fieldserviceengineer
Bronze Member
Actually what happens is that as antifreeze ages from heating cycles it becomes acidic. Combined with additive precipitation such as silicate additives found in LD auto antifreeze which will fall out of solution especially when the coolant pH gets down to less than 8.0 pH, thus a form of sludge accumulates in the bottom of the water jacket where coolant flow is much less turbulent. It settles there allowing the acidic sludge to corrode and rust the freeze (core) plugs. When they show signs of coolant leakage such as a crystalline deposit or dampness associated with coolant leakage, replace all the plugs not just the one. While all are removed use a garden hose to wash the lower end of the cylinder block and you may need to physically break up this gelled sludge as well. Replace the plugs then flush the engine with a two part powdered acid/alkaline cooling system flush such as Prestone manufacturers. Follow their instructions carefully. Failure to do so may result in the system being left in an acid or alkaline state instead of neutral.
As for "salt" the term is actually derived from the coolant additives which in dry or powder form are referred to as "salts" but not actually sodium chloride salt. Sodium silicate, sodium nitrite, sodium molybdate, sodium borate, potassium phosphate are examples of such inorganic salts used in coolant additive chemistry. These salts with the exception of sodium silicate are classified as "super soluble" meaning they dissolve readily and are very resistant to dropping out of solution (precipitation). However, sodium silicate does not enjoy such a reputation. It can be easily forced out of solution. Even coolant concentrate with silicate can have the silicate additive precipitate while still in the jug! It forms a white gel that is quite solid. Once formed is very resistant to redissolving, certainly not with anything less than the strong agitation that a water pump impeller can impart.
The good news is that the addition of new coolant to an old system does not chemically attack the old additives and cause problems. Depending on your coolant formulation and premix solution, there should be little to be concerned with in adding coolant to a low system. I do agree that just draining and refilling with new coolant without benefit of flushing is a bit of a wasted effort.
Scale formation in an engine is due to use of hard water when making coolant premix. Scale has to be chemically removed by use of strong acid flushing agents or use of chelating cleaners formulated to remove scale. Scale can not be easily removed especially not by flushing with water.
Here is a simple coolant maintenance program for diesel tractors (but can include your diesel pickup):
1. Start clean. Flush the system with a chemical cleaner following manufacturer's instructions. Do not take short cuts on this.
2. Fill the system with a 50/50 premix unless your climate dictates a 60% antifreeze/ 40% water solution (-64*F F.P.). Use premix coolant that has the necessary diesel cavitation protection chemistry already added. You may add it yourself as you make the premix coolant solution.
3. A good target nitrite content is 2000 - 2400 PPM nitrite. Use a test strip to determine that. Or use Fleetguard DCA4 liquid at 6.5 ounces per gallon of premix.
4. Whenever the system is low, use the same coolant mix you filled with or one that is chemically similar. Meaning: the color can be different but the amount of glycol/water should be 50/50 if that is what you started with. The additive chemistry should be mixed at the same rate as when doing the first fill.
5. Test with test strips at least twice yearly if you only put on a few hundred hours of operation each year (season).
6. Properly mixed/formulated coolant with this maintenance will last for up to 5 years of operation assuming you can put on 2000 hours of operation. Coolant has a lot longer life when properly maintained than what the OAT coolant manufacturers want you to believe so that you will buy OAT to get "long life".
