5.3 overheats when going up mountains. Any ideas?

20Grand

20Grand

Apprentice
Mar 16, 2018
59
10
8
#1
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.
 
O

oldsmobile joe

G-Body Guru
Nov 12, 2015
830
522
93
mpls
#2
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.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
23,480
4,222
113
Kitchener, Ontario
#4
Is it overheating or are you just losing coolant?
 
Last edited:
Turbolq4

Turbolq4

G-Body Guru
Sep 25, 2017
818
754
93
Boise Idaho
#5
Do you have the steam line from the heads hooked up?

Do you have an overflow tank?
 
motorheadmike

motorheadmike

Comic Book Super Hero
Nov 18, 2009
2,758
2,874
113
Ottawa, Ontario Canada
#6
That coolant had to go somewhere: either into the combustion chamber or out onto the road.

Time to pressurize the system and see.
 
olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
3,439
817
113
Melville,Saskatchewan
#7
What temp are you reaching? Tell us everything, rad, fan, shroud, air dams, coolant mix, thermostat etc.
 
20Grand

20Grand

Apprentice
Mar 16, 2018
59
10
8
#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

Texas82GP

Comic Book Super Hero
Supporting Member
Apr 3, 2015
4,354
3,528
113
Spring, Texas
#9
Do you have a high stall speed torque converter? You might need an auxiliary trans cooler.
 

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot Mike's Montes P-S-T Southside Machine Performance UMI Performance

contact [email protected] for info on becoming a sponsor