Chevrolet 70 1969 Series, Руководство по ремонту

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ENGINE C O O L IN G SYSTEM 6K-4
C L E A N IN G
1. Drain system, then close cocks and install
drain plugs.
2. Fill system with cleaning solution. Always
follow manufacturer's directions.
3. With radiator covered and radiator cap on
tight, run engine 15 to 20 minutes atfast idle speed.
Drain system completely.
4. If cleaning solution used requires a neu-
tralizer, use as directed by manufacturer.
F LU SH IN G
Before pressure flushing system, tighten cyl­
inder head bolts to prevent possible water leaks
into cylinders and crankcase and remove the ther­
mostats. When pressure flushing, apply air grad­
ually, as radiator will stand only a limited pres­
sure.
CO RRO SIO N PREVENTION
Use of water containing lime, alkali, and other
impurities is a major cause of rust and scale
formation in cooling system. Air or exhaust gas
leaking into the system can also be cause of rust
and corrosion. A rust preventive, inhibitor, or
water filter should be used continuously.
Drain and flush cooling system every 24 months
and add new anti-freeze solution.
INHIBITORS A N D S E A L E R S
In general, inhibitors are not cleaners and
will not remove scale and rust already formed.
G M Cooling System Inhibitor and Sealer will retard
rust and scale formation and is compatible with
aluminum components. Inhibitor and sealer should
be. used immediately after new anti-freeze solution
has been added to system and every fall thereafter.
It is important not to use too much inhibitor
or to use two different types at the same time.
USE INHIBITOR A N D S E A L E R O N L Y AS IN­
S T R U C T E D O N L A B E L .
AIR SU C T IO N TESyT
Air may be drawn into system due to low
liquid level in the radiator or surge tank, leaky
water pump, or loose hose connections. This action
will also cause corrosion.
1. Replace radiator cap having integral pres­
sure relief valve with a plain filler cap less the
relief valve.
2. If a separate pressure relief valve is used,
remove valve and install pressure valve opening
cover. Make sure gasket is in good condition.
3. Make sure radiator cap seal is in good
condition and will make an airtight seal. Adjust
level of cooling liquid in radiator, allowing ample
room for expansion to avoid any overflow loss
during test.
4. Attach a length of rubber tube to lower end
of overflow tube. This connection must be airtight.
Run engine with transmission in neutral at a safe
speed until temperature gauge stops rising and
remains stationary.
5. Without changing engine speed, put end of
rubber tube in a bottle of water, avoiding kinks
and sharp bends that might block flow of air. Watch
for bubbles in bottle of water. The continuous ap­
pearance of bubbles indicates that air is being
sucked into the cooling system.
6. Correct condition by tightening hose clamps
and fitting connections. Also examine all hoses
carefully and if cracked, swollen, or deteriorated
in any way, replace with new hose.
E X H A U S T GAS L E A K A G E T E S T
Exhaust gas may be blown into the cooling
system past cylinder head gasket or through cracks
in the cylinder head and block. This action will
also cause corrosion and possible damage to en­
gine combustion chamber components.
1. Start test with engine cold. Remove drive
belt to prevent water pump operation.
2. On V-6 gasoline models, partially drain
cooling system until cooling liquid level is at top
of thermostat well. Remove thermostats and in­
sure that coolant level is at top of thermostat well.
3. To prepare for test on 6V-53 engine, drain
cooling system to slightly below thermostats, then
remove water outlet castings at thermostat hous­
ings. Remove thermostats and install outlet cast­
ings. Fill system until coolant level is at top of
outlet castings.
4. With transmission in neutral, start engine
and accelerate it several times.
5. Watch for bubbles in water or smoke at
surface of coolant while accelerating engine. Also,
watch when engine speed drops back to idle. The
appearance of bubbles or a sudden rise or fall of
cooling liquid indicates exhaust gas leakage into
cooling system. Make test quickly before boiling
starts as steam bubbles will give misleading
results.
6. If exhaust gas leakage is evident, replace
cylinder head gasket or gaskets, then test again.
Tighten cylinder head bolts to torque specified in
EN G IN E (SEC. 6A or 6B) of this manual. If leaks
are still evident, cylinder head or block may be
cracked. Correct cause of leakage, then install
thermostats and adjust drive belt. Fill radiator.
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L