The system is designed to use a pressure cap to prevent boiling of the coolant.
Different caps are specified for the two recommended systems:
An incorrect or malfunctioning cap can result in the loss of coolant and the engine running hot.
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 gasses to the coolยญ
ant system.
The operating pressure of the coolant system and the lubricating 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 System).
NOTE: Transmission fluid can also leak into the coolant through radiator bottom tank transmission oil coolers.
