1999 Cadillac Catera 6 cyl Two Wheel Drive Automatic 120000 miles. We are replacing the head gaskets on our '99 Catera. What is the importance of replacing the serpentine and timing belt tentioners within the same process?
Maybe they are fine today and next week they aren't. The more critical one is the timing belt one as it is more labor intensive to go back into. The serpentine belt tensioner is more accessible and will give some warning signs of going bad. If it was mine I would do the timing belt tensioner because I'm there, serpentine tensoner. If it is moving free and was not cocked when mounted, you could reuse it.