I recently had to deal with a squeaking noise under the hood of my car. Initially, I felt certain the fan belt tensioner was shot, but after a cursory look under the hood, I realized I couldn’t be sure. So, rather than simply asking my dealer for a quote to replace the tensioner, I took a different path — I asked her to run diagnostics and do a complete under-the-hood inspection. My initial diagnosis was wrong. The inspection revealed that the tensioner was fine, but the harmonic balancer was the issue and, by the way, my water pump was beginning to leak and needed to be replaced soon. And, since they would have the radiator out to fix the harmonic balancer, I could save labor costs by addressing the water pump issue now rather than later.