I disagree, the tensioner should always hold pressure if it does not replace it. Temps here in CO are in the low single digits and my tensioner never does that. No matter how cold the tensioner must maintain pressure. The sound is chain slap. If the rails and chain are okay and the timing is not to far off then just put in a new tensioner. Your call, but fix the chain slap it will also increase wear on the chain guides.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)