3208 Marine Engine General Coolant Information Caterpillar

General Coolant Information
1.1. Water
2.1. Additives
3.1. Glycol


Never add coolant to an overheated engine. Engine damage could result. Allow the engine to cool first.


If the engine is to be stored in, or shipped to an area with below freezing temperatures, the cooling system must be either protected to the lowest outside temperature or drained completely to prevent damage.


Frequently check the specific gravity of the coolant for proper freeze protection or for anti-boil protection.

Clean the cooling system for the following reasons:

  • Contamination of the cooling system

  • Overheating of the engine

  • Foaming of the coolant

Note: Air pockets can form in the cooling system if the cooling system is filled at a rate that is greater than 20 L (5 US gal) per minute.

After you drain the cooling system and after you refill the cooling system, operate the engine. Operate the engine without the filler cap until the coolant reaches normal operating temperature and the coolant level stabilizes. Ensure that the coolant is maintained to the proper level.


Never operate an engine without water temperature regulators in the cooling system. Water temperature regulators help to maintain the engine coolant at the proper operating temperature. Cooling system problems can develop without water temperature regulators.

Refer to Special Instruction, SEBD0518, "Know Your Cooling System" and Special Instruction, SEBD0970, "Coolant and Your Engine" for more detailed information.

Many engine failures are related to the cooling system. The following problems are related to cooling system failures: overheating, leakage of the water pump, plugged radiators or heat exchangers and pitting of the cylinder liners.

These failures can be avoided with proper cooling system maintenance. Cooling system maintenance is as important as maintenance of the fuel system and the lubrication system. Quality of the coolant is as important as the quality of the fuel and the lubricating oil.

Coolant is normally composed of three elements: water, additives and glycol.



All AVSpare diesel engines equipped with air-to-air aftercooling (ATAAC) require a minimum of 30 percent glycol to prevent water pump cavitation.


Never use water alone without Supplemental Coolant Additives (SCA) or without inhibited coolant. Water alone is corrosive at engine operating temperatures. Water alone does not provide adequate protection against boiling or freezing.

Water is used in the cooling system in order to transfer heat.

Distilled water or deionized water is recommended for use in engine cooling systems.

DO NOT use the following types of water in cooling systems: hard water, softened water that has been conditioned with salt and sea water.

If distilled water or deionized water is not available, use water with the properties that are listed in Table 1.

Table 1
AVSpare Minimum Acceptable Water Requirements 
Property  Maximum Limit  ASTM Test 
Chloride (Cl)  40 mg/L (2.4 grains/US gal)  "D512", "D4327" 
Sulfate (SO4 100 mg/L (5.9 grains/US gal)  "D516" 
Total Hardness  170 mg/L (10 grains/US gal)  "D1126" 
Total Solids  340 mg/L (20 grain/US gal)  "D1888" 
Acidity  pH of 5.5 to 9.0  "D1293" 

For a water analysis, consult one of the following sources:

  • AVSpare dealer

  • Local water utility company

  • Agricultural agent

  • Independent laboratory


Additives help to protect the metal surfaces of the cooling system. A lack of coolant additives or insufficient amounts of additives enable the following conditions to occur:

  • Corrosion

  • Formation of mineral deposits

  • Rust

  • Scale

  • Pitting and erosion from cavitation of the cylinder liner

  • Foaming of the coolant

Many additives are depleted during engine operation. These additives must be replaced periodically. This can be done by adding Supplemental Coolant Additives (SCA) to Diesel Engine Antifreeze/Coolant (DEAC) or by adding ELC Extender to Extended Life Coolant (ELC).

Additives must be added at the proper concentration. Overconcentration of additives can cause the inhibitors to drop out-of-solution. The deposits can enable the following problems to occur:

  • Formation of gel compounds

  • Reduction of heat transfer

  • Leakage of the water pump seal

  • Plugging of radiators, coolers, and small passages


Glycol in the coolant helps to provide protection against the following conditions:

  • Boiling

  • Freezing

For optimum performance, AVSpare recommends a 1:1 mixture of a water/glycol solution.

Note: Use a mixture that will provide protection against the lowest ambient temperature.

Note: 100 percent pure glycol will freeze at a temperature of −23 °C (−9 °F).

Most conventional heavy-duty coolant/antifreezes use ethylene glycol. Propylene glycol may also be used. In a 1:1 mixture with water, ethylene and propylene glycol provide similar protection against freezing and boiling. See Tables 2 and 3.

Table 2
Ethylene Glycol 
Concentration  Freeze Protection  Boil Protection 
50 Percent  −36 °C (−33 °F)  106 °C (223 °F) 
60 Percent  −51 °C (−60 °F)  111 °C (232 °F) 


Do not use propylene glycol in concentrations that exceed 50 percent glycol because of propylene glycol's reduced heat transfer capability. Use ethylene glycol in conditions that require additional protection against boiling or freezing.

Table 3
Propylene Glycol 
Concentration  Freeze Protection  Boil Protection 
50 Percent  −29 °C (−20 °F)  106 °C (223 °F) 

To check the concentration of glycol, use the 1U-7298 Coolant/Battery Tester (Degree Celsius) or use the 1U-7297 Coolant/Battery Tester (Degree Fahrenheit). The testers give readings that are immediate and accurate. The testers can be used with ethylene or propylene glycol.

Information System:

3208 Marine Engine S·O·S Oil Analysis
3208 Marine Engine Fuel Recommendations
3208 Marine Engine Lubricating Grease
3208 Marine Engine Customer Assistance
793C and 793C XQ Off-Highway Truck Hydraulic System Relief Valve (Hoist Dual Stage)
3208 Marine Engine Engine Oil
3208 Marine Engine Lubricant Information
784C, 785C and 785C HAA Off-Highway Truck/Tractors Hydraulic System Position Sensor (Hoist Control)
3208 Marine Engine Hose Clamps
793C and 793C XQ Off-Highway Truck Hydraulic System Gear Pump (Hoist and Front Brake Cooling)
3208 Marine Engine Metric (ISO) Fasteners
3208 Marine Engine Standard Torque for Worm Drive Band Hose Clamps
3208 Marine Engine Coolant Recommendations
950G Wheel Loader, 962G Wheel Loader and IT62G Integrated Toolcarrier Braking System Vane Pump (Implement, Pilot and Braking)
3208 Marine Engine Conventional Coolant/Antifreeze Cooling System Maintenance
IT28G Integrated Toolcarrier Battery Disconnect Switch
3208 Marine Engine Water/Supplemental Coolant Additive (SCA)
950G Wheel Loader, 962G Wheel Loader and IT62G Integrated Toolcarrier Braking System Service Brakes
IT28G Integrated Toolcarrier Cab Air Filter - Clean/Replace
793C and 793C XQ Off-Highway Truck Hydraulic System Hoist Cylinder
3208 Marine Engine Extended Life Coolant (ELC) Cooling System Maintenance
IT28G Integrated Toolcarrier Bucket Rated Load
3208 Marine Engine Cooling System Supplemental Coolant Additive (SCA) - Test/Add
IT28G Integrated Toolcarrier Material Handling Arm Rated Load