Timing belts need to be replaced at regular intervals to prevent them from wearing out and failing. At my Honda dealership, we recommend replacing them at 100,000 miles. We also replace the water pump, and often replace the tensioner. Over time, the belt tensioner could start to fail, and if the belt is allowed to go too slack, it can jump timing and damage the engine.
A failing timing belt tensioner is usually diagnosed by a knocking noise from the tensioner with the engine running. This car was overdue for its timing belt by almost 30,000 miles, so it’s not surprising that the tensioner had begun to fail. In this case, it was leaking a lot of oil. I sold a timing belt job and began digging into it, but then found another problem.
The tensioner is a small oil-filled piston that pushes against an arm attached to a pulley that the belt rides on. On this car, the tensioner piston and the arm had gotten very worn, leading to the pulley arm needing replacing as well. In this picture you can see the worn area on the part on the left, and the new part on the right. After picking one up from another dealer, I was able to finish the job.
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