While both mystery and controversy surround the situation, you can no longer order Cummins Engine Co. power with a factory fill of “long-life” coolant. The only such product used for this purpose-over the last four years-was Texaco Extended Life Coolant, known as “TELC.” But it’s now claimed by Cummins to have caused coolant loss in some engines by damaging the silicone used in rocker-cover gaskets and other seals. The extent of the problem is unclear, but it may be that only a small number of factory-filled engines have been affected-3% in the case of the huge Florida-based Ryder Transportation Service fleet, and all of those were N14s with rocker-box problems.

The lubricant division of Equilon Enterprises, the U.S. joint venture between Texaco and Shell Oil, denies that TELC is responsible, and also says that only N14 engines are affected. It notes that no other engine maker has reported a problem. In fact, it held a press conference at the Great American Truck Show in Dallas last month, during which representatives of Caterpillar, General Motors, and Ryder described their trouble-free use of TELC. Supportive letters from Detroit Diesel, Mack, and Navistar were also read to the press.

TELC contains organic-acid additives, called “carboxylates,” and nitrates. These organic inhibitors deplete very slowly, eliminating the need to add supplemental coolant additives (SCAs). At two years or 3000 hours, a specific “TELC extender” is added, giving another two years or 3000 hours of life. The coolant is claimed to provide high-temperature aluminum protection and to prolong water-pump life. Used in highway diesels for the last four years, TELC is also marketed by Caterpillar as Cat Extended Life Coolant, by Shell as Rotella Extended Life Coolant, and by Detroit Diesel as Power Cool Plus.

A late-June letter from Cummins to truck OEMs and distributors stated: “…based on available data, Texaco’s Extended Life Coolant and other similar formulations supplied by Equilon Enterprises … should not be used in Cummins engines.

“These organic-acid coolants appear to cause degradation of the silicone seals after 80,000 to 100,000 miles.”

The engine maker says these coolants cause silicone seals to shrink, harden, and crack. The rate of degradation depends on the temperature and time of exposure to the coolant. Water-pump seal life and coolant loss through “coolant creep” around seal and hose connections are other issues, it says. All Cummins engines have one or more silicone cooling-system seals.

What should you do? Cummins initially recommended that ELC coolant in existing engines be drained and replaced with conventional coolant. But more recently the company said that “may not be necessary or helpful at this time” because it won’t remedy the situation. It has continued to ask truck manufacturers to halt TELC factory fills.

Cummins specifically recommends using traditional, fully formulated coolants that meet TMC (The Maintenance Council) Recommended Practices RP 329 and RP 330, or ASTM specifications D6210 and D6211.

There’s no easy way to tell what antifreeze is in your engine because no color standards have been developed for the different coolants. TELC is red, incidentally, which may help drivers on the road who need to top up. But beware: TMC’s RP338 says that if more than 10% of conventional coolant is added to a system filled with ELC, the second coolant cancels out the benefits of the primary fill. The entire system must be drained.

Equilon has continued to recommend the use of its long-life coolants, naturally enough, though not in N14s. However, in a joint statement released in August by Texaco and Cummins, the coolant maker agreed with Cummins that only conventional coolants should be used as factory fills until a solution is found.

Ryder’s senior maintenance manager, Art Trahan, says TELC “remains the only approved coolant for use in all Ryder-maintained vehicles.” He added that Ryder continues to ask all truck makers to provide TELC as a factory fill.

If you have Cummins power, contact Cummins or your truck manufacturer for more information. Even if you use other engine makes, check with those manufacturers. In the meantime, both Cummins and Equilon are looking for answers.