I tend to do the tensioner and idler when I do a belt. Last weekend I was trying to sneak out the factory fan on my Mustang to change it out with a 13-14 GT-500 fan without opening the cooling system. Unfortunately I touched the T connector off the t-stat and it started dropping coolant, then I looked at the water pump and saw the weep hole had some orange buildup. I had all the parts on hand because the car was at 62K and change and that is about when we do a lot of the Coyote water pumps. While I had it apart, I also put on the kit to change out the A/C stretch belt to a standard belt. If I was smart I would have spent more time cleaning up whatever buildup was near the timing cover, but I didn't want to spend more time than necessary. I used Ford / Motorcraft parts for everything except the coolant. I didn't have any of the new yellow on hand, and I didn't feel like going to work to get it. So I used some Dex-Cool I had for my truck.