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.
IMPROVED PERFORMANCE
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.
SYSTEM MAINTENANCE
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:
- Properly maintain an aluminum system.
- 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.
THE RIGHT COOLANT
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.
TWO YEAR VS. FIVE YEAR
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.
ACID OR ALKALI
Incorrect pH levels (too acidic or too alkali) will accelerate cooling system corrosion. Aluminum components will pit and flake. These flakes will then enter the coolant solution, remaining in suspension until they reach a “cooler” area (like the bottom of a radiator or heater core) where they will drop out of solution and build up until the system is clogged. This phenomenon is know as transport depositing and is deadly to an aluminum system.
ELECTROLYSIS
If electrolysis is the problem, it must be corrected before any replacement parts are installed. If there is excess voltage in the system, the coolant becomes an electrolyte and galvanic action leading to premature failure occurs. The aluminum component, which comes in contact with the charged coolant will be oxidized and coolant loss will eventually result when the material is sufficiently corroded.
The most common form of corrosion failure is the formation of pinholes in the inlet or outlet tanks or connections of aluminum radiators and heaters. In addition, electrolysis will alter pH levels, accelerating corrosion. If electrolysis is detected and confirmed, the source of the excess voltage must be located and corrected. The starter, alternator and radiator cooling fan(s) are prime candidates for producing stray electrical charge due to missing or inadequate grounds. But if the suspect is a different component or accessory you will have to isolate the problem circuit(s). Begin by removing and replacing one fuse at a time from each circuit while noting the voltage reading. When you record a voltage drop, you have found your problem circuit. Repair the circuit and then check the system again. For other electrical accessories, you may have to operate them one at a time, again noting the voltage readings. Never try to short cut the remedy by just adding extra ground straps as this may only exacerbate the problem.
Many newer systems have flow restrictors to limit the speed at which the coolant moves through the system. This is done for two reasons. The first is to allow more complete heat transfer from the components to the coolant. The second is to protect the thin gaseous film mentioned earlier. It can be washed away due to acceleration of the coolant moving through the system. In addition debris or other contaminates in the system can also “brush” away this protective layer. This is why cooling system maintenance, especially for aluminum systems, must be performed on a regular basis.
ALUMINUM REPAIR
When first introduced, aluminum radiators with their plastic tanks were thought to be unrepairable. In fact, many cooling system professionals considered aluminum radiators as “throw away” units. Today’s cooling system professional must be able to repair plastic tank aluminum radiators as efficiently and profitably as he has been able to with their copper/brass predecessors.
CLEANING OF ALUMINUM RADIATORS
Although aluminum radiators are extremely durable, they can still become blocked. The cleaning of aluminum radiators at first presented challenges to the cooling system professional. The first benchman to place an aluminum radiator in the boil-out tank got a nasty surprise. When aluminum comes into contact with the caustic chemicals in a boil-out tank, the reaction is a violent collision of chemicals. In other words, the boil-out tank and the ultra-sonic cleaners we use on CBRs are no longer an option. Aluminum radiators are effectively cleaned using speciality chemicals that are designed to work with the aluminum composition. In addition, a good careful rodding out will handle most obstructions.
DAMAGE REPAIR
Damaged tubes and fins no longer have to mean a trip to the junk pile for an aluminum radiator. Minor core damage is repairable. With the advent of specialized welding (MIG) and the development of epoxies, solders and welding rods, the professional can repair most if not all damaged aluminum cores. In addition, even if there is major damage, cores can be replaced.
CORE REPLACEMENT
With the correct training and the right equipment the aluminum core can be replaced. As aluminum radiators age and systems deteriorate, more and more aftermarket parts are becoming available. This proliferation of replacement parts has given the radiator professional options never before thought available when recoring aluminum radiators. Replacement cores are now available in both the aluminum OEM replacement and a copper/brass core that can be fitted up to the plastic tanks. This is an advantage for the shop that longs for the CBR days. With over 1400 part numbers available, recoring of aluminum radiators is becoming as common as recore of CBRs.
While aluminum radiators are susceptible to leaks at the joints between tube and header or at the end tubes, the most common failure is a leak occurring at the gasket joint between the header and the plastic tank. This has proven to be the weakest link in a plastic tank aluminum radiator. But this has also proven to be a profitable repair for the radiator shop. Removing the radiator, taking off the tank in a special fixture, and replacing the gasket is a low-cost job. The advent of easy to use epoxies have made the process even easier. With practice, a good benchman can perform this procedure in under an hour. If the tank itself is damaged, replacements are readily available from any one of a number of supply houses. Many shops remove radiators from collision damaged vehicles to scavenge the tanks. These are then held is stock for replacement purposes. A small inventory can save a lot of time and headaches.
Today’s modern cooling systems must be serviced at regular intervals and kept within specs in order to function properly and avoid breakdown or premature component failures. By the middle of 1999, the majority of vehicles produced in the United States were using organic acid coolants. These coolants, while allowing for greater heat transfer, better protection and extended replacement intervals, must be regularly checked to insure proper protection ability. When facing the replacement of a failed component, do a complete inspection and get all information about the system possible. The time and money you save will be yours. By being thorough in your diagnosis, you will be able to perform complete and accurate repairs.
Source: Radiator.com. Volume 14, No. 3. May/June 2000
http://www.radiator.com/articles/alumrads.html