As the title says really, on very cold starts such as this week there is a faint grinding noise coming from my engine bay. If i pop the bonnet it can barely be heard above the normal engine noise but inside the cab its very noticable. I cant really pinpoint where the noise is coming from because its so faint but at a guess i'd say to the right side of the engine bay (airbox side). The car hasnt had anything new done to it other than oil/plugs 2 weeks ago and the noise just started one morning. Ive had a quick google and cant find anything that sounds similar to my problem so i thaught i'd ask. When i replaced the drive belt i did notice the tensioner pulley was a bit loose but they make a high-pitched squeal rather than a low pulsating grinding noise. The noise does knock off when the engines warmed up a bit and i have noticed that the fan comes on as soon as the engine does. My best guess is that water has frozen inside the radiator and the pump is sucking on nothing and triggering the cooling fan because its not registering any differance in coolant temperature, sound reasonable? EDIT: warranty runs out next week so if it sounds serious i'd rather get it done sooner rather than later.