Dodge RAM TRUCK 1500 1995 Service Manual page 285

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COOLING SYSTEM DIAGNOSIS 7 15
COOLING SYSTEM DIAGNOSIS—DIESEL ENGINE—CONTINUED
CONDITION P O S S I B L E CAUSES CORRECTION
HOSE OR HOSES
COLLAPSE WHEN ENGINE
IS COOLING
1. Vacuum created in cooling
system on engine cool-down is
not being relieved through
coolant reserve/overflow
system.
1. (a) Radiator cap relief valve stuck. Refer
to Radiator Cap in this group.
Replace if necessary.
(b) Hose between coolant
reserve/overflow tank and radiator _
kinked. Repair as necessary.
(c) Vent at coolant reserve/overflow tank
is plugged. Clean vent and repair as
necessary.
(d) Reserve/overflow tank is internally
blocked or plugged. Check for
blockage and repair as necessary.
NOISY FAN
1. Fan blades loose.
2. Fan blades striking a
surrounding object.
3. Air obstructions at radiator or air
conditioning condenser.
4. Thermal viscous fan drive has
defective bearing.
5. A certain amount of fan noise
(roaring) may be evident on
models equipped with a thermal
viscous fan drive. Some of this
noise is normal.
1. Replace fan blade assembly. Refer to
Cooling System Fans in this group.
2. Locate point of fan blade contact and
repair as necessary.
3. Remove obstructions and/or clean debris
or insects from radiator or A/C
condenser.
4. Replace fan drive. Bearing is not
serviceable. Refer to Viscous Fan Drive
in this group.
5. Refer to Viscous Fan Drive in this group
for an explanation of normal fan noise.
INADEQUATE AIR
CONDITIONER
PERFORMANCE (COOLING
SYSTEM SUSPECTED)
1. Radiator and/or A/C condenser is
restricted, obstructed or dirty
(insects, leaves etc.).
2. Thermal viscous fan drive is free­
wheeling.
3. Engine is overheating (heat may
be transferred from radiator to
A/C condenser. High underhood
temperatures due to engine
overheating may also transfer
heat to A/C components).
4. Some models with certain
engines are equipped with air
seals at the radiator and/or A/C
condenser. If these seals are
missing or damaged, not enough
air flow will be pulled through the
radiator and A/C condenser.
1. Remove restriction and/or clean as
necessary. Refer to Radiator Cleaning in
this group.
2. Refer to Viscous Fan Drive for diagnosis.
Repair as necessary.
3. Correct overheating condition. Refer to
text in Group 7, Cooling.
4. Check for missing or damaged air seals
and repair as necessary.
J9507-60