coolant reservoir/upper radiator level

[tmontague]

I recently flushed and filled my coolant following CT's guide which drain's the block, 'rad and the overfill reservoir. I also replaced the t-stat, gasket and radiator cap.

It's now been a week since I have topped it back up and every evening I have been topping up the radiator after the engine cools since I drive about 90km round trip out to school and back. The topping up is expected due to air being brought to the surface.

I will top the 'rad up with about 1/6 a cup of coolant and then drive for a while. When it cools the coolant is no longer at the top of the cap, it is only seen when the top 'rad hose is squeezed. I figured by now the air should all be out of the system.

The other day I noticed that the coolant level dropped a little as usual at the top of the 'rad but the overfill reservoir level increase about that same amount that was lost.

My question is this: Why is the coolant not being pulled form the reservoir back to the top of the 'rad cap when it cools? I understand that this will not cause any engine problems but it should be topping up to the cap.

I have checked for leaks and water pump issues and there are none, everything is working fine with the cooling/heating system and there are no leaks what so ever.

My theory is that there is air in the line going from the bottom of the reservoir up to the rad cap opening. I am going to try pushing the air out of the line and see if this stops the issue. It seems that the system is not loosing any coolant but it is not fully being pulled from the reservoir back into the top of the rad when the coolant cools.

If anyone has any experience solving this annoyance please let me know.