Engine Rebuild, Break-In, and Tune-Up
PRELIMINARY ENGINE TESTING BEFORE
Before tuning-up an engine, determine if a tune-up will
restore operating efficiency. If in doubt, the following
preliminary tests will help determine if the engine can be
tuned-up. Choose from the following procedures only
those necessary to restore the unit.
1. After engine has stopped for several hours, loosen
crankcase drain plug and watch for any water to seep
any more than this would indicate problems which
require engine repairs rather than just a tune-up.
2. With engine stopped, inspect engine coolant for oil film.
With engine running, inspect coolant for air bubbles.
Either condition would indicate problems which require
engine repairs rather than just a tune-up.
3. Perform a dynamometer test and record power output.
(See DYNAMOMETER TEST later in this group.)
Repeat dynamometer test after tune-up. Compare
power output before and after tune-up.
4. Perform compression test (See TEST ENGINE
COMPRESSION PRESSURE in Group 105 of