i have a 2005 bmw 325i and it has a growling noise from motor only on occasions one minute it is fine the next it growls any advice

What is your question?

this just started yesterday it was real cold outside, also I have a new radiator to install. Have completely tuned up car and fixed all hoses and sensors,still runs like a champ just now a growl has started. It is not all the time but need to figure this out Thanks

How long has your 2005 BMW 325i had this problem?

2 days