Chevrolet 10 Series 1968, Service Manual

Page: 392 / 713

ENGINE COOLING 6K-3
2. Pull Delcotron away from engine until desired ten­
sion reading is obtained with a strand tension gauge.
Refer to “ Engine Tune Up Specifications".
3. Tighten all Delcotron bolts securely.
Thermostat
The thermostat consists of a restriction valve actuated
by a thermostatic element. This is mounted in the hous­
ing at the cylinder head water outlet above the water
pump. Thermostats are designed to open and close at
predetermined temperatures and if not operating properly
should be removed and tested as follows:
Replacement
1. Remove radiator to water outlet hose.
2. Remove thermostat housing bolts and remove water
outlet and gasket from thermostat housing (fig. 2).
3. Inspect thermostat valve to make sure it is in good
condition.
4. Place thermostat in hot water 25° above the temper­
ature stamped on the thermostat valve.
5. Submerge the valve completely and agitate the water
thoroughly. Under this condition the valve should
open fully.
6. Remove the thermostat and place in water 10° below
temperature indicated on the valve.
7. With valve completely submerged and water agitated
thoroughly, the valve should close completely.
8. If thermostat checks satisfactorily, re-install, using
a new housing gasket.
9. Refill cooling system.
Water Pump
Removal
1. Drain radiator and break loose the fan pulley bolts.
2. Disconnect heater hose, lower radiator hose and
by pass hose (as required) at water pump.
3. Loosen Delcotron and remove fan belt then remove
fan bolts, fan and pulley.
NOTE: Thermostatic fan clutches must be kept
in an “ in -ca r" position. When removed from
the car the assembly should be supported so
that the clutch disc remains in a vertical plane
to prevent silicone fluid leakage.
4. Remove pump to cylinder block bolts and remove
pump and old gasket from engine.
F ig . 2—Replacing Thermostat
NOTE: On in line engines, pull the pump
straight out of the block first, to avoid damage
to impeller.
Installation
1. Install pump assembly on cylinder block then, using
a new sealer coated pump-to-block gasket tighten
bolts securely.
2. Install pump pulley and fan on pump hub and tighten
bolts securely.
NOTE: A guide stud (5/16” -24 x 1-1/2” bolt
with the head removed) installed in one hole of
the fan will aid in aligning hub, pulley and
fan. Remove stud after starting the remaining
three bolts.
3. Connect hoses and fill cooling system.
4. Install fan belt and adjust as previously outlined.
5. Start engine and check for leaks.
CHEVROLET TRUCK SERVICE MANUAL