I just installed a 180 T-stat, and don't seem able to get all the air out of the system. I fire it up cold with the radiator cap off, idle it for 20 minutes, run the tach up to 3500 Rs, and the fluid level only drops enough to put about a shot glass of coolant in it. Anytime I run it above 2800 RPM, the gauge drops off into the cold zone. Let the RPM drop below 2500, gauge comes back up to 1/3. After several test runs, each time letting it cool for 3 hours or so, I check the coolant reservoir level, and it doesn't look like the engine is sucking coolant out of it, as the level doesn't appear to change. I'm scared to death of barbequeing this thing. I even tried warming it up with the front end on ramps, but it didn't help. Oh, yeah - I did all this with theater running, and it does blow heat.

 

1. Make sure your radiator cap is functioning properly or just buy a new one.
2. Ensure the hose between the radiator and overflow bottle isn’t plugged.
3. For the system to equalize you must let it sit overnight. May require several days to purge all air.

If the above does not work or you’re concerned try the following:

First thing in the morning pull the radiator cap and top off. Find the steepest grade available (20-30 degrees). Position the front of the truck up. Run the engine at 2500 rpm until the thermostat opens. Alternate rpm to 4000 for 5 seconds and return to 2500. Do this several times. Lower truck and drive around at varying road speed for 10-15 minutes.
Allow engine to completely cool, preferably overnight. Next morning check the radiator and overflow bottle level. Top off as needed and repeat above as necessary.

Another method I’ve found that helps is to install a coolant flush T in the heater core return hose. When filling the radiator I normally leave the T open and fill until coolant comes out the T. Let it settle and repeat. If the coolant overflows the radiator before coming out the T, install the radiator cap and then back fill coolant through the T until full. Cap off the T, and start the engine and alternate rpm between idle and 2500 for 30 seconds, idle for 30 seconds, alternate rpm for another 30 seconds. Turn off engine and slowly open the radiator cap. Check level and top off as needed. Continue to check overflow for several days.