Filling Closed Cooling Section - Mercury MerCruiser MCM 454 Mag MPI Service Manual

CLOSED COOLED (FRESH WATER) MODELS

Filling Closed Cooling Section

Alcohol or Methanol base antifreeze or plain water are not recommended for use in
coolant section of Closed Cooling System at any time.
It is recommended that coolant section of Closed Cooling System be filled with a 50/50 mix-
ture of Extended Life 5/100 Coolant and pure, soft water. This coolant MUST BE used re-
gardless of whether freezing temperatures are or are not expected to provide adequate cor-
rosion protection. In areas where Extended Life 5/100 Coolant is not available and the
possibility of freezing DOES NOT exist, it is permissible to use a solution of rust inhibitor and
pure, soft water (mixed to manufacturer's recommendations).
NOTE: Coolant section capacity is approximately 18 U.S. Quarts (17 L).
1. Fill coolant section of Closed Cooling System with coolant mixture as follows:
a. Open bleeder valve on thermostat housing.
b. Fill with coolant mixture through heat exchanger fill neck until coolant appears at
c. Close bleeder valve securely.
d. Continue filling until coolant level is into filler neck and begins to flow into coolant
DO NOT operate engine without water flowing through seawater pickup pump, as
pump impeller may be damaged and subsequent overheating damage to engine or
sterndrive unit may result.
Front of engine should be higher than rear to purge trapped air out of the system
during initial filling. This will minimize the possibility of air being trapped in the
closed cooling section which can cause engine to overheat.
IMPORTANT: This closed cooling system flows coolant at a high rate. Higher idle
speeds increase dispersion of trapped air into system making it more difficult to
purge trapped air. Operate at idle during filling and air purging when specified.
Index
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a - Hex Head Bleeder Valve
bleeder valve opening.
recovery bottle plastic tubing.
CAUTION
a
CAUTION
CAUTION
SERVICE MANUAL NUMBER 23
75598
90-861326--1 MARCH 1999