Freshwater Pump Removal/Installation; Freshwater Cooling System Maintenance; Pressure Testing - Yanmar 1GM10 Shop Manual

COOLING SYSTEM
peller counterclockwise. Be certain all impeller blades are
facing the same direction (Figure 27).
24. Install the cover (1 8, Figure 28) and gasket.
25. Install the six screws securing the pump cover to the
body.
FRESHWATER PUMP
The freshwater circulating pump may warn of impend-
ing failure by making noise. If the seal is defective, cool-
ant or water may leak from behind the pump pulley. It is
recommended that the pump be replaced as an assembly.
Individual replacement parts are available.
1. Drain the freshwater cooling system. Refer to Chapter
Four.
NOTE
proceed to Step 3.
2. Loosen, but do not remove, the pump pulley retaining
bolts (A, Figure 29).
3. Loosen the alternator adjusting and pivot bolts (B, Fig-
ure 29). Swivel the alternator toward the engine and re-
move the drive belt from the pump pulley.
4. Unscrew the pump pulley screws and remove the pul-
ley.
5. Unclamp and disconnect the hoses from the circulating
pump and detach any hose brackets that interfere with ac-
cess to the water pump bolts.
NOTE
Note the length ofthe pump retaining bolts
during removal and, if necessary, mark
them according to location.
6. Remove the pump retaining bolts (Figure 30). Re-
move the pump and gasket. Discard the gasket.
7. Clean all gasket residue from the pump and engine
block mounting surfaces.
8. Installation is the reverse of removal. Tighten the wa-
ter pump fasteners to the tightening torque specified in
Table 1. Adjust drive belts as described in Chapter Three.
Fill the freshwater section of closed cooling systems with
coolant. See Chapter Three. Start the engine and check for
leaks.
FRESHWATER COOLING SYSTEM
MAINTENANCE

Pressure Testing

If the freshwater (closed) cooling system requires fre-
quent topping off, it probably has a leak. Small leaks in a
cooling system are not easy to locate; the hot coolant
evaporates as fast as it leaks out, preventing the formation
of tell-tale rusty or grayish-white stains.
A pressure test of the freshwater section will usually
help to pinpoint the source of the leak. The procedure is
very similar to that used in pressure testing automotive
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