Sniff test?

[itchyfeet]

When the head seals go on a WBX usual advice is a sniff test.

My question is how long do exhaust gasses stay in the coolant?

Do you have to do the sniff test while it's leaking?

If it only leaks hot will the gasses be gone by the next day when you start it cold?

thanks

[Mocki]

Well I have always thought of it like picturing lemonade in a glass, while the engine is running the gasses are little bubbles in the coolant , but when the engine is off they all rise to the highest point they can ( top of rad I guess) and join to make a bigger air pocket . So they are still there , and once the engine runs again, they get whisked around and break up into smaller bubbles again ,once the stat has opened , plus new gasses from the engine running
But that’s not water jacket seals , they only allow coolant out into the big wide world and suck air in when it’s cooling

[bigherb]

Sniffer tests are done with the engine running and from cold up to temperature, it is not unknown particularly with Diesels for head gaskets to only leak in the warm up phase.