TM 5-2420-230-24-2
B3.9 and B5.9 Series Engines
Cooling System Diagnostics (008-020)
Section 8 - Cooling System - Group 08
Page 8-25
A positive result from the combustion gas leak tester in-
dicates the following:
Cylinder liner protrusion incorrect. Refer to the B
Series Shop Manual, Bulletin No. 3666017
Cylinder head gasket or cylinder head casting leak-
age. Refer to Procedure 002-004
Injector sleeve leakage. Refer to Procedure 002-004
NOTE: Discard the test fluid if it has indicated positive.
A negative result from the combustion gas leak tester,
coupled with continuous flow of air bubbles from the pre-
vious test, indicates the following:
Defective fan, shutter, or heater air control valve
Air compressor head or head gasket leakage
Air entrained due to a bad radiator check valve or
incorrect fill.
Cooling System Diagnostics (008-020)
General Information
When you troubleshoot overheating, remember that too
much oil in the oil pan can cause additional heat from
friction when the rod journals are submerged in oil.
Overfilling with oil raises the oil temperature that is trans-
ferred to the coolant system at the oil cooler.
The system is designed to use a specific quantity of cool-
ant. If the coolant level is low, the engine will run hot.
NOTE: The engine or system has a leak if frequent addition
of coolant is necessary. Find and repair the leak.
L-1081