W 250 Pickup L6-359 5.9L DSL (1989)
Radiator Cap: Testing and Inspection
The system is designed to use a pressure cap to prevent boiling of the coolant.
An incorrect or malfunctioning cap can result in the loss of coolant and the engine running hot.
The cap specified for this system is:
System
Cap
110°c [230°F]
103kPa [15 PSI]
Air in the coolant can result in loss 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 coolant 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.
NOTE: Transmission oil can also leak into the coolant through a faulty transmission oil cooler.
