Toyota Repair: 2000 Toyota Corolla Serpentine Belt, shock absorber, serpentine belt

Question
I want to remove the belt and check to hear if the noise at cold start is due to the belt tensionser. My problem, I can't get a wrench or socket on the nut/bolt for the idler pulley (tensioner). I tried 12-pt. 13 mm and 14 mm socket
and combination wrench. I also tried 6-pt. 13 and 14 mm socket and none seem to fit properly. Does this require a special tool? If so, what and where can I get one. Do you have any advice on cold start noise that goes away after engine is hot? I have been advised by a Toyota mechanic to check the belt tensioner and the timing change tensionser that I believe is driven by oil pressure.  Thank
YOu."


Answer
The noise is coming from the belt tensioner and I believe toyota had issued a service bulletin a few years ago, the tensioner assembly and the belt need to be replaced, the tensioner comes as a complete assembly including the bracket, the pulley and what looks like a small shock absorber, there is only one large bolt(17MM) that holds the assembly on, there is a 19mm protrusion, with a 19mm socket and a bar move the tensioner to release the tension to get the belt off.