Uncommon Cooling System Problems - GMC G Service Manual

6B1-6 ENGINE COOLING
COOLING SYSTEM DIAGNOSIS - CHART B
C OOLANT LOSS
X
CHECK PRESSU RE CAP
OK
VISUAL SYSTEM CHECK
i .. .
.................
1. LEAKS - - CHECK HOSES, RADIATOR,
CLAMPS, W ATER PUMP, THERM OSTAT
HOUSING, RADIATOR DRAIN, SOFT OR
CO RE PLUGS, HEATER W ATER VALVES,
H EATER CORE.
2. FOAMING CO O LAN T - O BSERVE IN THE
FILLER NECK AFTER ENGINE WARMUP.
3. O VE R FLO W SYSTEM - (SEMI-SEALED
SYSTEM)
A. CHECK FOR GASKET IN PRESSU RE CAP.
B. CHECK FOR LEAKS - HOSES, CLAMPS,
O VER F LO W BOTTLE, FILLER NECK NIPPLE.
C. CHECK FOR O BSTRUC TIONS OR
PLUGGING IN THE HOSE BETW EEN THE
RADIATOR AND BOTTLE.
R EPAIR OR
REPLACE DEFECTS
PRESSU RE CHECK SYSTEM
INSTALL P RE SSU RE CAP
CHECKER ON THE RADIATOR
FILLER NECK AND PRESSU RIZE
THE SYSTEM TO RATED
PRESSURE. IF THE SYSTEM
DOES N OT HOLD PRESSURE.
LOOK FOR THE LEAK LOCATION.
OK
A N Y REPAIRS?
Y ES
I
SYSTEM IS OK
Figure 4 — Cooling System Diagnosis Chart
PROBLEMS NOT REQUIRING DISASSEMBLY OF THE
COOLING SYSTEM
BAD
=r=
1. Locate and remove large external obstructions block­
REPLACE
1
2. Engine oil is over-filled.
3. Incorrect radiator for the application.
4. Loose, damaged, or missing air seals.
5. Missing or damaged lower air baffle.
6. Incorrect ignition timing.
PROBLEMS REQUIRING DISASSEMBLY OF THE
COOLING SYSTEM
1. Incorrect or damaged fan.
2. Worn or damaged emission system components.
3. Pressure-check the cooling system with the pressure
LEAKS
REPAIR
4. Worn or damaged water pump.
5. Plugged radiator tubes.
6. Internal system leaks.
7. Plugged coolant passages in the cylinder heads.
F-02620
UNCOMMON COOLING
SYSTEM PROBLEMS
ing the radiator or the condenser.
• Auxiliary oil cooler.
• License plates.
• Spare tires.
• Ice, mud, or snow obstructing the grille.
• Check the part number.
• Damaged PCV valve, TVS or TCS.
• Malfunctioning emission system components
could cause overheating at idle.
cap installed.
• Shows if the pressure cap leaks because of
radiator filler neck damage.
• Impeller vanes eroded or broken.
• Worn or damaged bearing and/or seal — check
for shaft or bearing play.
• Perform a flow check.
• Head gasket.
• Cracked block.
• Timing chain cover.
• Intake manifold gasket.
• Visual check.