All of these are valid reasons to keep a piece of “experienced” iron around, but when it comes to repairs as opposed to rebuilds, the water gets a bit muddier.
Recently on a Facebook discussion (yes, social media has found rural America), a friend had an older tractor that was putting coolant into the oil, causing the milky-looking combination we all loathe. He pulled the head and found no cracks, but as he dug further, he found pinholes in his No. 5 cylinder sleeve.
His question to the group was, “Since the rest of the cylinders appeared to be sound, could he simply replace the one sleeve and piston?” Cost was a factor, but as the conversation went forward some powerful arguments against a quick fix surfaced. The cause of the issue was obvious, however: cavitation.
Cavitation occurs in wet-sleeved diesel engines, beginning as combustion forces set up a natural vibration in the sleeves. This causes the sleeve walls to first pull rapidly away from the coolant, creating an area of low pressure. In this low-pressure area, the surrounding coolant boils and forms tiny air bubbles.
As the sleeve springs back, it connects with the bubbles (with a force estimated up to 60,000 psi), causing the bubbles to implode against the sleeve, pitting it or causing “cavities.”
As these cavities occur, they create opportunities for more cavitation, and the repeated process eventually drills the sleeve, causing a leak. Adding to the issue, coolant is not compressible, so as it contaminates the cylinder, it puts tremendous pressure on the other internal components, and the result is a cracked block, damaged pistons or bent connecting rods.
The key to preventing cavitation is good chemistry in your coolant system. A good coolant contains cavitation-resistant native oxides that create a film on the sleeve’s outer wall. These properties can break down over time, so it is wise to have your coolant checked or changed out from time to time. Most experts recommend a two-year interval change depending on load and use conditions.
Walter Moore, editor of Construction Equipment magazine, shares these thoughts on coolants. For many coolants, a supplemental coolant additive (SCA) package not only has compounds that help the cooling system resist corrosion, scaling and attack by acids, but also contains nitrite, which mends the sleeve’s protective-oxide film when cavitation tries to wear it away.
Some SCA packages also contain molybdate, intended to enhance nitrite’s healing action and thus allow lower levels of nitrite which, in excessive concentrations, may contribute to solder corrosion.
If you still use conventional coolant, a heavy-duty, low-silicate antifreeze with an ASTM D4985 specification, then remember that this antifreeze contains no supplemental coolant additives. At initial fill, along with mixing it with 50 percent water, you must add an SCA package, typically at a ratio of 1 pint to 4 gallons of coolant.
A better alternative, says Eaton, is to use “fully formulated” antifreeze that meets ASTM D6210 specifications. These antifreezes already contain SCA components and thus require no initial treatment. In fact, all makers of vehicles with heavy-duty diesels now require coolant meeting this standard.
Moore goes on to remind us that we are the ultimate judges when it comes to our equipment. Requirements differ between manufacturers, so the best bet is to talk with your dealer and heed their advice on coolant selection, testing and replacement.
A good rule of thumb is to test your coolant freeze point in regular intervals. Sending your coolant to an analytical laboratory once a year is also a good idea. These analyses can tell you if your nitrite, freeze point and molybdate levels are in proper order. If not, an additive or a fluid change may be prescribed.
Given the changing chemistry of coolants and the increased demand placed on cooling systems by today’s engines, Bryan Debshaw, CEO of Polaris Laboratories, believes that coolant analysis will become an increasingly important tool in preventive maintenance programs.
Coolant analysis not only determines coolant condition, he says, but also identifies other vehicle problems that can show up in the cooling system. Coolant-analysis programs typically are available in various levels (and costs), depending on the number of parameters checked.
It is absolutely necessary not to buy in to the belief that extended-life coolant is maintenance-free. Check for rust, correct color (do not blend antifreezes) and use a refractometer to check freeze point.
Some conventional coolant suppliers are switching to annual flush-and-replace recommendations. Their thought is that within a year, nothing can go wrong with the coolant that would result in a catastrophic engine failure.
There are choices, maybe too many, as to which coolant to use in your equipment. At times, fully formulated conventional antifreezes and organic acid antifreezes are accidently mixed. The result is a diluted coolant where the protective properties of both antifreezes are compromised to the point of inadequate protection.
Your best bet is to select a coolant formulation that fits your needs the closest and purchase only that antifreeze to avoid cross-contamination. Then follow the coolant and equipment manufacturers’ recommendations for maintenance and replacement for the coolant you have selected. 
Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.
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Andy Overbay
- Extension Agent
- Virginia Cooperative Extension
- Email Andy Overbay
