GMC 4000 Series Service Manual page 550

After thawing, refill system with a higher concen­
tration of anti-freeze solution and start engine.
Inspect entire system for leakage and then test
coolant with hydrometer to determine if adequate
anti-freeze protection is provided.
COOLANT PRECAUTIONS
1. Overheating is not always caused by a de­
fective cooling system ; incorrect ignition timing,
dragging brakes, under-inflated tires, and improper
use of transm ission gears can cause overheating.
2. Keep water pump and fan drive belts at
proper tension. Refer to ENGINE COOLING SYS­
TEM (SEC. 6K) of this manual.
3. Do not o ver-fill cooling system . Expansion
of coolant when hot will cause lo ss of coolant through
overflow tube.
MODELS
PS4500
All Other Models
G M C S E R V I C E M A N U A L
SPECIFICATIONS
CO O LIN G SY ST EM P R ESSU R E R E L IE F V A L V E
VALVE STAMPED
RC-6-13#
RC-12-9#
RADIATOR A N D SURGE TANK
4. Do not remove radiator filler cap when en­
gine is hot. Wait until system cools off.
5. Do not pour cold water into cooling system
when the engine is hot. Wait until system cools off.
6. If cooling system requires frequent refill­
ing, check for leaks.
7. Keep all connections tight, and make sure
gasket on radiator filler cap is in good condition.
8. When filling system with anti-freeze solu­
tion ALWAYS FOLLOW RECOMMENDATIONS of
anti-freeze manufacturer.
9. Use only Ethylene Glycol base coolant meet­
ing GM Specification 1899-M. DO NOT use Glycol
Ether (Methoxy Propanol Type) in Toro-Flow II
engines.
10. Drain and flush cooling system every other
year, preferably at start or end of winter operation.
OPENING PRESSURE
13 psi
9 psi
Sec. 13
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