Maintaining Coolant Level; Pressure Cap Maintenance And Testing - Mercury MerCruiser Service Manual

Maintaining Coolant Level

a
1. Before starting the engine, ensure that coolant is visible in the coolant recovery bottle.
2. If coolant is not visible:
a. Check the closed‑cooling system (including the coolant recovery system) for leaks.
b. Make any necessary repairs.
c. Refill the system with the recommended coolant solution.
3. If coolant is visible:
a. Start the engine and operate it until it reaches its normal operating temperature.
b. Check the coolant level in the coolant recovery bottle. The coolant level must be between the "ADD" and "FULL"
marks on the front of the bottle.
c. If the coolant level is low, remove the fill cap from the coolant recovery bottle and add the required amount of coolant
solution. Refer to Coolant Recommendations.
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.
4. Occasionally, ensure that the coolant recovery system is functioning properly by removing the pressure cap from the heat
exchanger and checking the level. The coolant level should be up to the bottom of the heat exchanger filler neck. If it is
low, examine the entire closed‑cooling section (especially the coolant recovery system) for leaks, and make any necessary
repairs.
IMPORTANT: When reinstalling the pressure cap, tighten it until it contacts the stops on the filler neck.

Pressure Cap Maintenance and Testing

IMPORTANT: Replace the pressure cap if the engine overheats.
The pressure cap is designed to maintain a pressure of approximately its rated capacity once the engine has attained operating
temperature. The cap should be cleaned, inspected and pressure‑tested at regular intervals or whenever the cap is suspected
of not maintaining the proper pressure.
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. Carefully remove the pressure cap from the reservoir or the heat exchanger.
2. Wash the cap with clean water to remove any deposits or debris from the sealing surfaces.
3. Inspect the gasket (if used) and the rubber seal on the cap for tears, cuts, cracks, or other signs of deterioration. Replace
the gasket, if damaged.
4. Replace the cap if the rubber seal is damaged.
90-8M0099748 eng DECEMBER 2015
Coolant recovery bottle
a - Cap
b - "ADD" and "FULL" marks
b
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CAUTION
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CAUTION
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© 2016 Mercury Marine
Models with Closed Cooling
Page 6C-11