WASHER 7M6101 - Caterpillar

3400 Family Of Truck EnginesReference: Truck Engine News, August 1987, Page 1, "Temperature Regulator Housing Parts And Water Pump Adapter Have More Resistance To Erosion And Galvanic Corrosion; Guidelines On Grounding Of Electrical Systems And Cooling System Maintenance. "Reference: "Know Your Cooling System," Form SEBD0518.Caterpillar has received reports of pitting on the cylinder blocks and liners and erosion/corrosion of the aluminum cooling system components on the 3400 Family Of Truck Engines. Investigation of these reports indicates most of the problem is the result of adverse operating conditions related to incorrect maintenance practices. By following the cooling system maintenance practices described in "Know Your Cooling System," or the Operation And Maintenance Management Guide for your engine, most cooling system problems can be prevented. Be sure to check the following items when attempting to resolve a cooling system problem.
Cooling Water Quality. Caterpillar recommends using distilled, or deionized, water to reduce the potential of inhibitor chemicals not dissolving. "Hard water," or water with high levels of calcium, magnesium and ions, increases the concentration of solids and causes the coolant to become abrasive. This can lead to the formation of scale and deposits. Coolants with excessive chlorides and sulfates will cause cooling system corrosion, particularly after a number of heating and cooling cycles. Water can be tested to find out if it is acceptable to use in a coolant mixture. See Page 9 in "Know Your Cooling System."
Antifreeze. Use 8C3684 [3.785 L (1 gal)] or 8C3686 [208.175 L (55 gal)] Diesel Engine Antifreeze. Use the correct amount, mixed with water to provide a 30% to 60% concentration. Caterpillar Antifreeze includes coolant conditioner; so do not add Caterpillar Coolant Conditioner on the initial fill - just add the conditioner to maintain 3% to 6% concentration after the first 250 hours, and each 250 hours afterward. See Page 9 in "Know Your Cooling System."
Coolant Conditioner. Corrosion inhibitors are used for the protection of metal surfaces in the cooling system. Block and cylinder liner pitting and aluminum corrosion can be controlled if the correct amount of cooling system conditioner is maintained in an acceptable coolant water or antifreeze/water mixture. The correct concentration of cooling system conditioner is 3 to 6%. Use the 8T5296 Caterpillar Coolant Conditioner Test Kit to determine the level of inhibitor concentration. See Pages 10, 11 and 12 in "Know Your Cooling System."
pH. Check the cooling system coolant's pH regularly. Do not operate an engine when the coolant is below 8.5 pH.
Grounding. If there is a bad electrical ground in the charging circuit and the ground goes through the coolant, the inhibitor can become electrically charged. When this happens, the coolant can give an indication of 8.5 to 9.5 pH and still lack inhibitor. Use the 8T5296 Caterpillar Coolant Conditioner Test Kit to avoid a false reading. Check the voltage between the battery negative post and the coolant. This check should be repeated with all the machine's electrical systems off; with the engine cranking; and with the engine and all electrical systems