Closed Cooling System; Coolant Requirement - Mercury MerCruiser D2.8L D-Tronic Service Manual

MAINTENANCE

Closed Cooling System

Coolant Requirement

Alcohol or methanol based anti-freeze or plain water are not recommended for use
in the closed cooling section of cooling system at any time.
Because diesel engines are high compression engines and related higher engine operating
temperatures are created, the closed cooling system and engine must remain as clean as
possible to provide adequate engine cooling. This can only be assured by using the proper
anti-freeze, water, additives and inhibitors. It is recommended that the closed cooling
section of the cooling system be filled with a low silicate formula of ethylene glycol
anti-freeze in solution with deionized water. A low silicate formula prevents anti-freeze
separation, which causes a silicate gelatin to form. This gelatin will block engine and heat
exchanger passages causing engine overheating.
The coolant, if not premixed, should be mixed before being added to the closed cooling
system using anti-freeze and deionized water. Common tap water or softened water
contains unwanted minerals, which can leave large deposits in the system restricting the
cooling system efficiency. In addition, additives and inhibitors introduced into acceptable
coolant solutions will form a protective film on internal passages and provide protection
against internal cooling system erosion.
The closed cooling section should be kept filled year-round with an acceptable coolant
solution. Do NOT drain closed cooling section for storage, this will promote rusting of
internal surfaces. If engine will be exposed to freezing temperatures, ensure that closed
cooled section is filled with a properly mixed anti-freeze/coolant solution to protect engine
and closed cooling system to lowest temperature to which they will be exposed.
IMPORTANT: The anti-freeze/coolant used in these marine engines must be a low
silicate ethylene glycol, containing special additives and deionized, purified water.
Using other types of engine coolant may cause fouling of the heat exchangers and
overheating of the engine. Do NOT combine different types of coolants without
knowing that they are compatible. Refer to the coolant manufacturer's instructions.
Some acceptable types of anti-freeze/coolants are listed in the following table. Refer to
Maintenance Schedules for change intervals.
Premixed Marine Engine Coolant
Fleetguard Compleat (Product 91-50663 with DCA4 additive)
Page 1B-28
CAUTION
Description
SERVICE MANUAL NUMBER 22
Part Number
92-813054A2
Obtain Locally
90-860074--1 FEBRUARY 2002