5.3 overheats when going up mountains. Any ideas?

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20Grand

Apprentice
Mar 16, 2018
59
10
8
I’ll lose almost 1.5 gallons of coolant when going up mountains. I have a 5.3, 4l60e with stock v6 gears. I think 273s or something like that. Anyways, any ideas? Could it be that my rear end is pulling my motor abdctrans down? I have a 1k treck back home and I’d like to make it.
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
2,067
3,053
113
mpls
If its only overheating when at altitude, I'd check your radiator cap. Make sure its keeping the correct pressure in the cooling system.
Also, is your coolant the proper mixture. 50/50 antifreeze to water is the easiest to install. Remember, antifreeze is also an anti-boil liquid.
Science class time, everything boils at a lower temp the higher up you go. Water boils at 212f at sea level but drops to about 200f at 5000 ft. Or something like that. Same idea applies to coolant.
 
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UNGN

Comic Book Super Hero
Sep 6, 2016
3,048
3,264
113
Southlake, TX
Do you have a radiator support air dam? What is your thermostat? Does it have electric fans?

I doubt it was the 2.73 gears. Even if it was, you could always put it in D to take the load off.
 

motorheadmike

Geezer
Nov 18, 2009
8,976
27,522
113
Saskatchewan, Truckistan
That coolant had to go somewhere: either into the combustion chamber or out onto the road.

Time to pressurize the system and see.
 
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Reactions: 1 users
Oct 14, 2008
8,806
7,746
113
Melville,Saskatchewan
What temp are you reaching? Tell us everything, rad, fan, shroud, air dams, coolant mix, thermostat etc.
 

20Grand

Apprentice
Mar 16, 2018
59
10
8
If its only overheating when at altitude, I'd check your radiator cap. Make sure its keeping the correct pressure in the cooling system.
Also, is your coolant the proper mixture. 50/50 antifreeze to water is the easiest to install. Remember, antifreeze is also an anti-boil liquid.
Science class time, everything boils at a lower temp the higher up you go. Water boils at 212f at sea level but drops to about 200f at 5000 ft. Or something like that. Same idea applies to coolant.
Brand new cap but I can go pressure test it once more. How important is the overflow tank? The threads melted when it overheated on the way over here. Also, I’m running 16lbs, that sound about right? I’ll drain and mix with 50/50 before heading out.
 

Texas82GP

Just-a-worm
Apr 3, 2015
7,981
18,676
113
Spring, Texas
Do you have a high stall speed torque converter? You might need an auxiliary trans cooler.
 
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