Replacing The Engine Coolant In The Closed-Cooling System; Draining The Closed-Cooling System - Mercury MerCruiser Diesel Inboard 2.8L Operation & Maintenance Manual

Section 4 - Maintenance
Replacing the Engine Coolant in the Closed‑Cooling System
Draining the Closed‑Cooling System
Discharge of oil, coolant, or other engine/drive fluids into the environment is restricted by law. Use caution not to spill oil,
coolant, or other fluids into the environment when using or servicing your boat. Be aware of the local restrictions governing
the disposal or recycling of waste, and contain and dispose of fluids as required.
NOTE: For instructions on draining the seawater section, refer to Draining the Seawater System in this section.
IMPORTANT: Observe the following points.
• Ensure that the engine is as level as possible to promote complete draining of the cooling system.
• The closed‑cooling section must be filled year‑round with the required coolant. If the engine will be exposed to freezing
temperatures, ensure that the closed‑cooling section is filled with a solution of ethylene glycol antifreeze and water properly
mixed to protect the engine to the lowest temperature to which it will be exposed.
• Do not use propylene glycol antifreeze in the closed‑cooling section of the engine.
A sudden loss of pressure can cause hot coolant to boil and discharge violently, resulting in serious injury from burns. Allow
the engine to cool down before removing the coolant pressure cap.
1. Allow the engine to cool.
2. Remove the pressure cap from the expansion tank and coolant reservoir.
NOTE: Drain coolant into a suitable container. Dispose of old coolant properly.
3. Remove the intake and exhaust manifold drain plug.
4. Remove the heat exchanger drain plug.
a
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NOTICE
CAUTION
!
4.2L shown, 2.8L similar
a - Intake and exhaust manifold drain plug
b - Fluid cooler drain plug
b
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90-8M0133679 JUNE 2017
eng