My 1990 Honda Civic is making a whining / squealing noise from the timing belt. I pulled the cover off thinking it might be rubbing against it but that was not the problem.

Anyone know what would cause the timing belt to do this? I have not had it long and it was doing this when I bought it so I don't know if it has been replaced. A shop wants to check it out.

If it is the tensioner what will that cost to fix?