Cleaning System; Closed Cooling Section - Mercury MerCruiser MCM 454 Mag MPI Service Manual

CLOSED COOLED (FRESH WATER) MODELS
IMPORTANT: Engine must be as level as possible to ensure complete draining of
cooling system.
IMPORTANT: Closed cooling section must be kept filled year round with recom-
mended coolant. If engine will be exposed to freezing temperatures, make sure
closed cooling section is filled with Extended Life 5/100 Coolant or an ethylene glycol
antifreeze and water solution properly mixed to protect engine to lowest temperature
to which it will be exposed.
The following draining instructions apply to all engines equipped with closed cooling. The
location of petcocks that require opening and hoses that require removal are represented
on the following pages for the individual engines.
IMPORTANT: Observe precautions previously outlined before proceeding.
1. Remove pressure cap from coolant tank.
2. Drain coolant from locations as shown in the "Draining Diagram."
3. After coolant has drained completely, reinstall petcocks and hoses. Tighten clamps and
petcocks securely.
4. Remove coolant recovery bottle from mounting bracket and pour out coolant.
5. Clean system as outlined in "Cleaning System."
6. Fill system as outlined in "Filling Closed Cooling Section."

Cleaning System

Closed Cooling Section

Closed cooling section of closed cooling system should be cleaned at least once every two
years or whenever decreased cooling efficiency is experienced.
A good grade automotive cooling system cleaning solution may be used to remove rust,
scale or other foreign material. Always follow manufacturer's instructions for the cleaner.
If closed cooling section is extremely dirty, a pressure flushing device may be used to flush
out remaining deposits. Flushing should be done in direction opposite normal coolant flow
to allow water to get behind deposits and force them out. Refer to instructions which accom-
pany flushing device for proper hookup and flushing procedure.
For information and procedures for draining and flushing Seawater Section of
Closed Cooling (Coolant) Models, refer to SECTION 1B. For cold weather or
extended storage, refer to SECTION 1B.
Index
Page 6B-14
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NOTICE
SERVICE MANUAL NUMBER 23
90-861326--1 MARCH 1999