Strange horn noise

[Gavlar2021]

When I turn the engine off above the radiator is a small unit with three pipes two rubber one metal it go's tick tick tick then it sounds like a ships horn sort ov noise

[Vauxhall Owners Club]

Sounds like it could be a PCV valve or similar which is releasing pressure or resetting.

If it is making that sort of noise then if one of the lines is running pressure or vacuum and is split then it can create this noise

Carefully examine the hoses going to the unit