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The typical cost to replace a timing belt in your vehicle is about 5 hours of labor. Depending on the labor charge where the work is being done. Average labor charge for dealerships is 95 dollars per hour and average for independant shops is 70 dollars per hour.
To replace the Mass air flow sensor I would say you'll be charged about an hour.
Neither the Mass air flow nor the timing belt will cause overheating.
For a diagnostic test to see why your vehicle is overheating usually dealerships will charge 1 hour diagnosis time and independant shops will charge half an hour.
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