Coolant loss

[Allan mason]

Loosing coolant when under load over a long distance, ie towing a caravan. All other times solo it is ok. The radiator and expansion tank cap have been replaced with genuine Volvo parts. The system has been pressure tested. The low coolant alarm alerts after about 400 miles. Looking at the expansion tank the level is at LOW. After the engine cools and I release the pressure and the level comes back to normal-ish. I have to put a small amount of coolant in. Any bright ideas. I am stumped.

 

[Norriarty]

Hi Allan I have exactly the same issue with my xc60 D4 AWD, had it pressure tested, nothing, changed header tank cap, still leaks. Bought a sniffer test kit to check if there are any engine gasses in coolant which might indicate a crack somewhere, negative. Sorry but I haven't got an answer yet. Must be other people out there with the same issue?!