question regarding coolant level, cold vs hot engine

[arron1995]

when i picked my car up the coolant level was on max, this was with a cold engine i believe, after work today i noticed my coolant level was just above the min line, the surface was flat, i went and got some coolant, got home turned the car off and wallah, coolant level was max... now i know how coolant works, it expands as it heats up, but never thought it would expand from the min to max line, is this normal? i thought you topped coolant to the max line when its cold, im wondering if it expanded and went over the overflow and this is why its dropped.

 

no sign of a leak anywhere.

[cliffcoggin]

There is air in the system. (Air expands and contracts.) Does the heater work?

[arron1995]

2 minutes ago, cliffcoggin said:

There is air in the system. (Air expands and contracts.) Does the heater work?

Yeah the heaters work.

[cliffcoggin]

Nevertheless I still suspect air in the system. Has it been opened or disturbed recently?

[Magnet]

Hello Arron,

My procedure:-

Assess the coolant level when cold - ideally when left to stand overnight. Top up to the max. mark. 
Use the car and inspect the level the following morning when cold. 
Should still be at the same level.

Kind regards,

Gareth.