Onan 200 DFP - Page 22

Shut off the air and allow the radiator to refill. Repeat
flushing procedure until the water coming from the
radiator is clean.
To flush the engine block, first remove the thermostat to
allow the water to fill the block. Attach the flushing gun
to the upper radiator hose and fill the block with water.
Restrict the lower radiator hose opening until the block
is filled. Apply air pressure and force water from the
lower opening. Repeat until the water coming from
lower radiator hose is clean.
Replace the thermostat and all hoses and refill cooling
system.
Heat Exchanger Plugs
Check the zinc plugs in the heat exchanger and replace
if they are eroded to less than half their original length.
The frequency of replacement is dependent on the
chemical reaction that occurs when the plugs are in
contact with the raw water.
Coolant Heater
Check the operation of the coolant heater by verifying
that hot coolant is being discharged from the outlet hose
(see Figure 10). For efficient operation and maximum
life, clean the coolant heater whenever the cooling sys¬
tem is drained for flushing.
To Service:
1. Remove AC power from coolant heater.
Failure to remove AC power pre¬
sents a shock hazard and can
cause serious personal injury or death.
2. Allow heater to cool before proceeding.
Contact with hot coolant can
result in serious burns. Do not
bleed hot, pressurized coolant from a closed
cooling system.
3. Remove the head and valve assembly.
4. Clean any scale deposits out of the tank.
5. Remove heating element and scrape off any scale
deposits that have accumulated on the sheathing.
When reassembling threaded aluminum parts, be sure to use
anti>seize compound.
6. R e s tore AC power to heater after system has been
filled with coolant.
^WARNING
A WARNING
TO OIL PLUG
VALVE ASSY
FIGURE 10. COOLANT HEATER
20