Coolant level

[st.tony]

Yesterday my 2019 cupra st flashed up a coolant level warning, 3 times in fact, everything looks fine tho.

This morning no issues but again just as I got home this afternoon it flashed up again.

Looking at it it was under minimum until I unscrewed the cap where it jumped up to max, is this typical as I can't say I've noticed before.

Searching on here it seems it's possible that it may have a common fault that I had on a fabia vrs I had a few years ago where I ended up needing a new coolant tank (faulty sender), IL get it looked at regardless however the manual states don't drive it but as I say everything "seems" to look ok.

Anyone got any suggestions?

 

[RUM4MO]

Tricky one maybe, but, if the level is being pushed down when this happens with a hot engine, I'd no think that it is the old sensor failing issue, but something else causing the tank to get pressurised - maybe cylinder head gasket failure or just air trapped in the system, but if the cooling system has not been opened up recently and this pressurising is a new event, I'd think that you need to get it checked out.

Over many years I have run cars and none of them ends up with its cooling system level moving much from cold even down to -10C and when the engine is hot even in summer temperatures.

 

[Copra68]

Only check the level when the engine is cold and hasn't been run. If you open the cap when it's hot you'll get a false reading and possibly scald yourself if the boiling coolant spews out.

 

[RUM4MO]

Only check the level when the engine is cold and hasn't been run. If you open the cap when it's hot you'll get a false reading and possibly scald yourself if the boiling coolant spews out.

I agree with all that, but it is also good to check coolant level when the engine is running and or just after a hot run to give yourself a better understanding of what is happening and what to expect if checking it in the future - I'd never loosen the cap when the coolant is hot, that is asking for injury certainly. unless you fully understand what might happen and take precautions.

 

[andycupra]

sounds like you removed the cap when it was not cold.
if so you need to take the cap off and leave it off until it is cold, but as said opening when hot can be dangerous,
if it was hot when you removed the cap, then the system was pressurised, pipes etc have expanded, when you removed the cap these relaxed and voila the level increased.

When the car it not hot, take the cap off, leave it off, run it for a bit to get up to temp, then leave cap off and let it cool down properly. check the level, and if required top up so its in the range but in the lower half would be my advice.

Often this time of year it is simply due to the lower ambient temperatures, coolant when cold will be lower as the ambient temps are lower.