Usage:
3116 (4KG, 1SK) Marine Engines
Many times cracked exhaust manifolds and/or damaged cylinder head gaskets are caused by the engine overheating. This overheating may be due to reduced water flow from loss of coolant or from excessive air entrained in the cooling water. Therefore, simply replacing the cracked exhaust manifold or damaged head gasket may not fix the problem unless the underlying cause of the engine overheating is identified and corrected.
Anything that contributes to coolant loss or air in the coolant could be a contributor to cracked exhaust manifolds and damaged head gaskets. See the following possible Cooling System problems and solutions:
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- 1. COOLANT LOSS FROM "AFTERBOIL"
- 2. COOLANT LOSS FROM LEAKAGE DUE TO A DAMAGED COMPONENT
- 3. AIR VENTING/COMBUSTION GAS LEAKAGE
- 1. COOLANT LOSS FROM "AFTERBOIL"
1. COOLANT LOSS FROM "AFTERBOIL"
When engine power and speed are quickly reduced from Cruise or Full Load to Low Idle or No Wake rpm, the full heat load is still in the engine but the cooling water flow is greatly reduced. This can result in localized boiling of the coolant ("afterboil") in the hot parts of the cylinder head, exhaust manifold, and turbocharger. The boiling coolant produces steam, which may push coolant out of the engine. This is more common in work boat applications where time is money, but some "hot rod" pleasure boat operators may also operate a boat this way when coming into a low wake zone or to the docks. Recommendations for these applications are:
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- * The Operation And Maintenance Manual Maintenance Schedule calls for checking the coolant level in the expansion tank DAILY! This is the customer's responsibility.
- * A 102-9223 Coolant Recovery Group will catch most of the coolant pushed out of the engine by "afterboil" and return the coolant to the expansion tank when the engine cools.
- * A Coolant Level Sensor (and alarm) will warn the operator of coolant loss while underway, or of a sudden loss of coolant where the water temperature gage may not record the elevated temperatures. The part numbers are:
- * The Operation And Maintenance Manual Maintenance Schedule calls for checking the coolant level in the expansion tank DAILY! This is the customer's responsibility.
- - 121-4366 Liquid Level Sensor Group [Parts Service for 3116 (4KG01500-Up)].
- - 123-0501 Electronic Low Coolant Sensor Group. Note, this group must be ordered when the 3116 Marine Engine is ordered. This group is not available for parts service.
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- * When the engine is initially filled with coolant (new engine or after rework), the engine should be:
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- 1. Filled with coolant.
- 2. The engine should be run and warmed up to operating temperature.
- 3. The coolant should be "topped off" after engine cools off and it is safe to open pressure cap.
- 1. Filled with coolant.
- * The expansion tank pressure cap must be functioning properly.
2. COOLANT LOSS FROM LEAKAGE DUE TO A DAMAGED COMPONENT
After exhaust manifold or cylinder head gasket repair, the cooling system should be checked for other leaks using 9S-8140 Cooling System Pressurizing Pump Group. See Service Manual Module, Systems Operation, Testing And Adjusting, SENR3583, "Cooling System".
3. AIR VENTING/COMBUSTION GAS LEAKAGE
A rear cylinder head vent line was added on 3116 (4KG4351-Up) Marine Engines. This vent line was modified on 3116 (4KG4471-Up) Marine Engines to include a vent from the rear of the exhaust manifold to help vent air out of the engine. Adding this vent to earlier engines may require drilling and taping of a 1/8inch NPT in the cylinder head and/or exhaust manifold. Part numbers of the components required for the vent line are identified in Chart A.
History Of Cooling System Improvements
Other improvements have been made to help prevent coolant loss and air in the engine coolant in these engines. Chart B identifies the engine serial number when the improvement became effective.
