I especially did not like the coolant pressure dropping to zero when reducing power and descending. I feel blind in this condition.  This is what you see when there is zero air in the system.  I like the Moroso expansion tanks because they can function as both air/coolant separator and gives room for the air spring volume.   

I added a Shrader valve to my pressure bottle. I pressurize the system to the valve pressure before I start the engine. So, the coolant pressure stays at relief valve pressure for the whole race. W#hen cold the pressure stays at 5 PSI. Used to hold it for a week. Now just overnight.

 

The bleeder hose should have a small ID, so as to move air bubbles quickly with small changes in heat load.

 

Lynn E. Hanover