coolant msg

[padjoe]

today i got a coolant low please stop msg on dash
so found somewhere to pull in and reversed into space as i was doin so the warning went off--
checkd the coolant and it was below the min
so i slowly opened the cap as the engine was toasty and a large sqeual and hiss but then the bottle filled back up
this is the first time ive seen this dont really know what to make of it
should i be worried, is this a sympton of something

[sneakypenguin]

Best thing to do is check the level when the engine is cold, it's a pressurised system so it maybe under the min when hot but above min when cold, I generally keep it up to the max line. I wouldn't be worried tbh, just keep an eye on it as part of the weekly check

[padjoe]

i thought coolant should rise a little when hot thats generally why it should be filled just above mid way between min and max on bottle
the amount that it is being sucked in is what baffles me --from max to below min and then when pressure is released, the bottle fills back up to what seems like the same spot

[mikealder]

Check the level with the engine cold and top it up while its cold to the max mark then fit the cap, there is still an air gap above the fluid which allows for expansion, checking coolant levels with a hot engine at best will give you the wrong level at worst you will get scolded from escaping steam/ boiling water - Mike