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-Temperature regulator housing. 6-Outlet pipe. 7-Expansion tank. 8-Bypass line. 9-Flywheel housing. 10-Cylinder block. 11-Oil cooler. 12-Water pump. 13-Inlet pipe. 14-Keel cooler.
The flywheel housing has two separate passages. The upper passage carries the flow of coolant to the junction housing, at the left side of the flywheel housing. From the upper connection on the junction housing, 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 on the junction housing where it joins with the bypassed coolant from the flywheel housing upper passage.
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 with an attachment, such as a marine gear where an oil cooler is used, an adapter is mounted on the left of the flywheel housing. Part of the coolant is directed to the oil cooler from the adapter. This coolant passes through the attachment oil cooler and joins the flow of coolant in the lower passage of the flywheel housing.
In the lower passage of the flywheel housing the flow of coolant is divided to each bank of the cylinder block (10) where it circulates upward around the cylinder liners, through the cylinder block to the cylinder heads (4).
The coolant flows from the cylinder heads, through the elbows (2) to the exhaust manifold shields (3). The coolant circulates completely through the exhaust manifold shields forward to the temperature regulator housings (5) located at the front of each of the exhaust manifolds.
FLOW OF COOLANT (D399 Illustrated)
1-Aftercooler. 2-Elbow. 3-Exhaust manifold shields. 4-Cylinder head. 5-Temperature regulator housing. 6-Outlet pipe. 7-Expansion tank. 9-Flywheel housing. 10-Cylinder block. 11-Oil cooler. 12-Water pump. 13-Inlet pipe.
Regulators, positioned in each housing, control the flow of coolant. With the regulators in the closed position, the coolant passes through a bypass line (8) to the water pump.
When coolant has reached operating temperature, the regulators open. The coolant flows through the outlet pipe (6) to the keel cooler (14). The coolant then passes to the expansion tank (7) and on to the pump through the inlet pipe (13).
Overheating
If difficulty is experienced with the engine overheating, check the following possible causes:
- 1. Coolant Level.
Insufficient coolant in 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. 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.
- 3. Water Pump.
Badly corroded or worn water pump impeller or impeller loose on shaft.
- 4. Internal Clogging.
Excessive scale or sediment deposits in keel cooler, cylinder head and 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 Lubrication and Maintenance Guide.
- 5. Continuous Overload.
Operating an engine at continuous overload which lugs the engine speed below its rated speed may also cause overheating. As a correction, reduce the load to allow engine to operate at rated speed.
- 6. 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.
- 7. 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. Water Temperature Regulators.