Usage:
Water pump inlet pipe (13) is connected to the expansion tank outlet. Coolant from the pump (12) flows through the piping to oil cooler (11). On D399 Engines, a portion of the coolant from the piping is directed into cylinder block (10). The flow from the oil cooler is to flywheel housing (9).
FLOW OF COOLANT (SCHEMATIC)
1-Aftercooler. 2-Elbow. 3-Exhaust manifold. 4-Cylinder head. 5-Bypass line. 6-Temperature regulator housing. 7-Expansion tank. 87ndash;Marine gear oil cooler. 9-Flywheel housing. 10-Cylinder block. 11-Oil cooler. 12-Water pump. 14-Inlet pipe. 14-Raw water pump. 15-Heat exchanger.
The flywheel housing has two separate passages. The upper passage directs the flow of coolant to the junction housing, at the left side of the flywheel housing. From the upper connection of the junction housing, when equipped with a fresh water aftercooler, part of the flow is directed through the pipe to the front core of the aftercooler (1). The crossover pipe, on the right side of the aftercooler, directs the flow through the rear core. Coolant then flows through the pipe connected to the lower connection of the junction housing where it joins with the bypassed coolant from the flywheel housing upper passage.
NOTE: On engines equipped with a raw water cooled aftercooler, all coolant turns 180° at the left side of the flywheel housing and flows back across the housing through the lower passage. See the topic RAW WATER SYSTEM.
Coolant flows back across the flywheel housing through the lower passage where the flow is divided, an equal part going to each bank of cylinders of the cylinder block.
On engines equipped with attachments that have heat exchanger-type oil coolers such as a marine gear oil cooler (8). which requires fresh water, an adapter is attached to the left side of the flywheel housing. Part of the coolant flows through the cooler and is then directed back to the lower passage of the flywheel housing and then directed to the cylinder banks on each side of the cylinder block (10).
The coolant then circulates around the cylinder block, around the cylinder liners and upward through the cylinder heads (4).
The coolant flows from the cylinder heads, through elbows (2) to the exhaust manifold shields (3). The coolant circulates through the exhaust manifold shield and forward to the temperature regulator housings (6) at the front of each exhaust manifold.
FLOW OF COOLANT (D399 Illustrated)
1-Aftercooler. 2-Elbow. 3-Exhaust manifold shields. 4-Cylinder head. 6-Temperature regulator housing. 7-Expansion tank. 9-Flywheel housing. 10-Cylinder block. 11-Oil cooler. 12-Water pump. 13-Inlet pipe.
Regulators, positioned in each regulator housing, control the flow of coolant to the heat exchanger (15) to regulate the temperature of the engine coolant. The regulator housings are connected by a crossover tube. The coolant flows through the heat exchanger to the expansion tank (7). The inlet pipe (13) of the water pump is connected to the expansion tank.
A bypass line (5) extends from the inlet side of the temperature regulator housing to the inlet side of the water pump. When the temperature of the coolant is not high enough to open the regulators, coolant bypasses the heat exchanger to assure quick warm-ups. A portion of the coolant flows through the bypass line at all times.
Raw Water System
Raw water is pumped by raw water pump (14) to the raw water connection elbow (16) at the raw water aftercooler if so equipped. The flow is divided at the elbow and a portion directed through the front core of the aftercooler (1). The crossover pipe, on the right side of the aftercooler, directs the water through the rear core. Coolant leaving the aftercooler joins with bypassed water at the elbow and then flows through the heat exchanger (15).
When equipped with a full-flow connections group, a remotely mounted raw water pump, with minimum but adequate capacity pumps raw water through the aftercooler. From the aftercooler, the raw water flows overboard. The engine-mounted raw water pump in this case and, if equipped with a fresh water aftercooler, pumps water directly to the heat exchanger.
RAW WATER FLOW
14-Raw water pump. 16-Raw water connection elbow.
Overheating
If difficulty is experienced with the engine overheating, check the following possible causes:
- 1. Coolant Level.
Insufficient coolant in the cooling system. If the coolant level has been allowed to fall so low that the coolant is no longer properly circulating, the engine should be stopped immediately and allowed to cool before adding coolant. If there is still good circulation, add make-up coolant slowly while the engine is running. These precautions will minimize the possibility of cracking the cylinder heads.
- 2. Raw Water.
Insufficient raw water. Excessive scale or sediment deposits in the inlet and outlet lines will reduce the amount of raw water available to cool the engine coolant. Partially closed valves will also restrict the flow of raw water to the heat exchanger.
- 3. Water Temperature Regulators.
Failure of water temperature regulators to open. Check the regulators for opening temperature as described in the topic, TESTING TEMPERATURE REGULATORS. Observe the amount of scale deposited on the regulators. Too much scale will obstruct operation. The engine should not be operated with a regulator removed.
- 4. Water Pump.
A badly corroded, worn or loose water pump impeller.
- 5. Raw Water Pump.
A badly corroded pump body, worn or loose water pump impeller.
- 6. Internal Clogging.
Excessive scale or sediment deposits in the heat exchanger, cylinder head or block. Such deposits can cause serious damage to the engine, by retarding the transfer of heat from the head and cylinders to the coolant. In such cases, the water temperature may not be above normal. However, loose scale and sediment may deposit in water passages to such an extent that circulation will be retarded, in which case the water temperature may go above normal.
To check for lime and scale in the cooling system, remove one of the precombustion chambers and inspect the surface which comes in contact with the coolant. To remove hard scale, follow the directions in accordance with the Lubrication and Maintenance Guide.
- 7. Continuous Overload.
Operating an engine at a continuous overload, which lugs the engine speed below its rated speed, may also cause overheating. As a correction, the load should be reduced to allow the engine to operate at rated speed.
- 8. Altitude.
The altitude at which the engine is operating should be considered when overheating is encountered. The horsepower of the engine is decreased as the altitude increases. Also, the boiling point of water is lower at higher altitubes.
- 9. Water Temperature Indicator.
It may be that the indicator is not registering correctly. If the indicator is suspected of giving a false reading, install a new one and check the reading.
- 10. Overheating can also be caused by combustion gases escaping by the precombustion chamber gaskets, cylinder head gaskets, or water ferrules and seals. The gases can accumulate in the cylinder head and block, thus restricting the flow of coolant through the cooling system. Thus, the coolant temperature rises rapidly and hot spots will exist in the cylinder head. The easiest method of checking for this condition is to carefully remove the filler cap and check for air bubbles. If air bubbles are present in the cooling system, check the precombustion chambers for tightness and, if necessary, replace the gaskets.
- 2. Raw Water.