Coolant flow rate?

[LegoHead]

I have refilled the coolant system and wonder why there is only a small trickle of water back into the header tank when the engine is running? Is this normal?

Also, the level was going up and overflowed when I switched engine off, then dropped back down after a little while. What causes this?

Cheers.

 

[BenR]

All is normal.

pressure differential across the pump, boiling point changes with cap off, and all effects system pressure hence the overflow when you shutdown.