GASKET-COVER 7C7955 - Caterpillar

3406 and 3408 Truck EnginesSUPPLEMENT: 04/05/78ENGINE NEWS, FEBRUARY 8, 1978, PAGES 2 AND 3.In the article "Attachment Groups Put Corrosion Inhibitor Directly Into Cooling System" there is a wrong part number in the parts chart on page 3. For "3406 Truck Engines-Turbocharged and Aftercooled", change 1N3378 Elbow to read 2N3378 Elbow.
--------------- END SUPPLEMENT ---------------SUPPLEMENT: 04/05/78ENGINE NEWS, FEBRUARY 8, 1978, PAGE 3.In the article "Attachment Groups Put Corrosion Inhibitor Directly Into Cooling System" that starts on Page 2, there is a wrong part number in the chart on Page 3. Change the first part number, 9N3367, to read 9N3366.
--------------- END SUPPLEMENT ---------------Description of Change: Some conditions of operation have been found to cause pitting (small holes in the metal surface) from corrosion or cavitation erosion (wear caused by air bubbles in the coolant) on the outer surface of the cylinder liners and the inner surface of the cylinder block next to the liners on the above engines. Correct maintenance of the cooling system can keep this type of damage at a minimum. To give the cylinder block and liner surfaces maximum protection, a 3% to 6% concentration of liquid corrosion inhibitor, or .8 to 3.4 ounces of a dry inhibitor per gallon of coolant, must be present in the cooling system at all times.
Owners can now get this type of corrosion protection for some of their engines from an attachment group. The elements used in these groups have a specific amount of inhibitor for acceptable cooling system protection. As water or coolant flows through the element, the corrosion inhibitor, which is a dry material, dissolves (goes into a solution) and mixes with the water or coolant to the correct amount of concentration.
When a cooling system is first filled with new coolant or water, an element with larger than normal amount of inhibitor (precharge) is used. At the first oil change interval, the precharge element is removed and an element with a normal amount of inhibitor (maintenance) is then installed to keep the corrosion protection at an acceptable level. After the first change period, only maintenance elements are installed to keep the cooling system protection needed. Use the chart that follows to find the correct precharge and maintenance element to be used.
The service life of a coolant conditioner element is based upon a 10,000-12,000 mile (16,100-19,300 km) change interval and an expected coolant life of 100,000 miles (161,000 km) or one year.
Any extension of the element change period beyond the 10,000-12,000 mile recommendation can result in the loss of adequate cooling system protection.
Adaptable To: While the groups are not available for parts service as groups, the separate parts can be ordered and installed according to the instructions given in Special Instruction Form SEHS7222. Installation instructions given are for the remote mount groups. The groups are adaptable to 3406 and 3408 Truck Engines as shown in the chart that follows: If water must be added to the cooling systen on a daily basis, either the cooling system has a leak or