Why is the coolant 'high and low' so close together on the Auris?

[Mike 2121]

Just got told mechanic had to top up coolant alittle on service and to check it again in a few days. If it's not a leak what else could it be as car drives smooth and perfect?

[Bper]

Hi Mike, if there are no visible leaks from hoses etc it is possible that the water pump could be failing . How much coolant had been lost and is this the first time.

[Mooly]

The level will probably alter a little with temperature, a hot engine giving a higher level. If it was checked cool or only warm it may have been on the minimum mark which fine. Get the engine really hot and it will be closer the max level.

[TonyHSD]

Coolant can evaporate when the car is driven in hot days. Normal to top up a bit. Why its the difference between full and min level so small I don’t know. It’s like 200ml and this is what I topped up for the entire summer 20k miles , and it was scorching hot, remember🥵

[furtula]

Coolant level is measured/topped up when the car is cold.

[Mike 2121]

 Cheers guys. Not sure how much he needed too top up

[Trewithy]

It's best to check the coolant when the engine is cold.  This will give a better indication of any coolant loss.   If checked when hot it will have expanded due to the heat and the amount of expansion will depend on engine temperature and the length of time the engine has been running and you are liable to see different levels each time it is checked.  For consistency and comparisons of readings check when cold, first thing in the morning would be good. 

[AisinW]

Most older cars need top up the coolant annually. Some of the water evaporate from the ventilated reservoirs.  I usually only add distilled water because the antifreeze remain the same. 

In 3rd gen Hybrid, the radiator and reservoir cap are the same and I never need to top up after almost 7 years. I believe the ventilation is open only if the pressure is too high but hybrid engine is very stable even with constant climbing or 130 kmplh cruise in autobahn.