GMC 1976 ZEO 6083 Maintenance Manual page 334

COOLING SYSTEM TROUBLE DIAGNOSIS
ENGINE COOLING
6K- 3
Problem
Possible Cause Correction
Engine overheats (En-
Loss of coolant. See "Loss of Coolant" condition
gine temperature gauge
below. Pressure check system with
indicates coolant tem-
suitable checking equipment. Cor-
perature is HOT or rect as necessary.
coolant overflows from
reservoir onto ground
while engine is
running) .
Low coolant protection Test solution . Add 50/50 coolant/
(should be -34°F.) water solution as required.
(-36°C .) Belt Check with BT-33-73F. Adjust if
tension too low.
loose.
Ignition timing retarded . Set timing to specifications . See
"Engine Electrical" later in this
manual .
Timing retarded by stick-
Check and correct. See "Engine
ing or inoperative vacuum Electrical" later in this section.
or mechanical advance.
Thermal Vacuum Switch Test and replace if necessary. See
(T .V .S.) not switching.
"Thermal Vacuum Switch" later in
this section .
Radiator fins obstructed . Clean away bugs, leaves, etc.
Flush system-add fresh coolant.
Cooling system passages
Flush system-add fresh coolant.
blocked by rust or scale.
Reservoir hose pinched or
Relieve kinks by re-routing .
kinked (especially at
Replace if permanently kinked .
radiator filler neck).
Lower radiator hose
Check for hose spring position by
collapses. squeezing lower end of hose .
Replace if necessary.
Defective fan clutch . Replace fan clutch .
Loss of coolant.
Leaking radiator . Inspect cooling system . Repair or
replace as required .
Radiator cap defective,
Pressure check radiator and cap
or filler neck distorted.
with suitable testing equipment. If
neck upper sealing area is dis-
torted, use wood block and mallet
to reform evenly so cap will fit.
Leaking coolant reservoir
Replace reservoir or hose .
or hose .
Loose or damaged hoses or
Reseat or replace hoses or clamps .
connections.
Include hoses to pre-heater if
equipped .
Water pump seal leaking. Replace water pump .
Water pump gasket leaking. Replace gasket .
Improper cylinder head
Torque bolts to 85 ft . lbs.
bolt torque .