Dodge D250 1990 Service Manual page 110

Cooling System
DODGE Turbo Diesel
Install the pressure cap. Start the engine and operate it until it
reaches a temperature of 83°C [181°F]. Check the system for
leaks.
Warning: If the engine h a s been operating and the
coolant is hot
y
wait until the temperature Is below 50°C
[120°F] before removing the pressure cap. Failure to do
so ran cause personal Injury from heated coolant spray.
Caution: R e - c h e c k the cooling system to insure total
system is full of coolant
Cooling System Replacement Procedures
Page 7-21