21246665 Volvo.Penta Hexagon screw

Checking Water Temperature
The water temperature gauge should normally register in the NORMAL range when operating. However, with some systems, as long as the coolant does not boil the cooling system is functioning properly. 1. Check the water temperature gauge reading frequently during operation. Note any deviation from the usual reading. Have repairs made as needed.2. If the water temperature gauge continually registers near - or in the "HOT" range - without boiling, have the gauge checked to determine if the cooling system is functioning properly. Have repairs made as needed.Checking Coolant Level
With the engine stopped:1. Slowly turn the filler cap to the first stop and release pressure.
Be careful. If the engine is warm - steam may spray outward under high pressure.
2. Push the cap down; turn until the cap is released.3. Maintain coolant level to the base of the fill pipe. 4. Make-up coolant should be one of the following, in the order of preference: a. Permanent antifreeze and fresh water solution.b. Drinkable water and rust inhibitor solution.c. Drinkable water.d. Any available fresh water.(a) Must be used if engine is to be shut down in below freezing weather without draining the coolant. (b) Can only be used when the coolant temperature is above freezing, or if the coolant will be immediately drained after shut down during below freezing temperatures.(c) or (d) Should only be used as a "temporary fix". As soon as possible, return the system to either (a) or (b).Draining Radiator
If a permanent antifreeze solution is used in the cooling system, either renew the rust inhibitor every three months by adding Caterpillar Corrosion Inhibitor, or drain and replace the solution yearly.Whenever it is necessary to drain the cooling system:1. Shut off the engine.2. Slowly turn the pressure cap until the cap is released.
Be careful. If the engine is warm - steam may spray outward under high pressure.
3. Open the drain valve on the radiator. Draining Engine Jacket Water
1. Drain the radiator.2. Drain the oil cooler and water pump line. 3. Remove the engine block drain plug. Draining Marine Engine Jacket Water
1. Shut the engine off.2. Slowly turn the pressure cap to the first stop and release pressure.
Be careful. If the engine is warm-steam may spray outward under high pressure.
3. Push the cap down and turn until the cap is released. 4. Remove the water pump drain plug. 5. Remove the engine block drain plug.6. Remove the water cooled manifold drain plug. Draining Sea Water System
If ambient temperature may go below freezing, drain the sea water line between the heat exchanger and the sea water pump.1. Loosen the hose clamps and hose, or remove the drain plug if so equipped. 2. Remove the cover from the sea water pump. Filling Cooling System
When filling a cooling system, it is essential air pockets within the system are able to vent to the atmosphere. Air trapped in the system can cause major engine problems.
1. Use water that is low in scale forming minerals. Do not use softened water.2. While filling the cooling system, stop the filling procedure several times to allow the coolant level to stabilize and expel air from the system.3. Add coolant until the coolant level reaches the base of the fill pipe. Allow space for coolant expansion.4. Start the engine and allow it to idle several minutes with the filler cap off. Add coolant as necessary.5. Install the filler cap.6. Check the system for leaks. Have the engine cooling system repaired if necessary.Cleaning Cooling System
To clean the cooling system, any good commercial radiator cleaning solution can be used. Follow the instructions included with the cleaner.The cooling system can be cleaned using oxalic acid and sodium carbonate as follows: 1. Fill the cooling system with a solution of 2 pounds of oxalic acid or sodium bisulphate (NaHSO4) with every 10 gallons of water (mix 25 grams per liter of water).2. Start the engine and operate at operating temperatures for 1/2 to 1 hour.3. Stop the engine and drain the cooling system.4. Flush the system with clean water until the draining water is clear.5. Install all drain plugs.6. Fill with a solution consisting of 1/2 pound of sodium carbonate crystals (Na2CO3) with every 10 gallons of water (mix 6 grams per liter of water.)7. Start and run the engine for 10 minutes.8. Stop the engine and drain the cooling system.9. Flush the cooling system with clean water.10. Install all drain plugs.Zinc Rods
(Salt Water Operations Only)
Salt water has a highly corrosive reaction with metal by a chemical action called "electrolysis". To prevent this chemical action taking place with parts used in the sea water system, zinc plugs are placed in the sea water piping. Zinc is a relatively soft metal which reacts quite readily with the salt water. Thus, by the deterioration of the zinc, the sea water system parts are protected from corrosion.The zinc rods must be inspected regularly and be replaced as they become deteriorated. The zinc rod plugs are painted red for easy identification. Inspecting Zinc Rods
1. Move the governor control lever to the shut-off position.2. Remove and inspect all of the zinc plugs. They are painted red for easy identification. Depending upon the engine, their location may be in the oil cooler heat exchanger bonnet, sea water heat exchanger bonnet, aftercooler lines, sea water pump, or in the sea water lines. 3. Tap the zinc rods lightly with a hammer. 4. Inspect the rods. If a rod has deteriorated, or flakes apart when tapped, install a new zinc rod.Installing a New Z