engine cool. My radiator was a 454/8.1 core. Ambient air in bumper to bumper is 118F at the moment, its 109F in the shade. Who said Texas is level?
Texas is flat... look at a topographical map. Its not hundreds of miles of corn Kansas flat, but there is no real elevation to speak of. You have lots of rolling hills, but they are inconsequential compared to big mountain passes. I lived in Texas for 5 years.

You had something wrong there. It was 118 here last year, no issues. The pic with it hooked to the trailer was with the old 1970 350/TH400/205 combo in it with the 97 454 radiator/electric fan combo and no overheating issues at all. It now has an L29/454 combo converted to CNP and 0411 and still no issues with cooling at all. AC works way better with the electric fans than it did with the mechanical because it is pulling way more air through the radiator at idle than the mechanical did. Fan blades are designed to have maximum efficiency at a specific RPM. Mechanical fans are tied to the RPM of the engine, electric fans are always operating at the correct RPM for maximum efficiency.
 

L31MaxExpress

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Texas is flat... look at a topographical map. Its not hundreds of miles of corn Kansas flat, but there is no real elevation to speak of. You have lots of rolling hills, but they are inconsequential compared to big mountain passes. I lived in Texas for 5 years.

You had something wrong there. It was 118 here last year, no issues. The pic with it hooked to the trailer was with the old 1970 350/TH400/205 combo in it with the 97 454 radiator/electric fan combo and no overheating issues at all. It now has an L29/454 combo converted to CNP and 0411 and still no issues with cooling at all. AC works way better with the electric fans than it did with the mechanical because it is pulling way more air through the radiator at idle than the mechanical did. Fan blades are designed to have maximum efficiency at a specific RPM. Mechanical fans are tied to the RPM of the engine, electric fans are always operating at the correct RPM for maximum efficiency.
Yea what was wrong is the electric fans do not move near the CFM of the clutch fan. My clutch fan cools better everywhere including at idle than the Tahoe fans. I had 13.8 volts on the system and 13.5 volts across the fans back probing them on high speed. Problem was purely the fans in my case. Clutch fan moves way more airflow even at idle. It will stick a shop rag to the grille over a foot away at idle. At 2,000-3,000 rpm the clutch fan moves in excess of 10,000 cfm, something the electrics cannot do. My cooling issue was never at idle, it was always climbing a long grade at speed or pulling uphill at slower speeds or in bumper to bumper traffic with constant stop and go. My 8.1L Tahoe has a clutch fan on it too and you could kick back and take a nap in the ice cold ac while the engine sits at 185°F.

My uncle towed his travel trailer into Colorado this summer with a bone stock 2017 6.2L Denali 4x4 crew cab. It went into reduced power mode and shut the ac off numerous times on the grades. Its about to get a clutch fan on it.
 
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Jeepwalker

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Why not go back to a stock OEM fan and stock shroud (or an OEM fan with a few more blades, like a 9 or 11 blade -- tahoe)? Get a quality (OEM) fan clutch, not a cheapie. Make sure the fan is at the correct depth into the shroud (not too far in or out). Mine's never overheated with a stock fan. Don't buy a flimsy part's store 'flex fan' (they're weak, don't always move a lot of air ...and prone to breakage) ...get a stock GM fan from the salvage yard. Make sure your radiator isn't limed up inside (else soak with radiator cleaner). Ensure your truck has good 'clean' airflow straight through the fan/condenser ...no winch or lights in front of the radiator blocking airflow.

Electric fans take juice to run and put drag on your alternator ....adding drag to your engine. That's going to add heat and a mileage penalty. There's no free lunch when it comes to energy moving air.

Classic Corvette guys go through this all the time with trying to cool Big block or built-up engines. After trying all sorts of electric fans, a lot of owners go back to a stock fan. The key is to make sure it's the right diameter, the right depth and (for Corvettes) ensure the factory foam is around the fan shroud to seal it tight against the radiator (to prevent air from short-cycling around the shround ...and pulling all air through the radiator).

Couple other things to check: Obviously make sure your thermostat is working 'right' and your timing is correct. Also, I've seen in the past where a water pump works when the vehicle is cold (impeller 'tight' on the shaft), but spins freely on the shaft once the coolant gets hot (impeller expands and spins free). It's rare, but not out of the question. Also make sure the lower radiator hose has a spring in it and isn't 'sucking-in' on itself ...at road speed (another hidden factor which can heat up an engine at highway rpms).

Good luck
 
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mattillac

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......But why would adding a shroud make it get hot at slower city speed where it didn't without a shroud at all? Thoughts?

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Seems like a good candidate for some shroud flaps.

:33:

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Assuming that your fan isn't constantly powered (always running) and that you are using some sort of coolant temperature controlled device to operate it.

But if the fan is wired to be constantly ON then I would say your fan and/or shroud design just can't keep up with your cooling needs.

Wants to ".....get hot after driving on the freeway and pulling off...." sounds normal to me, that is when I would expect my electric fans to kick ON (stop and go traffic).

Best of luck.
 

L31MaxExpress

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Why not go back to a stock OEM fan and stock shroud (or an OEM fan with a few more blades, like a 9 or 11 blade -- tahoe)? Get a quality (OEM) fan clutch, not a cheapie. Make sure the fan is at the correct depth into the shroud (not too far in or out). Mine's never overheated with a stock fan. Don't buy a flimsy part's store 'flex fan' (they're weak, don't always move a lot of air ...and prone to breakage) ...get a stock GM fan from the salvage yard. Make sure your radiator isn't limed up inside (else soak with radiator cleaner). Ensure your truck has good 'clean' airflow straight through the fan/condenser ...no winch or lights in front of the radiator blocking airflow.

Electric fans take juice to run and put drag on your alternator ....adding drag to your engine. That's going to add heat and a mileage penalty. There's no free lunch when it comes to energy moving air.

Classic Corvette guys go through this all the time with trying to cool Big block or built-up engines. After trying all sorts of electric fans, a lot of owners go back to a stock fan. The key is to make sure it's the right diameter, the right depth and (for Corvettes) ensure the factory foam is around the fan shroud to seal it tight against the radiator (to prevent air from short-cycling around the shround ...and pulling all air through the radiator).

Couple other things to check: Obviously make sure your thermostat is working 'right' and your timing is correct. Also, I've seen in the past where a water pump works when the vehicle is cold (impeller 'tight' on the shaft), but spins freely on the shaft once the coolant gets hot (impeller expands and spins free). It's rare, but not out of the question. Also make sure the lower radiator hose has a spring in it and isn't 'sucking-in' on itself ...at road speed (another hidden factor which can heat up an engine at highway rpms).

Good luck

Good points made although I am not a fan of the factory clutch at all. When disengaged they slip too much requiring it to fully engage too often and for too long. In hot weather and hard to cool setups the severe duty clutch is better. It idles the fan at a higher rpm and prevents it from fully engaging as often if ever.

That being said I really like the severe duty electric clutch I put on mine, I use the PCM to set when it fully engages and have near full control of when it kicks in. So far even in 111F it only kicks in with ac pressure when the interior is heat soaked. My ac was cooling 38F out of the center vent in 111F yesterday. I adjusted my idle in Park/Neutral with the a/c on to hold 1,150 rpm until the engine hits 160°F. When I remote start it the idle kicks up and holds to help the initial cooldown. After hours of sunsoak the interior is already getting comfortable after 5 minutes of high idle. I have a windshield sun shade that is cut specifically for the van to use while parked but I am considering a heat rejecting clear film on the windshield as it is the hottest piece of glass on the whole van and the only piece of glass that does not have heat rejecting tint.
 
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