If this is on your '98, The tensioner pulley contains a large spring for tensioning, instead of the troublesome rubber-sandwiched tensioner pulley mechanisms found on earlier engines (M102, 103, 104). Rarely see the mechanical spring tensioner assembly go out, but they are a very simple and uncomplicated replacement, compared to the sometimes nightmarish jobs that tensioner replacement of yesteryear required. You should not have to replace the entire tensioner assembly, just the pulley (very common), but it is easy enough to replace if you want to.

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