Hi, thankyou for the reply . Yeah the bottom pipe stays cold until around 78c like I’ve said , so you think it might be ok? I did a flush on it this weekend but it’s made no difference. MAybe I’m just overthinking it ?only reason I checked was I had intermittent cold air in the heaters but I topped the coolant up and it’s been fine . How could I go about trying to get air out of the system ?