Answer:
Both Technicians A and B
Explanation:
You can do paper towel test to detect if your intake or exhaust valve is burnt. To carry out paper test, place a piece/single sheet of paper over the tips of exhaust pipe while the engine is running. If the paper seems to get sucked back into the pipe, there is a chance you have a burnt exhaust valve. Therefore, Technician A is right to say that the paper test could detect a burned valve.
For Technician B; When looking for coolant leakage in the cooling system, check for rusty or grayish- white stains. Rusty or grayish- white stains serves as a leak indicator in the cooling system. If you don't find an external leak, you'll need to run other tests to uncover the leakage. Therefore, Technician B is right to say that a grayish white stain could be a coolant leak.
