Volvo Penta D1-20 Operator's Manual page 36

Maintenance: Freshwater system
2
D1-20, D1-30 & D2-40
34
1
3
D1-13
3
2
Coolant. Draining
Connect a hose to the engine drain cock(1) and
another to the heat exchanger drain tap (2) and lower
these into a vessel. Remove the filler cap on the heat
exchanger to let the coolant run out faster. Open the
drain cock (1) and the drain tap (2) and drain off all
coolant. Before new coolant is put in, clean the heat
exchanger as in the following paragraphs.
NOTE! Deposit old coolant at a properly designated
disposal site.
Heat exchanger. Cleaning
Cooling performance is reduced by scaling in the heat
exchanger. It should therefore be flushed when the
coolant is changed.
1. Drain the coolant as above.
2. Insert a hose into the filling pipe (3) on the heat ex-
changer. Rinse with fresh water until the water
which runs out of the drain tap and the engine
block is clean. Let all the water run out.
3. Close the drain tap and the drain plug. Fill up with
coolant to the correct level. Put the filler cap back.