Few automotive systems have so simple a primary function: keep the engine from melting down. Cooling systems, however, have become an integral part of auto emission control systems and overall cabin temperature control, making service more than a pressure test and temperature check. And new technologies on the horizon promise to add computer control to coolant flow, offering faster warm-up and even lower emissions. The scan tool may emerge as the primary tool for cooling system diagnosis.
What’s coming: more precise control
Future automotive cooling systems will be expected to play their part in fuel economy and emissions performance, meaning more complexity and computer control. Visteon’s PrecisionCooling system is an example of a “smart” system that may be coming to your bays soon.
PrecisionCooling improves fuel economy up to five percent, reduces hydrocarbons without increasing nitrogen oxides (NOx) and carbon monoxide beyond EPA requirements, and improves heating/cooling system performance by integrating control of a vehicle’s engine cooling components into one electronic control module.
At the heart of Precision Cooling is unique software that precisely routes fluid through the engine, which improves control of engine temperature and uses fuel and heat more efficiently. This software controls operation of the variable speed fan, variable speed water pump and Visteon’s coolant control device in order to assure a more efficient system.
The system operates in three modes: start-up, economy/cruise and power/acceleration. The electronic control module continually monitors the vehicle operating conditions and, as required, transitions from one mode to the next.
Start-Up is used when the engine, coolant and the external environment are the same temperature. This is common after a vehicle has been parked for an extended amount of time. During ignition and warm-up, coolant is directed through the bypass circuit while minimizing pump and fan speed. This allows the temperature of the coolant and metal to increase as rapidly as possible. If a passenger requests heat at this time, the system allows flow to the heater core only when the desired coolant temperature is reached. When the coolant reaches its operating set point, it will flow to the radiator and other circuits in order to maintain the operating set point temperature.
Economy/Cruise, common during highway driving, occurs when a vehicle has reached the operating temperature and travels at a constant speed under a low load.
The system monitors vehicle and occupant inputs in order to maintain the operating temperature. When required, the system determines and adjusts fan and pump speeds in order to control coolant temperature and assure the most efficient use of auxiliary power. If a passenger requests heat, coolant will flow into the heater core. If the passenger does not request heat, the system will not allow coolant to flow into the heater core.
Power/Acceleration, common when climbing a hill or passing, is used in situations where a vehicle is exposed to high loads or quick accelerations.
Because of increased engine power output, the system recognizes an increased heat load. However, because it can forecast increased heat load, the system adjusts valve position, pump speed and fan speed before the coolant temperature increases.
Unlike conventional thermostat systems, which react after a coolant temperature increase, the ability to forecast changes helps the system maintain a more consistent operating temperature.
From a service perspective, keeping the system clean and filled with the correct coolant will likely become even more important than conventional systems. And with software controlling flow direction and rate, plus electric water pumping, extensive knowledge of electrical systems will be needed.
Installation is still an issue
For now, however, engine and cabin temperature control is still about maintaining consistent coolant temperatures by thermostat and heat exchangers (radiator/heater core). While system failures are still dominated by overheating/coolant loss/poor heat-no heat issues, component replacement requires more care than ever before. Take radiators, for example. Aluminum with nylon tanks have become the norm, and while they work well, installation practices are still an issue, declare the major component suppliers.
“Improper installation is a very common problem”, says Cindy Childerley, sales representative for the heat transfer division of SPI. “The most common reason for return is shipping damage, and number two is installation damage. Plastic tank radiators are not the same as metal; a lot of technicians are rough with them.” Childerley notes that over-tightening of mounting ears is a common mistake: “At fan mount connections, for example, I’ve seen a lot of cracked plastic.”
Careful inspection of the replacement as it comes out of the box is always a good idea, not only for damage, but also for missing parts. Small things make a surprising amount of difference. Captive “speed nuts”, for example, are a fast and secure method of radiator or rad shroud mounting, but they’re more than quick and cheap. They also spread clamping loads over a larger surface area of plastic, so if a technician substitutes a nut and bolt, then over-tightens, cracks are likely. If they’re unnoticed, as is likely where the tech is in a hurry and uses an air ratchet, vibration or chafing can cause a comeback.
Another consideration is overall system performance. Why did the rad blow in the first place? If it leaks right off, it’s a manufacturing defect, which is very rare, declares Childerley. “What we look for when they come back leaking are signs of engine overheating, which is common on certain models such as the ’93-’97 Dodge Caravan, where there are obvious signs of head gasket leaking. Another problem that’s growing in importance is electrolysis, which is caused by poor grounding. It’s seen commonly at hose connections, where a hole is eaten through the aluminum. The electrical current goes right through the coolant. Checking of grounds should be part of every cooling system inspection.” Todd Sadeghian, regional sales manager for Visteon Canada Aftermarket Climate Control Systems agrees: “Electrolysis is still a problem we see a lot of with heater cores. It’s something that has to be addressed at the installer level.”
Inside the pipes
Containing the working fluid takes careful component installation, but what about the coolant itself? There is a surprising amount of misinformation in the industry about coolant/antifreeze and its various types.
Ethylene glycol-based coolant is the original product, but is available in two basic formulations, conventional and long-life. “Long life” is a relative term, but there are differences in formulation between it and conventional products. Mention “long life” and most technicians think of “Dexcool”, a GM trademark that’s still causing confusion in the market over five years after its introduction. According to Gord Robertson, vice-president of business development for Honeywell’s Consumer Products Group (Prestone): “Typical antifreeze has been ethylene glycol-based for years. Today there are different kinds of coolant. Ten years ago, the car companies challenged the coolant manufacturers to make the product last longer. We wanted warranties to outlast our competitors; different companies responded in different ways. GM followed through on long life development and made long life coolants a requirement for their new cars.”
Dexcool was the result; a brand name that specifies long-life coolants that have been approved to General Motor’s extended life standard. Prestone and Texaco manufacture current brands of Dexcool product.
OEM approval for specific standards like Dexcool is very expensive, and as a result, many long-life products don’t carry the label. That doesn’t necessarily mean that they’re inferior, however, declares Robertson: “Other firms have long life anti-freeze, but they can’t be called Dexcool. They may or may not meet the Dexcool performance standards. “Long
life” is a generic term.” If your customer drives a GM vehicle, however, Robertson notes that Dexcool approved product preserves the vehicle’s warranty and is a guarantee of performance.
There are many more coolant technologies, including propylene vs. ethylene glycol types, “diesel” formulations and inhibitor additive packages for recycled product. Check out next month’s SSGM for more on these and other winter chemical product issues.