Replace Idler, Tensioner or Both

[Alpinerunner]

I'm doing to replace the main drive belt on my 35D as I have a periodic squeak at startup and I'm at 100k miles. Does the tensioner or idler pulley usually fail/squeak? Or is it both? I'd rather not replace parts I don't need to on this car.

[smassey321]

For the diesel, a common failure in that area is the harmonic balancer. Get a mirror on a stick and inspect the front of it for cracks in the rubber. Another thread mentioned a potential recall but that is just an internet rumor at this point.