Operation and maintenance manual

QSB4.5 and QSB6.7 Radiator Pressure Cap
Section 5 - Maintenance Procedures at 500 Hours or 6 Months Page 5-15
Pressure-test the radiator cap. Refer to the OEM service
manual for radiator cap test procedures.
The pressure cap must seal within 14 kPa [2 psi] of the
value stated on the cap, or it must be replaced.
An incorrect or malfunctioning cap can result in the loss of
coolant and the engine running hot.