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 Aluminum Cooling System: A Benefit or a Headache?
Narsa System Reports
Volume 14, No. 3 May/June 2000

Aluminum is rapidly becoming the material of choice for almost all cooling system applications

Aluminum cooling systems are now part of almost every new vehicle manufactured around the world. Does this technology fit your shop technician’s ability, or does it just give them (and you) fits? The automobile industry has been slowly introducing aluminum into the cooling system for years. In the last five years, all-aluminum systems have become almost standard. We are referring to the cooling system and its components (vehicle manufacturers have been using aluminum in engine design since the late fifties) and not the engine or, more specifically, the cylinder head design. Although the cylinder heads can be considered part of the cooling system, we are focusing on the primary components in the cooling system and those most susceptible to failure, the radiator and heater core.

Aluminum radiators and heater cores allow for greater heat transfer ability using the same or less space required for traditional copper/brass components. This is an obvious benefit as vehicle manufacturers are trimming weight in order to increase fuel efficiency while at the same time running engines hotter to decrease tailpipe emissions. But with this benefit come common headaches due to the fact that aluminum components require more detailed attention than their copper/brass counterparts.

The failure to properly maintain an aluminum system can lead to premature, sometimes catastrophic failures of the radiator and/or heater core. This service report is written in order to help the installer perform two vital functions:
  1. Properly maintain an aluminum system.
  2. Recognize and diagnose the symptoms of aluminum system failure.

The majority of aluminum cooling systems have been designed to operate utilizing organic coolants. These extended-life coolants are less toxic to humans than their ethylene or propylene glycol brethren, but their extended (5/150) life span allows for the consumer to ignore their cooling system for an extended period of time. This is where the cooling system professional comes into play. The consumer must be educated as to the importance of properly maintaining their aluminum system. It is not good practice to wait the 5/150 life of the coolant. Rather, they should have the system checked every 2 years or 24,000 miles and serviced within the time frame of the coolant life if no adverse conditions present themselves earlier. In addition, anti-freeze containing carboxylate or similar organic acid technology (OAT) cannot be mixed with conventional anti-freeze (ethylene or propylene glycol based).

The OAT anti-freeze is designed specifically for the protection of the aluminum system. It provides a microscopic barrier, a thin gaseous film, as protection for the system components. This film “bonds” to the aluminum surfaces it comes in contact with, providing protection against corrosion. When conventional anti-freeze is introduced into the system, this protection is washed away and chemical reaction corrosion begins almost immediately. Remember that the use of long life anti-freeze as a replacement for conventional anti-freeze does not extend the recommended system service requirements as set forth by the manufacturer. The “extended” life or protection ability of the long life coolants only applies to new vehicles in which the coolant is installed initially and then maintained by regular system service.

Coolant conditions (level and color) are the first checks. Just because it’s orange doesn’t mean it’s clean. Vehicles using organic technology coolant must not be allowed to operate with low coolant levels. Proper coolant levels are vital to aluminum systems to provide cleaning abilities. Low coolant levels may allow suspended contaminants to drop out of solution and clog the system causing overheating.

The first step is to check the solution with an anti-freeze tester for proper freezeup, boil-over protection. Many major automobile manufacturers now recommend the use of a refractometer when testing antifreeze. The use of this tool presents the technician with a more complete picture of the coolant’s condition.

Next check the pH level. This can be accomplished using a simple pool and spa test kit or pH test strips which can be obtained at any swimming pool supply dealer. When performing this test, keep in mind that any reading between 7.7 and 9.3 total pH is within manufacturers’ guidelines and is therefore acceptable.

Using a multi-meter, check the system for electrolysis. Turn the dial on the meter to DC volts, touch the negative lead to the negative battery post and dip the positive lead into the coolant at the filler neck. Take care not to touch the bottom of the tank or the sides of the filler neck. Any reading over .01 volts indicates excessive voltage in the system. Check the system with the engine off and then again when starting and running the engine. Many electrolysis failures are caused by poor starter grounds, so it is important to turn the engine over at least once during this test.

If the coolant solution fails any of the tests or you have any suspicions regarding its quality, a complete flush and fill is recommended. The use of a flushing machine is recommended to perform this service. If a flush machine is not available, the most advisable method is three (3) complete flush cycles. Drain the system, refill with water and run the engine up to operating temperature. Shut the vehicle off, letting it cool to the point that it can be safely drained. Refill the system with water and then repeat the process two (2) more times. When the flushing is complete, refill the system using the manufacturer’s recommended anti-freeze. NEVER re-use old anti-freeze, regardless of its condition or color.

Bear in mind that conventional antifreeze chemistry (ethylene or propylene glycol) will override OAT anti-freeze chemistry, converting the system from a five-year service cycle to a two-year cycle. In addition, the same is true for systems containing OAT technology coolant that have been topped up using conventional coolant(s). Create your coolant solution by making a 50/50 mix of anti-freeze and water. DO NOT exceed a 65% anti-freeze to water ratio as this may cause silicates and/or additives to drop out of solution, clogging the system you just cleaned. Once the system is filled, start the engine, run it up to operating temperature making sure that any excess air escapes the system. Allow the system to cool, check for proper coolant level and look for any leaks.

What do you do when you are faced with a suspected or obvious cooling system problem or failure? The first and most important step is to perform a complete diagnosis of the problem. Collect as much information about the trouble, when and how it started, driving style and habits and any other pertinent information. Find out if this is the original coolant or whether it’s been replaced. What is the condition of the coolant? Check the pH level, check for electrolysis, and look for residue around the filler neck. What is the color of the coolant? Performing a complete system inspection will allow you to get to the heart of the problem, correcting the cause and not just curing the symptom and preventing a possible comeback.

The major causes of failures in aluminum systems are abuse and neglect and electrolysis/pH problems. Once you have located the failed part and determined the cause(s) of the failure, there are several steps you must take first before replacing the failed part.

If the problem is abuse or neglect (both of which will most likely provide you with electrolysis/pH problems), you must recognize the importance of proper maintenance of the cooling system. If the problem was a pH problem, you must find the cause of the imbalance in the solution. Has the system been topped off or refilled with bad coolant? When was the last time the system was serviced and by whom.

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