Chevrolet 10 Series 1968, Руководство по обслуживанию

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ENGINE COOLING 6K-2
form acids which are particularly harmful to
the radiator and engine.
3. To check for exhaust leaks into the cooling system,
drain the system until the water level stands just
above the top of the cylinder head, then disconnect
the upper radiator hose and remove the thermostat
and fan belt. Start the engine and quickly accelerate
several times. At the same time note any appreci­
able water rise or the appearance of bubbles which
are indicative of exhaust gases leaking into the cool­
ing system.
Periodic Maintenance
It is the owner's responsibility to keep the freeze
protection at a level commensurate with the area in
which the vehicle will be operated. Regardless of c li­
mate, system protection should be maintained at least to
0°F., to provide adequate corrosion protection. When
adding solution due to loss of coolant for any reason or
in areas where temperatures lower than -20°F. may
occur, a sufficient amount of an ethylene glycol base
coolant that meets GM Specification 1899-M should be
used.
In areas where anti-freeze is not required, adequate
engine system corrosion protection may be maintained
by using a corrosion inhibitor which meets all require­
ments of GM Specification 1894-M.
Every two years the cooling system should be serv­
iced by flushing with plain water, then completely re ­
filled with a fresh solution of water and high-quality
inhibited (permanent-type) glycol base coolant meeting
GM Specification 1899-M, and providing freezing pro­
tection at least to 0°F. At this time, also add GM Cooling
System Inhibitor and Sealer or equivalent. In addition,
every fall thereafter GM Cooling System Inhibitor retards
the formation of rust or scale and is compatible with
aluminum components.
NOTE: Alcohol or methanol base coolants or
plain water are not recommended for your
cooling system at any time.
Two common causes of corrosion are: (1) air suction—
A ir may be drawn into the system due to low liquid level
in the radiator, leaky water pump or loose hose con­
nections; (2) exhaust gas leakage--Exhaust gas may be
blown into the cooling system past the cylinder head
gasket or through cracks in the cylinder head and block.
Cleaning
A good cleaning solution should be used to loosen the
rust and scale before reverse flushing the cooling sys­
tem. There are a number of cleaning solutions available
and the manufacturer's instructions with the particular
cleaner being used should always be followed.
An excellent preparation to use for this purpose is GM
Cooling System Cleaner. The following directions for
cleaning the system applies only when this type cleaner
is used.
1. Drain the cooling system including the cylinder block
and then close both drain plugs.
2. Remove thermostat and replace thermostat housing.
3. Add the liquid portion (No. 1) of the cooling system
cleaner.
4. F ill the cooling system with water to a level of about
3 inches below the top of the overflow pipe.
5. Cover the radiator and run the engine at moderate
speed until engine coolant temperature reaches
180
degrees.
6. Remove cover from radiator and continue to run the
engine for
20
minutes. Avoid boiling.
7. While the engine is still running, add the powder
portion (No. 2) of the cooling system cleaner and
continue to run the engine for 10 minutes.
8. At the end of this time, stop the engine, wait a few
minutes and then open the drain cocks or remove
pipe plugs. Also remove lower hose connection.
CA U TIO N : Be careful not to scald your hands.
NOTE: Dirt and bugs may be cleaned out of
the radiator air passages by blowing out with air
pressure from the back of the core. Do not
bend radiator fins.
Reverse Flushing
Reverse flushing should always be accomplished after
the system is thoroughly cleaned as outlined above.
Flushing is accomplished through the system in a direc­
tion opposite to the normal flow. This action causes the
water to get behind the corrosion deposits and force
them out.
Radiator
1. Remove the upper and lower radiator hoses and re­
place the radiator cap.
2.
Attach a lead-away hose at the top of the radiator.
3. Attach a new piece of hose to the radiator outlet
connection and insert the flushing gun in this hose.
4. Connect the water hose of the flushing gun to a water
outlet and the air hose to an air line.
5. Turn on the water and when the radiator is full, turn
on the air in short blasts, allowing the radiator to
fill between blasts of air.
CA U TIO N : Apply air gradually as a clogged
radiator will stand only a limited pressure.
6. Continue this flushing until the water from the lead-
away hose runs clear.
Cylinder Block and Cylinder Head
1. With the thermostat removed, attach a lead-away
hose to the water pump inlet and a length of new hose
to the water outlet connection at the top of the engine.
NOTE:
Disconnect the heater hose and cap
connections at engine when reverse flushing
engine.
2.
Insert the flushing gun in the new hose.
3. Turn on the water and when the engine water jacket
is full, turn on the air in short blasts.
4. Continue this flushing until the water from the lead-
away hose runs clear.
Hot W ater Heater
1. Remove water outlet hose from heater core pipe.
2.
Remove inlet hose from engine connection.
3. Insert flushing gun and flush heater core. Care must
be taken when applying air pressure to prevent
damage to the core.
Fan Belt
Adjustment
1.
Loosen bolts at Delcotron mounting.
CHEVROLET TRUCK SERVICE MANUAL