I can tailor my answer better if I know why the tensioner has been recommended. What symptoms or problems are you having? Also, when talking about engine parts, I really need to know which engine you have. You listed a V-6, so am I right in assuming it's the 3.8L?
The tensioner is rarely replaced on its own. Typically the timing belt breaks or is being replaced for maintenance. THAT'S when the tensioner and water pump are replaced. That's to insure the quality of the repair. The 3.8L is an "interference" engine. When the timing belt breaks, the engine stops running and you need a tow truck. With an interference engine, any open valves get hit and bent by the pistons as they coast to a stop. That turns a maintenance repair into a very expensive valve job.
Worn bearings in the water pump or tensioner pulley, or a weak tensioner can allow the timing belt to shred on the sides or jump a few teeth on a sprocket. No reputable mechanic is going to replace just the belt without also replacing the water pump, tensioner, and pulley. Saving those few dollars is very short-sighted and not in the car owner's best interest. The cost of those additional parts is very small compared to the cost of a valve job, and it is cheap insurance. I would not have much respect for a mechanic who offered to replace just the timing belt on an interference engine.
Saturday, February 8th, 2014 AT 6:11 PM