A borescope is used to inspect internal parts on an engine without having to disassemble the engine. This instrument helps a great deal in estimating the amount of repair work needed and the time required for the repair. Figure 2-9 shows a typical borescope.

Figure 2-8.Locations for taking crankshaft deflection readings.

Most borescopes have the following basic components:

1. Eyepiece (zoom or wide angle)

2. Scan control ring

3. Probe tube

4. Scan mirror

5. Quartz-lined lamp

6. Focus control ring

7. Other electrical accessories

As with any optical instrument, you should handle the borescope with care to avoid damaging its lenses and mirrors. The borescope is powered by alternating current. So, before you first use it, be sure to read and follow the manufacturers operating instructions. The borescope can be inserted through any engine opening, such as a cylinder port, to identify problems, such as cracked pistons, cracks in the cylinder head, burned valves, and scuffed or pitted liners. You can remove the crankcase cover to inspect the bottom section of the engine.