20–00 Safety Precautions
Safety Precautions in this section apply to all
procedures within this group.
DANGER
When working on the vehicle, shut down the en-
gine, set the parking brake, and chock the tires.
Before working under the vehicle, always place
jack stands under the frame rails to ensure the
vehicle cannot drop. Failure to follow these steps
could result in serious personal injury or death.
20–01 Radiator Cap Check
WARNING
Do not remove or loosen the radiator cap until the
engine and cooling system have completely
cooled. Use extreme care when removing the cap.
A sudden release of pressure from removing the
cap prior to the system cooling can result in a
surge of scalding coolant that could cause seri-
ous personal injury.
The radiator cap is the most ignored part in the cool-
ing system. If it is suspect, replace it. An inspection
means checking the cap with a pressure tester. A
radiator cap in good condition will not open below 9
psi (62 kPa). A visual check is also in order: look for
signs of deterioration of the inner gasket. Also look
for cracks or breaks in the spring retainer in the cap
and for corrosion or deposits on the spring itself. If
the spring is not in perfect condition, it has probably
lost tension; replace it. See
Fig. 1.
20–02 Radiator Inspection and
Cleaning
Inspect the radiator for clogging or damage and
clean and/or repair it if necessary. Soak the radiator
with a non-corrosive degreaser such as Simple
Green. Let the unit sit for several minutes to work
through the radiator. Using low water pressure, rinse
the radiator. Be careful not to damage or bend the
fins of the radiator. Depending on the condition of the
radiator, this process may have to be performed sev-
eral times.
20–03 Coolant Replacement
At the intervals specified in the maintenance sched-
ule, or whenever the coolant becomes dirty, flush
and refill the cooling system.
NOTE: The coolant replacement interval is in-
creased to 100,000 miles (161 000 km) or 60
months, whichever comes first. For this interval
to apply, you must check and, if necessary, re-
charge the supplemental coolant additive (SCA)
levels and the freeze point every 25,000 miles
(40 000 km) or 6 months, whichever comes first.
See the Cummins Operation and Maintenance
Manual for further information.
WARNING
Do not remove or loosen the radiator cap until the
engine and cooling system have completely
cooled. Use extreme care when removing the cap.
A sudden release of pressure from removing the
cap prior to the system cooling can result in a
surge of scalding coolant that could cause seri-
ous personal injury.
1. Drain the cooling system, as follows.
1.1 When the engine is cool, remove the ra-
diator cap.
Turn the cap slowly counterclockwise until
it reaches a "stop." Do not press down
while turning the cap. Wait until any re-
maining pressure (indicated by a hissing
05/31/2007
f200705
Fig. 1, Surge Tank Coolant Fill Cap
Engine Cooling/Radiator 20
Recreational Vehicle Chassis Maintenance Manual, October 2016 20/1
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