Operation and maintenance manual

Cooling System QSB4.5 and QSB6.7
Page 5-8 Section 5 - Maintenance Procedures at 500 Hours or 6 Months
WARNING
Do not remove the pressure cap from a hot engine.
Wait until the coolant temperature is below 50°C
[122°F] before removing the pressure cap. Heated
coolant spray or steam can cause personal injury.
WARNING
Do not stand near the surge tank or radiator while
operating the engine with the pressure cap off. If the
vehicle is equipped with a fill door on side of the
surge tank, keep it closed due to coolant expansion.
CAUTION
Do not operate the engine with the pressure cap off a
temperatures above 93°C [200°F]. This can result in
potential engine damage by cavitation of the water
pump and localized boiling.
CAUTION
Topping off the system while hot is not recommended
when using the fill door on transit bus applications
equipped with surge tanks. Bringing the level to the
bottom of the door while the system is hot will not
provide adequate volume of coolant for lower
operating temperatures. This can result in cavitation
of the water pump and greatly increase the potential
for engine damage.
CAUTION
Before topping off coolant, allow the system
temperature to cool to ambient. This will make sure
that an adequate amount of coolant is available to the
water pump during all periods of operation.
CAUTION
Engine and component damage may result if
adequate cool down time is not given after the
cooling system pressure has been relieved in order to
"top off". System pressure is ONLY generated with
temperature rise of the coolant, closing the cooling
system while hot will not allow for pressure to build.
Remove the cooling system fill cap.
Fill the cooling system to the capacity or level stated in the
OEM service manual, using a mixture of 50 percent water
and 50 percent ethylene glycol or propylene glycol
antifreeze.