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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.
NARSA Service Reports (NSR) is the official technical publication of the National Automotive Radiator Service Association, Inc., P.O. Box 97, East Greenville, PA 18041. The material published in NSRexpresses the views of contributors and not necessarily that of NARSA. Every attempt has been made to ensure the accuracy of the content of NSR.NARSA, however, will not be responsible for the accuracy of the information published nor will NARSA be liable in any way for injury, labor, parts or other expenses resulting from the use of the information appearing in NSR.
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