Coolant

[Jonty]

Hi all

I’ve posted re this before but have more info. My coolant is bubbling like a bubble bath. It will start small bubbling when cold and also foaming and when hot it will look like a kids bubble bath in the reservoir.

The standard response and my initial reaction was head gasket. However it has never overheated (and doesn’t over heat now) and I have had a mechanic run the gas analyser test, a compression test and a full leak down test. It passed them all with flying colours and everyone is baffled.

There are no coolant leaks I can see anywhere and it’s not losing coolant.

Would anyone have any ideas? Also could a head gasket be gone if it’s passed all those tests?