Cooling System Diagnosis - Dodge D150 1990 Service Manual

7 - 4 COOLING SYSTEM
COOLING S Y S T E M DIAGNOSIS
CONDITION AND CHECK DIAGNOSIS
OPTIONAL 60°F GAUGE READS LOW
30° TO 40°
GAUGE TRAVEL
IS NORMAL
(1) Verify gauge reeding. Is a low temperature indicated?
(2) Is code 17 recorded in On Board Diagnostics memory?
(3) Is the gauge reading in the cold range?
(4) Low coolant level during cold ambient temperatures
(accompanied with poor heater performance).
(5) Coolant level is correct.
MID
Normal Gauge Travel
(1) Inspect temperature gauge sending unit. Refer to Group 8,
Electrical. Repair or replace sending unit as necessary.
(2) If code 17 is recorded, replace the thermostat. If not, the
thermostat is not the cause of the low gauge reading.
(3) Inspect for disconnected sending unit electrical connector or
incorrect sending unit. Ensure that gauge sending unit is installed
and not an indicator light switch.
(4) WARNING: DO NOT REMOVE THE RADIATOR CAP OF A
HOT, PRESSURIZED ENGINE. SERIOUS INJURY CAN
RESULT FROM SCALDING COOLANT.
Inspect coolant level in the coolant reserve tank and radiator.
Inspect system for leaks.
(5) Inspect heater door controls. Refer to Group 24, Heating and
Air Conditioning.
GAUGE READING HIGH. NO PRESSURE BLOW OFF FROM
RADIATOR PRESSURE CAP OR STEAM FROM COOLANT
RESERVE TANK.
MAXIMUM HOT
WEATHER
HEAVY LOAD
(1) Verify gauge reading. Is a high temperature reading indicated?
(2) Gauge reading at "H" without signs of boiling.
(3) Low coolant level in radiator and coolant reserve tank.
(4) Coolant level in radiator is low. But not low in coolant reserve
tank.
(5) Test coolant freeze point.
(6) Ensure proper coolant flow.
MAXIMUM UP
TO TOP AMBIENT
High Gauge Reading — Hot Weather — Heavy Load
(1) Compare gauge reading to High Gauge Reading Illustration
above.
(2) Inspect for grounded gauge, sending unit or circuit. Refer to
Group 8, Electrical.
(3) a — Fill to full.
b — Inspect for leaks in system and repair as necessary,
c — Ensure radiator pressure cap was shut tight. Verify proper
operation of the rodiator cap upper and lower seals.
(4) a — Fill to full.
b — Inspect for leaks in the system and repair as necessary,
c — Inspect for leaks in the coolant reserve tank to radiator
hose.
d — Verify proper operation of the radiator cap upper and
lower seals.
(5) a — Adjust coolant solution to 50/50 mixture of anti-freeze and
water. Refer to Coolant in this group,
b — If a reading is not recorded or below — 50, the mixture is
too rich. Clean system and fill with a 50/50 mixture of
anti-freeze and water. Refer to Coolant in this group.
(6) a — With the thermostat open and a slight amount of coolant
removed, inspect for coolant flow through the radiator at
the filler neck opening,
b — Determine reason for lack of coolant flow and repair as
necessary.
J9007-69