[Speedwaypj]

thx for the info - cycleguy55
I was only using the 21# because it was getting to 18psi (w/o expansion tank) and the 16# and 18# wouldn't hold...it would push out coolant thus causing overheating. Now with the 2qt expansion tank there is more (air) volume so the pressure is not high now. I plan to go back the 16# and adjust coolant level.