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 8-27
Also, water used as a coolant for even a relatively short
period can result in the cup plugs rusting through, allowing
the coolant to leak.
NOTE: A sudden loss of coolant from a heavily loaded
engine can result in severe damage to the pistons and
cylinder bore.
An incorrect or malfunctioning cap can result in the loss of
coolant and the engine running hot. Refer to Procedure
008-047.
Air in the coolant can result in loss of coolant from the
overflow when the aerated coolant is hot. The heated air
expands, increasing the pressure in the system, causing
the cap to open.
Similarly, coolant can be displaced through the overflow if
the head gasket leaks compression gases to the coolant
system.
The operating pressure of the coolant system and the lu-
bricating system can result in the mixing of the fluids if
there is a leak between the systems: head gasket, oil cooler,
etc. (refer to the Lubricating Oil System - Section 7).
NOTE: Transmission fluid can also leak into the coolant
through radiator bottom tank transmission oil coolers. Re-
fer to the OEM service manual.
L-1083
