In 1984, the Maintenance Council (TMC) of the American Trucking Associations, Alexandria, Va., formed the Tomorrows Truck Task Force. This group took on the chore of consulting with truck and component builders to make sure that the equipment of the future would meet the needs of our industry.
The group put together several Society of Automotive Engineers (SAE) papers on the subject-the last one published in 1993. Since the beginning, the Task Force has asked manufacturers to make vehicles and components less reliant on periodic maintenance. Almost all systems on a truck got a mention, including the cooling system.
It seems that maintenance people are not fond of testing supplemental coolant additive (SCA) concentrations at each preventive maintenance interval. And theyre even less fond of costly engine repairs that result from their failure to get the complicated chemical balance just right.
The industry has made great strides in many areas. Transmissions and differentials used to need fluid changes at 50,000 mile intervals. Today, with proper fluid selection, that number is 250,000 miles or more. And the engine makers are now comfortable with recommendations of 25,000 miles or more between oil changes.
At a 1993 SAE meeting, Chuck Blake of Detroit Diesel presented a manufacturers response to the Tomorrows Truck paper. He admitted that the cooling system was one area that engine makers were still struggling with. But since then, even the cooling system has become less reliant on maintenance.
Some of the coolant filters available today release additives only as needed. This means that they can keep the SCA concentration within acceptable levels for a longer time. Extended-life coolants (ELC) now available can go for 300,000 miles without service. At that point they require the addition of only one can of extender.
Classic Express Inc., of Cleveland, Tenn., has already converted most of their trucks to Texaco Extended Life Coolant. They did this to reduce the cost of maintenance and to keep the trucks on the road. Heres how they do it.
A straight flush
David Dunn, one of four technicians employed at Classic Express, gave us the rundown on their coolant flush and conversion procedure.
Before starting any cooling system service you should let the engine cool. If the system is in good condition, it can hold up to 15 psi when it is hot. That pressure helps to prevent boiling of the coolant, so opening the cap on a hot system may cause the coolant to instantly start boiling. Severe burns can result.
The Texaco procedure calls for a check of all cooling system components. Theres no sense in flushing a system and installing new coolant if the system is leaking. If a water pump is weeping, now is a good time to replace it. A check of all hoses and clamps is also in order.
Once he is sure he has a candidate for conversion to ELC Dunn drains the old coolant from the radiator and engine.
Most of the engines are Detroit Diesel Series 60s, and the first place everybody goes to drain the coolant on these engines is the lower radiator hose. While opening the drain on the lower hose gets most of the coolant out of the system, there still are a few gallons trapped in coolers and heater cores. So before flushing the system, Dunn takes the time to open the drain on the passenger side of the engine block. Also on the passenger side is the oil cooler, so he drains that next. Finally, he drains the heater cores for the cab and sleeper. Those are best drained by removing the hoses.
At this point, Texaco says to close the coolant filter shut-off valve. Since no regular SCA treatments are used with their coolant, they recommend taking the valve out the filter and installing a blank (zero-chemical) filter. Classic Express takes it one step further by removing the filter completely.
Dunn takes the hoses off the filter housing, and removes the housing and brackets. He then follows the hoses back up to the engine and removes the hoses and pipe fittings. Pipe plugs block off the openings and eliminate a potential source of leaks.
With the coolant filter out of the way, Dunn checks the old coolant for contamination. If there are any signs of engine oil or other contaminants in the drained coolant, the system gets flushed with a cleaning solution. In most cases, the old coolant looks and smells fine, so he fills the engine and radiator with straight water. According to Thomas Womac, co-owner of Classic Express and Dunns employer, the shop uses municipal water, and quality isnt a problem. Even though this water isnt staying in the engine, you might want to think about alternative water sources if your main water supply is a well with extremely hard water.
Dunn runs the engine for about 30 minutes with straight water in the system. He works in a heated shop, so the thermostats open and the water circulates completely. Texacos procedure says to keep the engine temperature over 160
