What kind and size of bolt head holds on the belt tensioner for a 2002 Ford Taurus SE vulcan -hex or torx?

The belt tensioner bolt on a 2002 Ford Taurus SE with the Vulcan engine is almost certainly a hex bolt. It's unlikely to be a Torx. The exact size (e.g., 13mm, 15mm) will vary slightly depending on the specific tensioner and manufacturer, but it will likely fall within the 13mm-15mm range.

To be absolutely certain:

1. Consult a repair manual: A Haynes or Chilton manual specific to your year and model will have the exact specifications, including bolt size and type.

2. Check a parts diagram: Online auto parts stores (like AutoZone, Advance Auto Parts, etc.) usually have parts diagrams. Find the belt tensioner and its parts. The diagram may show the bolt size.

3. Look at the bolt itself: If you can safely access the bolt without removing the tensioner completely, you can see the size and head type. Use a socket or wrench to test different sizes until you find the right fit. Be careful; don't force anything.

Remember safety first! If you're not comfortable working on your car, take it to a mechanic.