cooling help

[gulfyankee]

This is an interesting topic, and good points are being brought up. To add, I wonder how much additional heat is created by the engine in powering the engine driven fan? I'm sure it requires a good bit of power to create that 100+ mph wind. I realize that alternators also create drag(and heat) when the electric fans would kick on, but at least up until that point, it would seem that the engine might not be creating quite as much heat. Just a thought.

 

[Franko914]

To address the initial post... one cheap and easy way of increasing heat transfer from the radiator fins to the air flow over them is to install a series of water spray nozzles in front of the radiator and use a windshield washer pump (for one or two nozzles) or a Flojet 12V pump (for several nozzles).

The nozzles can be wide fan pattern windshield washer nozzles (I like the ones that were installed on '86 Camaros) or fan/cone pattern nozzles used in water injection kits/farm spraying applications.

The spray droplets can be large which will cause them to "wet" the fins, absorb the heat, evaporate in the process and drop the coolant temperature PDQ. This is what I installed on my '81 CJ-7 two decades ago to complement/back up the open electric fan I installed to replace the engine mounted fan. Using winter windshield washer fluid worked the best because the methanol/water evaporated much quicker than just plain water (although water has a higher capacity to absorb heat).

The spray droplets can be fine to very fine (mist) which has the effect of absorbing heat from the surrounding air (can drop the temperature up to 20 degrees in ambient temperatures above 95 degF; sold as "patio cool mist systems") which will make the heat transfer from the fins to the air flowing over them even more efficient.

You can use an add-on radiator overflow tank as your water reservoir, or even tap off your windshield water reservoir if space is not available.

Spraying can be in 1-2 second bursts for large droplets (it is a sight to behold, seeing the steam come off the radiator fins and watching the temperature gauge drop), or 5-10 second bursts for mist spray.

Regards,
Franko

 

[Franko914]

This is an interesting topic, and good points are being brought up. To add, I wonder how much additional heat is created by the engine in powering the engine driven fan? I'm sure it requires a good bit of power to create that 100+ mph wind. I realize that alternators also create drag(and heat) when the electric fans would kick on, but at least up until that point, it would seem that the engine might not be creating quite as much heat. Just a thought.

The additional drag on the engine by the increased load on the alternator is much less than the additional drag by belt driven fan. The proof is in the improved mileage/less fuel used.

The major principle in action is that electric motors are more energy efficient than internal combustion engines (even in this situation when an engine-driven alternator is used to generate electrical energy to power the electric fan's motor).

Also, that "roar" of the engine-driven fan requires energy to produce (although in this case, it is a waste by-product, therefore a waste in energy, too).

 

[WarWagon]

Sure the electrics take less power. The move less air because of that. They do have a steady speed an in some cases work better at idle than the clutch fan. You can also turn them off to cross some deep water.

Electric fans take like 40 amps. The alternator is worth around 3HP at 140 amps. Most clutch fans take ~5-25 HP. You are not going to get that HP from an electric fan motor that fits under the hood.

The 2005+ GM Pickups 1500 series use electric fans. The HD, 2500 etc. still use clutch fans. The 2008 Duramax uses a monster 25" fan. This comes back to light duty use can get away with low CFM electrics. But when you put the load and/or trailer on the electrics can't move enough air to keep it cool under extreme conditions. Thus the HD trucks still have the clutch fan. (And many times with GM even that isn't enough cooling for normal conditions.)

In the case of the Trailblazer we added a thicker radiator because the thin factory unit would not "use" all of the airflow. Simply turning on the AC would heat the condenser to 160 degrees and engine ECT would hit 220 no matter the engine RPM or fan %. With a 1.5" vs less than 1" thick factory radiator the temps would come down to 176 - thermostat closing temp. (@2000 RPM full fan clutch lockup.) A thicker radiator will not help our rigs as I already asked Ron Davis about this. They said we, this body style, have an airflow problem where a thicker radiator will not help.

 

[Crankme69]

Increasing the surface area of the radiator won't help...that seems to go against all thermodynamic principles?

 

[Franko914]

Increasing the surface area of the radiator won't help...that seems to go against all thermodynamic principles?

It would seem so but as he stated, it's an airflow problem: if the air cannot flow easily, it will not flow easily.

I would start by:
(a) removing the splash guard or cutting it in places that would allow a better flow of air through the engine compartment;
(b) installing an air dam/spoiler under the front bumper if one isn't there yet;
(c) installing a couple of hood vents more towards the windshield (it will help with no/slow speed venting and, definitely, with high-speed venting because of the low pressure zone created in the area where the hood meets the windshield).

Improving the airflow by allowing a lower pressure zone behind the fan blades is the key -- if the air behind the fan blades have nowhere to go freely, it will not flow easily.

 

[WarWagon]

Exactly. Slow moving air is "saturated" with heat from the factory radiator. Saturated would be as close to coolant as possible before exiting the fins. A thicker radiator just adds restriction as the air would be the same temperature coming off the thicker radiator as it was from the factory unit.

However if you have excess airflow, where the factory radiator can't use it all. This would be air that is lower temp leaving the fins than the coolant and can still pick up heat. The thicker radiator, in this case, makes the air hotter leaving the radiator in effect cooling the engine better.

We have an aerodynamic front end and body design. And other things that did not encourage airflow through the radiator. May save us MPG with light loads. Other rigs like Dodges that get the same 'poor' fuel economy loaded or empty have better cooling because they take the MPG hit from the wind resistance and better radiator airflow - needed or not from load. Maybe a trade off was made: MPG for max cooling.

 

[Crankme69]

Thanks for the explanations on my larger surface area question.

If the original poster don't mind, (I Hope) I would like to use this post to answer a couple of additional questions I have about my 1995 ext cab long bed truck that is pictured in my avatar.

The 95 in my avatar had the front grille replaced from a fender bender by the previous owner. I have been considering replacing that current grille assembly, the current one in the pic I believe is from an earlier 90's truck? Can any of you confirm that for me?

Maybe that older style on there currently is less restrictive...with regards to air flow?

I have not used the truck yet to pull my 18ft enclosed toy hauler normally used in the summer heat with the A/C on. I bought this 6.5 last Oct. I'm just trying to assure I don't create any additional obstacles / restrictions with regards to cooling...for next summer while towing.

TIA 69

 

[ak diesel driver]

IIRC the 93 and older have 3 screws across the bottom of the grill and the bumper filler is pinned to the bottom of the grill with those plastic barbed push pins. 94 and newer the bumper filler is held on with screws and the grill clips to its. Personally I don't think the newer chevy grill would flow any more air might be diff with the gmc grilles though.

 

[Franko914]

<snip> Personally I don't think the newer chevy grill would flow any more air might be diff with the gmc grilles though.

I would tend to agree. Other than removing the front grilles completely, the air flow would remain unchanged.

It would be what's behind the radiator that would improve the air flow, i.e., the fan blades' ability to create a pressure differential that would dictate how fast air will flow through the radiator. If air flow out of the engine compartment is restricted, so would air flow through the radiator. Remove the restrictions and air flow will increase.

Sounds simple because it is simple.

 

[Detroit Dan]

I have a pretty stock setup, dual thermostats, can't remember what I put in when I changed them years ago, but I'm thinking about changing them to 180 ACDelcos. I am also thinking about doing the fan clutch mod. My problem is only when I'm either towing real heavy on the big hills or carrying the plow at anything over 50 mph. It gets up over 210 (factory gauge) seen as high as 230 and that scares me. Can usually hear the clutch fan kick on and bring it back down, but I have to take it real easy on the truck. I certainly can't just jump on the highway and run 65 with the plow on, it just won't do it.

Been wondering lately about fan clutch fan speed as it relates to engine rpm. The diesel runs at a really low rpm, so maybe it's not pulling enough air for the speed I'm travelling at. Was going to add an auxiliary electric fan but this thread has pretty much talked me out of that idea.

Funny thing is, all my old gasser plowtrucks I ran a clutch fan with an electric auxiliary fan, and they would heat up while plowing then cool off in between plowing jobs. This truck is the opposite, it heats up on the ten minute trips between jobs, then it cools back down while I'm working it hard plowing. I've added a homemade air deflector to my light tower to deflect air into the grille. It looks goofy but it works some, not as well as I'd hoped but it does make a difference. So it seems like my problems with airflow/cooling are not related to low speed poor airflow, but either from the blade blocking the airflow, or in the summer I guess the clutch fan isn't coming on soon enough and working hard enough.
I've pulled the radiator and thoroughly cleaned it, flushed it and added water wetter. There was absolutely no improvement with the water wetter, in fact it ran a little hotter on the first big trip after adding it.

 

[Detroit Dan]

Couple other things: Our grilles, on the Chevy anyway, are notoriously small. How much benefit could be gained by using a heat extractor hood? And would a simple cowl hood work this way? I'd put vents or a scoop on my hood if I had a clue what it was going to do.
Secondly, my AC compressor failed years ago and I replaced it, had it charged and it leaked down, after a couple tries I gave up on it. I honestly don't care about AC, never use it and wouldn't miss it if it were gone. Would I see a big benefit from pulling the AC condensor out? And if I did, should I toss the compressor too and go with an even shorter belt?

 

[NVW]

Couple other things: Our grilles, on the Chevy anyway, are notoriously small. How much benefit could be gained by using a heat extractor hood? And would a simple cowl hood work this way? I'd put vents or a scoop on my hood if I had a clue what it was going to do.
Secondly, my AC compressor failed years ago and I replaced it, had it charged and it leaked down, after a couple tries I gave up on it. I honestly don't care about AC, never use it and wouldn't miss it if it were gone. Would I see a big benefit from pulling the AC condensor out? And if I did, should I toss the compressor too and go with an even shorter belt?

I can't see how pulling one more restriction couldn't help, jmo.

 

[WarWagon]

I can't see how pulling one more restriction couldn't help, jmo.

Removing the condenser will help with less restriction and remove a cold metal "filter" that can plug up with snow. The radiator is the same snow filter but it is hot and will melt the snow.

Say going over the Rocky Mountains - Eisenhower pass 55 MPH in 4WD couldn't see the hood ornament blizzard conditions on the 6.2 Suburban and wondered why the engine was heating up. Stopped to let the engine cool and watched the water pour out the front as the radiator heat was able to warm the plugged condenser. Going slow allows the snow to melt - going fast doesn't... So may apply to your plowing - check the condenser sometime for snow buildup.

As to the plow question and fan clutch mod:
Matt Bachand has all the results you need here with his plow: http://www.thetruckstop.us/forum/showthread.php?t=12265 Can't :BDH: any better than was done there...

 

[Big T]

My '95 Suburban has always been missing the plastic deflection material behind the driver's side vent in the bumper. After my recent purchase of the '99 Surban I notice that it runs 5 to 10 degrees cooler and I'm wondering if that could be the difference?