Usage:
Caterpillar Diesel Engines With Jacket Water Aftercooling
- SUPPLEMENT: 10/23/92
Service Magazine; August 31, 1992; Page 7; "Supplemental Coolant Additive Requirements" for Caterpillar diesel engines with jacket water aftercooling.
Restrict the use of information in this article to specific applications. Make reference to the article with the same title in this issue for coolant requirements.
--------------- END SUPPLEMENT ---------------
Engine coolant mixtures generally consist of water, antifreeze, and supplemental coolant additive (SCA), or water and SCA only with no antifreeze. SCA is also called coolant conditioner or inhibitor.
Water is the most efficient heat transfer agent and is universally available. Distilled or deionized water is recommended to minimize any contaminants which occur naturally in water. Antifreeze is added to the mixture to lower the freezing point of the coolant. Supplemental coolant additive is necessary to overcome the qualities of the water that can cause cooling system corrosion.
In applications where operating conditions do not require freeze protection (antifreeze), a coolant mixture of water and SCA is adequate to cool and protect engine components.
The amount of SCA must be increased for the initial pre-charge when using a coolant mixture without anti-freeze. The recommended concentration of liquid SCA for water-only coolant is 6 to 8%. The additional volume of water requires an increased percentage of SCA. Normally, with a water and antifreeze mixture, only 3 to 6% SCA is required.
Maintenance of the 6 to 8% SCA concentration in water-only coolant is the same as maintenance for the 3 to 6% SCA concentration in a water and antifreeze coolant mixture. Refer to the appropriate Operation and Maintenance Manual. Due to the greater volume of water in the water-only coolant, the coolant saturation capability has been increased. The recommended change interval for a water, antifreeze, and SCA mixture is 3000 hours. It may be possible for the coolant change interval, for a water and SCA mixture, to be extended. See the appropriate Operation and Maintenance Manual for flush and fill recommendations for water-only cooling systems.
NOTE: Water-only coolant is NOT recommended for diesel engines with Air To Air After Cooling (ATAAC). ATAAC engine require a minimum of 30% antifreeze in the coolant mixture to prevent water pump cavitation. (The antifreeze in the coolant increases the boiling point of the coolant mixture.)
Procedure To Measure The SCA In Water-Only Coolant Mixture
The 8T5296 Conditioner Test Kit can be used to evaluate the SCA concentration in a water-only coolant mixture with the following modifications to the test procedure. The test procedure, as defined on the card enclosed with the test kit, must be modified as follows.
NOTE: The information in italics is the modifications to the test procedure on the card.
Test Procedure:
1. Fill the dropper pipet to the 1.0 mL mark with the coolant to be tested.
2. Dispense the 1.0 mL coolant sample from the dropper pipet into the empty vial. (Be sure the vial is clean.)
3. Add tap water to the vial up to the 20 mL mark. A 20 mL mark IS defined on the vial. (It is on the right side of vial when looking at the normal 10 mL fill level marking.) Replace the vial cap and shake. Now pour out the mixture until 10 mL remains in the bottle. Use the dropper pipet as an aid to remove liquid to the 10 mL level.
4. Add 2 or 3 drops of red SOLUTION B to the vial and swirl to mix.
5. Add 1 drop of orange SOLUTION A to the vial and swirl the mix. Continue this procedure of adding 1 drop of SOLUTION A and swirling until the mixture in the vial changes color from red to pale gray, green, or blue. Record the number of drops of SOLUTION A required to cause the color change. With the defined procedure, the 6 to 8% SCA concentration will produce a 20 to 27 drop range. Less drops indicates an under concentration of SCA and more drops indicates an over concentration. Adjust the SCA concentration until the test produces a color change in the 20 to 27 drop range.
NOTE: For more consistent results in the number of drops required to get the color change, hold the SOLUTION A bottle vertically over the vial as the drops are added. This bottle position will provide a more consistent drop size and thus will provide better test results.