Engine Temperature

[hummerabia]

My '07 runs constantly up to the 3/4 mark during the Arabian summer however never gets any higher than that, and we are talking 48 degrees celcius ambient temp in town. Out in the desert it frequently tops about 55 celcius but very little relative humidity and so far have not experienced an AC shutdown owing to high engine temp.

Ran a test last year with my '06 H3 and a guy from GM in his H3 in a mad heat of 56 degrees all afternoon with the AC on with no overheating issues so I guess you can say they got it right with the cooling system.

[Matt19]

Originally Posted by hummerabia

Ran a test last year with my '06 H3 and a guy from GM in his H3 in a mad heat of 56 degrees all afternoon with the AC on with no overheating issues so I guess you can say they got it right with the cooling system.

lol 56degrees is cold! atleast it is to me

oops my mistake, your talking celsius

There's no guage reading on the Thermostat, so it is difficult to determine what the actual temperature is in the cooling system.
That said, the guage does show a very small red area at the top so it would appear to me, that anywhere but the red area would be a normal operating temperature.

When we were getting the hot humid blast of air, over the last two weeks, I was noticing my guage creeping up towards the 3/4 mark as well.
This was only while the vehicle was stopped.

Once on the move the radiator cooled things off relatively fast. the needle crept back down, and hovered just above the center.

Now with the cool weather the rain brought, everything is back to sitting in the middle.

[Stevenblanca]

Thanks everyone.

Some remarks:

1) Water is a better conductor of heat than coolant, Coolant raises the boiling point and lowers the freezing point and do some additional stuff like rust protection etc... The 30% to 70 % ratio I have is a trade off. My boiling point is lower (not very significantly according to the coolant specs) but the mixture absorbs the heat better.
2) I live on an island in the caribbean, no hummer dealers, no warranty. Can pretty much do whatever I please with my truck. Everything that happens to the truck comes out of my own pocket. (not much has happenen yet at 28000 M)
3) As you pickup speed, the temperature drops and the needle goes to the middle. This is because the heat is being blown off the radiator by the air rushing towards the truck (or the truck rushing through the air)

Remark 3 makes me believe that the stock fan speed is weak. When the truck is not moving it can not create enough airflow to cool the radiator properly. Just wanted to know if someone installed an el. fan. that obviously can move much more air than the stock fan, especially at idle or in slow moving traffic.


Again thanks guys.

[SR1355]

I run hot when on trail... I've noticed it seems to be a combination of fan CFM and water pump rate. If I sit at idle in 100 weather the gauge will creep upwards toward the red zone... If I run the engine at around 2K rpm, in neutral, the temp comes down. Does the fan run faster at higher RPM??? or is it constant RPM??? I know the water pump runs faster pushing more coolant thru radiator... It's never overheated but you can tell that it's damn hot. Wonder if higher CFM electric fan on other side of radiator would help...

[SR1355]

Something like these:

http://www.flex-a-lite.com/auto/html...-electric.html

[Stevenblanca]

Originally Posted by SR1355

I run hot when on trail... I've noticed it seems to be a combination of fan CFM and water pump rate. If I sit at idle in 100 weather the gauge will creep upwards toward the red zone... If I run the engine at around 2K rpm, in neutral, the temp comes down. Does the fan run faster at higher RPM??? or is it constant RPM??? I know the water pump runs faster pushing more coolant thru radiator... It's never overheated but you can tell that it's damn hot. Wonder if higher CFM electric fan on other side of radiator would help...

The fan does run faster at higher RPM, it is driven by the engine. Water is the best medium to transfer heat. Coolant is not. You can check this with any cooling system expert if you don't believe me. Coolant just raises boiling point, lowers freezing point, prevent deposits, prevents rust. It does not cool or transfer heat better than water and it does not make water transfer heat better.

Specific heat of water is 1.0. Meaning it takes 1 BTU to raise 1 pound of water 1° F and is assigned the 1.0 specific heat number.

50/50 mix of ethylene glycol (green coolant) has a pecific heat number of 0.5
50/50 mix of propylene glycol (red stuff) has a pecific heat number of 0.3

Pure water will remove double the amount of heat and carry that heat away from the source per unit volume compared to the 50/50 mix of the green stuff.

[usetosellhummer]

do not put green in a modern GM product or it will turn black. Dexcool only.
I run hot and on the trail the ac sometimes stops blowin cool. I am gonna get it checked. MY 06 never ran this hot, the service guy says 3.5 to 3.7 is why more heat. I don't buy it.

[Wisha Haddan H3]

Since switching to synthetic oil (mobil1), my engine temps are more stable. I was able to use the A/C crawling around hells revenge in moab last month and the needle stayed just above center.

And switch back to 50/50 coolant. At 70% water, you're not doing your engine any favors.

Coolant has 3 main jobs ... keep the liquid from freezing, keep it from boiling and help with heat transfer. Using the right ratio of coolant to water raises the boiling point and lowers the freezing point to the most extreme temps. And although water alone has a higher specific heat than coolant (it carries more heat per unit of volume), it transfers heat much slower. A 50/50 mixture creates the right balance between the amount of heat carried and the rate it can be carried away.

Some people swear by water-wetters to reduce engine temps. I have no experience with them, but maybe others will chime in.