Random coolant leak?

[rich4130]

Hi all, bit of an odd one, had a couple of instances of my coolant just totally disappearing! I think it's a leak rather than anything serious, any ideas? S3 8l! Have replaced the exp tank cap btw!

[Powelly]

Any visible leaks? Check any joins, Look for splits and check the thermostat housing If not try the sniff test, Stick your nose in the expansion tank and see if it smells of exhaust fumes, Is there any excessive white smoke coming from the exhaust?