Onan MJA Series Service Manual page 27

COOLING SYSTEM
25
3.1.4.3 Repair and Testing, Raw Water System. - Test for air leaks
and insuffiCient water flow as described in Sect 3.1.2. Repair of the
rubber iI:hpeller pump was covered in Sect 3.1.3.2.
3.1.4.4 Heat Exchanger Repair. - The heat exchanger should never
require any repair under normal service conditions. However, if it
­
should become clogged, remove the ends and clean out the tubes .
3.1.4.5 Centrifugal Pump Repair. - The centrifugal fresh water pump
is mounted on the heat exchanger bracket. If it should leak, or the
bearings require replacement, disassemble
it
and replace the worn
components.
"
Pump Disassembly
1. Remove the water inlet from the pump and remove the 6 screws
holding the end cover to the pump.
2. Unscrew the impeller from the shaft counterclockwise when facing
the impeiler.
3. Remove the pump body by unscrewing the single capscrew that
clamps the pump body to the pedestal.
4. Remove the retaining ring and drive the bearing assembly out of the
pedestal.
5. To remove the water seal, drive
it
out of the pump body.
Replace the worn components. When replaCing the water seal, check
the wear plate pressed into the impeller and replace
it if
necessary.
To assemble tbepump, reverse the disassembly procedure.
3.1.4.6 Thermostats and Expansion Tank. - On the MJA and MJB, the
expansion tank serves as the thermostat housing. On the MJC, it houses
the thermostat for the front 2 cylinders.
To remove the expansion tank, remove the 2 capscrews extending down
through the tank. For thermostat testing and repair, see Sect 3.1.3.1.
When reinstalling the tank, be sure aU connections are tight.
Check the expansion tank fill cap. This is a pressurized cap, designed
to hold 12-15 psi. The correct cap, good gaskets and smooth gasket
surfaces are essential to prevent loss of water.