OK HOW LONG DOES IT USUALLY TAKE TO GET ALL THE AIR OUT OF THE COOLING SYSTEM?

I have topped it off I think twice now.. it was only a little below the neck both times.. so the last time I put a little over the cold line in the overflow and it's gone down just a little but I haven't driven it since.. I just had it running for about 15 minutes.. is it harder to get the air out if the thermostat never opens?? I never had it above 135F and the thermostat is a robertshaw 180 which is drilled.. so of course it's always flowing somewhat.. I don't seem to have any leaks either..

 

When you fill any closed container with fresh water, the air that is entrapped in the water will eventually liberate and create a bubble. Your container is your cooling system, and even though the water was mixed with coolant, it still contains air molecules. The water will eventually deaerate, but it will occur faster if the water is heated above 180°F. You may have to heat the water for several hours to drive off all air.

In a closed system that builds pressure, the process will take even longer since the air cannot break free of the water as easily. You can either heat the system with the radiator cap off or loose for an extended time, or allow the engine to go through normal heat/cool cycles for several days and keep the system full. Eventually, the air will be dispelled and the system will maintain level.

It takes the better part of a week on an LT1, since they are prone to having pockets of air in the cooling system.

This isn't only an automotive phenomenon. It happens in any closed hot water system. Most medium and larger boiler installations have a separate feeder tank that is preheated to 180°F or above to deaerate the water, and sometimes chemical additives are used to dispel the air before the water is even pumped into the boiler itself. An air bubble in a high pressure boiler can be a very bad thing.

 

you can pick up a coolant system funnel from many parts suppliers. I know Matco makes a nice kit for about 11 bucks or you can just make something to work. The funnel fits on the radiator and seals off to the neck so that the overflow hose is not open. If you can find a funnel that will press into the radiator and seal in the neck, that will work fine. Your objective is to get antifreeze above the level of the engine or the highest point there is coolant. LT1's are very tough as stated and this system works great. Install the funnel and fill it with coolant/water and allow the engine to run as long as it takes. It will usually open the thermostat and bubble a lot and possibly suck the coolant in the funnel into the motor so be ready for a refill. It may boil over a time or two but don't worry, just rinse everything off afterwards. It usually takes about 2 or 3 thermostat "cycles" to get it full and it should sit there and run without many big bubbles coming out of the funnel. Next, remove the funnel while it's running and install the cap. Give the overflow a good supply of mixture and rinse everything down. Antifreeze is corrosive to paint over time so don't let it sit for weeks or anything.