21345129 Volvo.Penta Flange screw

Personal injury can result from escaping fluid under pressure.If a pressure indication is shown on the indicator, push the release valve in order to relieve pressure before removing any hose from the radiator.
Coolant
Coolant Level Check the coolant level in the cooling system. If the coolant level is low, air will be allowed to enter the cooling system. Air in the cooling system will reduce the efficiency of the cooling system. When air enters the cooling system, air bubbles form around the internal components of the engine. Air bubbles cause a reduction in the cooling of engine parts. Air bubbles can also cause cavitation of the pump during normal engine operation.Refer to Operation and Maintenance Manual, "Cooling System Coolant Level - Check".
Air Bubbles in the Coolant The purpose of a vent line is for the prevention of the formation of air pockets in the cooling system. The air pockets can form while the cooling system is filled with coolant. Air pockets will also form if the correct coolant level is not maintained. Ensure that any vent lines that are in the system are not plugged or missing.A loose hose clamp can allow air into the cooling system during the cooldown period. Ensure that the hose clamps are in good repair and ensure that the hose clamps are correctly torqued.
Quality of the Antifreeze/Coolant Solution Check the quality of the coolant. The coolant should have the following properties:
Color that is like new coolant
Odor that is like new coolant
Free from dirt, debris, and oilsIf the coolant does not have these properties, drain the cooling system and flush the system with cleaner. Refill the system with the correct mixture of water, antifreeze, and coolant conditioner. Check the radiator for a black substance that has a consistency of petroleum jelly. The contamination may be an indication of an engine that has been overheated continuously. Check for a problem with the vent line to the expansion tank. Ensure that the line is not plugged or kinked.Ensure that the cause of any contamination is investigated and ensure that any problems are corrected.Refer to Operation and Maintenance Manual, "General Coolant Information".
Coolant Conditioner and Antifreeze Concentration Check the concentration of the coolant mixture. The mixture should be approximately 50 percent water and 50 percent antifreeze with 3 to 6 percent coolant conditioner. If the concentration of antifreeze is greater than 50 percent, the ability of the cooling system to dissipate heat is reduced. Ensure that the concentration of antifreeze in the cooling system is correct. If the coolant mixture is incorrect, drain the cooling system and flush the cooling system. Refill the cooling system with the correct mixture of water, antifreeze, and coolant conditioner. Refer to Operation and Maintenance Manual, "General Coolant Information".
Cooling Fan Circuit
Fan Speed Check the fan drive system. A fan drive system that is not turning at the correct speed can cause improper air speed across the radiator core. The lack of proper air flow across the radiator core can cause the coolant not to cool to the proper temperature differential. Ensure that the fan pulley is sized correctly. Check for belt slippage. Ensure that the engine is being operated at the speed according to the design specifications for the cooling system.
Fan Improper installation of the fan can cause overheating. Ensure that the fan is installed correctly.The fan must be large enough to send air through most of the area of the radiator core. Ensure that the size of the fan and the position of the fan are according to the OEM specifications.Check that the blades of the cooling fan are not bent. A fan blade that is bent can reduce the air flow through the radiator. If a bent fan blade is discovered, straighten the fan blade or replace the fan.
Fan Shroud The fan shroud and the radiator baffling must be the proper size. The fan shroud and the radiator baffling must be positioned correctly. The fan must be positioned in the shroud correctly. The size of the fan shroud and the position of the fan shroud should meet the OEM specifications. The size of the radiator baffling and the position of the radiator baffling should meet the OEM specifications.
Drive belts A loose fan drive belt will cause a reduction in the air flow across the radiator. Check the fan drive belt for proper belt tension. Adjust the tension of the fan drive belt, if necessary.
Radiator, Hoses, and Clamps
Dirt, Debris, and Deposits in the Radiator Check the radiator for debris, for dirt, and for deposits on the inside of the radiator core. Debris, dirt, or deposits will restrict the flow of coolant through the radiator. The buildup of scale in the radiator can be caused by the use of incorrect use of cooling system additives. Deposits can be caused by the use of hard water in the system. If necessary, flush the engine cooling system and the radiator. Ensure that the correct solution of water, antifreeze, and cooling system conditioner is used in the system.Measure the temperature of the top tank of the radiator and the bottom tank of the radiator with an infrared thermometer. The temperature differential across the radiator must typically be in the range of 7 to 8° C (12 to 15 ° F). If the temperature differential is greater than this specification, the coolant flow through the radiator is not adequate. There is probably a restriction in the cooling system circuit. If the temperature differential is less than this specification, the coolant flow through the radiator is too great. Perform the necessary repairs in order to correct these problems.Check the fins of the radiator core for debris or for damage. Debris and damage to the fins of the radiator core will restrict air flow through the radiator core. An overheating problem can develop. Perform the necessary repairs.Refer to Testing and Adjusting, "Cooling System - Inspect".
Radiator Hoses and Clamps Check the hoses and clamps for the cooling system. Damaged hoses with leaks can normally be seen during a visual inspection. Hoses