Though long-life coolants in newer vehicles are formulated to last up to 150,000 miles or five years between changes (which ever comes first, not last), that does not mean the coolant lasts forever or never needs checking. Neglecting the cooling system is asking for trouble. The U.S. Department of Transportation says cooling system failure is the leading cause of mechanical breakdowns on the highway.
Checking the coolant level as well as its strength and condition regularly can minimize the risk of overheating and cooling system problems caused by worn-out or diluted coolant.
This is especially important on older vehicles that mostly have conventional antifreeze in their cooling systems. The coolant in these vehicles still needs to be changed every two years or 30,000 miles to replenish the corrosion inhibitors that are used up over time.
Leaks are another problem that can appear at any time, regardless of how long a particular coolant is supposed to last. Leaks are the leading cause of coolant loss, so if the coolant level is low chances are the system has a leak. Hoses, gaskets and seals can all develop leaks as they age. So too can radiators and heater cores if they are attacked from within by corrosion. Finding and fixing such leaks is a must for trouble-free driving.
Checking the coolant level requires no special tools, but you will need a coolant hydrometer or refractometer to check the concentration to make sure it provides the proper freezing and boil-over protection. Hydrometers are less expensive than refractometers, but require temperature compensation. Refractometers automatically compensate for temperature and are considered more accurate than hydrometers.
As a rule, a 50/50 mixture of either conventional or long-life ethylene glycol (EG) antifreeze and water provides boiling protection up to about 255 degrees F with a 15 psi cap, and freezing protection down to -34 degrees F. By comparison, a 50/50 mixture of propylene glycol (PG) antifreeze and water provides boiling protection to 257 degrees F and freezing protection to -26 degrees F.
Increasing the concentration of either type of antifreeze will raise the boiling protection and lower the freezing protection. Even so, the maximum concentration of antifreeze should not exceed 70% because too much antifreeze and not enough water reduces the coolant's ability to carry heat, which can actually increase the risk of overheating in a cooling system with marginal capacity.
Because EG and PG antifreezes have slightly different specific gravities (densities), you need a special hydrometer that is calibrated for PG if you encounter or install this type of coolant in a vehicle. Most refractometers have a dual scale that can read both EG and PG antifreeze.
If a visual inspection of the cooling system reveals no external coolant leaks, a pressure tester should be used to check for internal leaks. A pressure tester is nothing more than a hand pump and adapter that fits on the radiator opening. A gauge shows how much pressure is being applied to the system, and whether or not the system is holding pressure.
The cooling system should hold maximum-rated pressure for at least two minutes with no drop in the gauge reading. A loss of pressure would indicate an internal coolant leak, such as a bad head gasket, a hairline crack in a cylinder head or engine block, or possibly a leaky heater core.
The pressure tester also can be used to check the radiator cap. The spring inside the cap determines how much pressure the system holds before it vents into the coolant reservoir. The cap must provide a tight seal and allow coolant to be siphoned back into the radiator when the system cools down. If the cap fails to hold the rated pressure, it needs to be replaced. Leaky radiator caps are an often-overlooked cause of coolant loss and overheating.
Thermostats can sometimes stick open or shut, causing the engine to either run too cold or to overheat. On today's computer-controlled engines, maintaining the proper operating temperature is absolutely essential for low emissions and good fuel economy.
An infrared thermometer can be a real help here. These easy-to-use point-and-shoot devices can tell you instantly the temperature of any surface. By aiming it at the thermostat housing or upper radiator hose, you can read the temperature of the coolant as it exits the engine and tell when the thermostat is opening.
An infrared thermometer also can be used to scan the radiator for "cold spots" that would indicate an internal blockage or obstruction.
Opening the radiator drain plug and allowing the coolant to run out is not a very effective way of changing coolant. Why? Because up to half of the old coolant remains trapped inside the engine block with this method. When new coolant is added to the system, it will be diluted with all the old coolant that is still inside the engine, reducing its ability to prevent corrosion, as well as reducing its normal service life.
A much better way to change the coolant is with a coolant exchanger machine. This type of equipment typically attaches to the upper radiator hose (no cutting or splicing required) and replaces almost all of the old coolant (90 to 95%) with fresh coolant in about 15 minutes. The cycle is automatic so you can be doing something else while the unit is exchanging the coolant.
Another advantage with using a coolant exchanger instead of draining and refilling is that it eliminates air pockets that can prevent the complete refilling of the cooling system. Getting all of the air out of some cooling systems can be a real challenge, even when the system has bleeder valves for venting air. And if there are no bleeder valves, it can be even more difficult. If the system is not completely filled with coolant, the engine can overheat and boil over.
Many coolant exchangers also reverse-flush the system to dislodge sediment, rust and scale as the coolant is being replaced. This eliminates the need to flush the system with water, which takes extra time and creates additional waste and disposal issues.
Cleaning chemicals also can be used with a coolant exchanger to clean dirty cooling systems. This is done during the flush cycle to eliminate scale that builds up inside the system. Scale reduces the system's ability to transfer heat and to cool efficiently, and is a common cause of overheating.
One of the best ways to rejuvenate worn-out coolant is to recycle it. For $3,000 to $5,000, you can get a recycling unit that will filter, clean and restore the coolant to like-new condition. The obvious advantage of recycling is that it significantly reduces a shop's hazardous waste disposal problems by concentrating harmful pollutants. It also can be a profitable service because like A/C refrigerant recycling, it reduces the amount of virgin coolant you have to buy.
Recycling is also an environmentally friendly solution because it keeps ethylene glycol and heavy metals that may be picked up inside the cooling system out of the environment. Recycling has many advantages, yet of the more than 200 million gallons of antifreeze that are sold each year in the U.S., less than 15% is currently being recycled!
The U.S. Environmental Protection Agency says used antifreeze is not a hazardous waste, provided it does not contain more than 5.0 parts per million of lead. Even so, some areas have laws that restrict the disposal of used antifreeze. Recycling solves the environmental issue by keeping lead and other contaminants out of drains and sewers, while allowing a valuable resource to be reused almost indefinitely.
Ethylene glycol, the main ingredient in most antifreeze, never wears out. What does wear out are the corrosion-inhibiting additives that protect the cooling system. Nor does the coolant remain clean forever. It picks up contaminants and byproducts of corrosion. The only way to get rid of the contaminants is to replace the coolant or filter and treat it.
Coolant recycling can be done a variety of ways, but most shop recycling machines use some type of filtration process and chemical reaction to remove contaminants. The coolant is pumped though a filter (sometimes more than once), and additional chemicals (flocculants) may be added to precipitate out other impurities such as emulsified oils and heavy metals. After filtering, an additive package and dye is added to restore the antifreeze.
The effectiveness of the cleaning process can vary from one manufacturer's equipment to another, as can the quality of the additives that are used (some meet OEM specs, others may not).
Additive packages can be an issue depending on the application. The additives used in North American and Asian coolants usually differ from those used by European manufacturers. The Europeans usually specify an additive package that contains no phosphates and uses borates and low silicates. Asian vehicle manufacturers, on the other hand, use phosphates but no borates and low or no silicates.
Using an antifreeze that does not meet the OEM requirements, therefore, may void the vehicle manufacturer warranty. Even so, filling European or Asian cooling systems with a typical North American additive package (which contains silicates, phosphates and borates) should cause no problems. And once a vehicle is out of warranty, it is a non-issue.
The other way to recycle coolant is to collect it and let an outside service process it. Large scale off-site recyclers typically use reverse osmosis or distillation to separate ethylene or propylene glycol from water and contaminants. These two processes are the only ones that can remove chloride salts from the solution and deliver a virgin glycol product. It is a more time-consuming process that requires sophisticated and expensive equipment.
If you are considering buying your own coolant recycling equipment, make sure it meets your expectations as well as any applicable local regulations. California, for example, has adopted standards for recycled coolant. Other states are considering similar standards.