GMC 4000 Series Service Manual page 326

OUTLET
ENGINE OIL COOLER
Models with an oil cooler use type of oil cool­
ing system shown in figure 6. Oil is filtered, c ir ­
culated through oil cooler, and returned to engine.
If engine difficulties are encountered and there
is suspicion that foreign matter has entered the oil
cooler, the oil cooler and connecting lines must be
flushed before engine is put back into operation.
Oil cooler, located at bottom of radiator core,
should be flushed in the following manner:
1. Disconnect oil cooler lines at oil filter.
2. Back-flush oil cooler and lines using clean
solvent and compressed air. DO NOT EXCEED
100 PSI AIR PRESSURE.
3. Remove all remaining cleaning solvent from
the system with compressed air.
4. Flush system again with the same type of
oil normally circulated through the cooler.
5. Test flow of oil through cooler. If flow is
not restricted, reconnect oil cooler lines. If flow
is restricted, have oil cooler element replaced by
a radiator specialist.
FAN AND DRIVE BELTS
FAN BLADE
Fan blade assembly is bolted directly to water
pump pulley on all models except tilt cab models.
Fan blade on tilt cab models is bolted to engine
crankshaft pulley hub.
DRIVE BELT TENSION ADJUSTMENT
Drive belts must be kept at proper tension. A
G M C S E R V I C E M A N U A L
Figure 5 — Water Filter Assem bly (Typical)
loose or broken drive belt will affect operation of
driven accessory. A drive belt that is too tight will
place excessive str ess on bearings within a c c e ss­
ory.
an accurate belt tension dial gauge.
are adjusted to 120 to 130 pounds tension for new
belts and 80 to 90 pounds tension for used belts.
New belts are adjusted to a higher tension to allow
for stretch in the belt. As stretch occurs, tension
should decrease to 80 to 90 pounds.
stalled new belts, check tension of belts twice in
first 200 m iles of operation.
place if frayed or worn.
ENGINE COOLING SYSTEM
1 Cover Bolt
2 Cover
3 Cover Gasket
4 Upper Plate
5 Element
6 Lower Plate
7 Spring
8 F ilter Body
9 Plug
Belt tension adjustments should be made with
Fan and generator drive belts for all models
NOTE: On a new vehicle or after having in­
When making adjustment, examine belts. Re­
Figure 6 — O il Cooler Circuit
Sec. 6K
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