Engine Tune-Up and Break-In
PRELIMINARY ENGINE TESTING
bubbles. Either condition would indicate problems
Before tuning-up an engine, determine if a tune-up will
which require engine repairs rather than just a
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
3. Perform a dynamometer test and record power
only those necessary to restore the unit.
output. (See DYNAMOMETER TEST later in this
group.) Repeat dynamometer test after tune-up.
1. After engine has stopped for several hours, loosen
Compare power output before and after tune-up.
crankcase drain plug and watch for any water to
seep out. A few drops could be due to
4. Perform compression test (See TEST ENGINE
COMPRESSION PRESSURE in Group 105).
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