Refilling Your Cooling System

[misterp]

After installing the 5.3L in Dan's S-10 pickup we filled the radiator as described in my How-To on changing your thermostat, filling the radiator and coolant puke tank. After starting the motor it overheated in just over a minute, and the thermostat stubbornly refused to open. Dan and I looked at each other and agreed that there was most likely an air pocket on the back-side of the thermostat preventing it from heating and opening. We let the motor sit and heat-soak, and started it again to encourage the thermostat to open and again the motor overheated; the thermostat never opened, the cooling system still had air in it and was refusing to "burp".

 

The solution was to remove the upper radiator hose from the radiator, and pour coolant into hose so it would enter the engine 'backwards' through the upper neck of the water pump; doing this I was alarmed after I poured in the THIRD GALLON of coolant into the upper hose! Apparently we filled the radiator using the traditionally accepted method, but the cold/shut thermostat did not even let any coolant leak into the motor, the block and heads were bone-dry and most importantly the water pump was dry hence not primed and not moving coolant.

 

So the lesson I learned is, on LS-motors when you drain the entire cooling system (below the level of the thermostat) you need to fill the radiator (like normal) and then ALSO refill the motor through the upper radiator hose, then connect the hose to the radiator and start the engine.

 

Mr. P.

 

PS - FYI, the dry/total capacity of the cooling system on a LS-motor is right at 4-gallons.

Edited May 19, 2009 by Mr. P. (see edit history)

[JF-03-SS]

Good info to know, thanks for sharing.

[Badkarma]

makes sence on a dry motor. I used to fill new small blocks thru the maniforld when they were dry so y our method makes sence about the air pockets

[shakesvho]

good stuff, thanks for the info

[ss wrecker]

this must have been what was going on when we did the cam swap on my truck. thermostat wouldn't open until dan completly took the hose off

[Jaymz]

<------ "writing this down"

[Posi12Bolt]

using that thought process my escalade is still 2 gallons low...

 

good thing I haven't let it get to operating temp yet with the new engine

[mcmahan]

thanks for the info steve