Onan MDKBH Series, Service Manual

Page: 33 / 90

4-8
Replacing the Thermostat
WARNING
Accidental or remote starting can
cause severe personal injury or death. Discon-
nect the negative (–) cable from the battery to
prevent the engine from starting.
WARNING
Hot coolant spray can cause severe
burns. Let the engine cool before releasing the
pressure cap or removing the drain cap.
See Table 4-1 for scheduled replacement. Refer-
ring to Figure 4-5, replace the thermostat as follows:
1. Disconnect the negative ( – ) cable at the battery
to prevent the engine from starting, let the en-
gine cool and remove the top access door and
pressure cap.
2. Remove the two thermostat housing bolts and
pull off the housing, thermostat and gasket. The
hose does not need to come off.
3. Clean off the gasket area and install the new
thermostat and gasket. Apply Three Bond 1215
liquid sealant or equivalent to the top side of the
gasket.
4. Replenish any lost coolant, secure the pres-
sure cap, secure the access door and recon-
nect the battery cables (negative [ – ] last).
Siphon Break
WARNING
Bypassing a siphon break or failing
to maintain it can lead to engine flooding and
damage to the engine not covered under War-
ranty.
See Table 4-1 for scheduled maintenance. A siphon
break is installed when the exhaust-water mixer is
below the water line. If of a spring-loaded valve de-
sign, check for free movement of the plunger. Re-
place the device if the plunger does not move freely
or the body is encrusted with deposits from leakage
past the valve seat. If of the bleed-vent type, check
that the vent hose is properly connected on both
ends. If the vent is connected to a through-hull fit-
ting, check for normal water flow whenever the en-
gine is running. See the Installation Manual for more
information regarding siphon break installation.
THERMOSTAT
FIGURE 4-5. TYPICAL THERMOSTAT
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