Living here in the PNW/Washington state. Last month or so on my 13 O.B. 2.5, parked inside unheated garage or outside with night temps in the low 30's or high 20's, when I first start the car, there is a very "slight knock" for a split second on start up. Car has 29k miles on it, always serviced on time, last serviced at dealership, oil change etc. fluid levels all up to full. Only knocks for split second and only when dead cold. Any advice from anyone on 13 or similar year 2.5?