Why Do Good Radiators
Go Bad Quickly?
by I.M. Cool
From Mar/Apr 2000
© 2000 All Rights Reserved
Premature failure of new aluminum
1994 GM 1-ton diesel pickup
Radiator: Very popular OE replacement,
aluminum with plastic tanks, 34” X 19” crossflow
Failure: Tube seams leaking with less than two months in
Electrolysis you say? Better read on!
In the early ‘80s, carmakers began seriously switching over from copper-brass (CuBr) radiators and heaters to aluminum. As they did, they warned technicians-mechanics of potentially accelerated deterioration problems with aluminum product versus those constructed of CuBr. We were told that cooling systems and coolants “must” be maintained; if not, well, leakage will happen! Boy, were they telling the truth.
Several Cool Profit$ readers have called asking about this phenomenon in the past few years. Several articles have appeared in trade journals. It’s been the topic of discussions at numerous cooling system ed-tech sessions—and hallway gatherings—around the country. “Why in the world do brand new aluminum radiators and heaters just start leaking within as early as two weeks of installation?”
While this failure does not seem to be restricted to any specific vehicle or heat exchanger manufacturer, there is one application mentioned a lot more often than others: the 34” X 19” General Motors, plastic tank, aluminum core, cross flow radiator. But, could this just be a pure numbers thing (e.g., it’s a very popular radiator, lots of them in service, so naturally a lot of them will eventually fail)? Or, does this radiator have some special “sensitivities” that must be respected? (Hint: bet on the latter.)
This article chronicles the premature demise of one such radiator. It was an OE replacement, installed by Renschler Brothers Auto Inc., Waco, Texas that lived only two months. Its predecessor had been in place since 1994 when the truck was built. Lynn Hassell, Renschler shop foreman, called Cool Profit$ for help while the bleeding radiator still sat in the truck in one of his bays. We immediately called
Ed Eaton, President of Amalgatech, to arrange an urgent, scientific failure analysis on the still warm corpse.
What were we expecting to learn about its demise? Hopefully a scientific study would reveal whether the radiator was just plain defective as new, whether it was a victim of erosion-corrosion, or possibly, had been destroyed by electrolysis arising from stray electrical currents passing through the cooling system.
To accomplish the above tests, samples of the coolant and local tap water accompanied the radiator on its trip to the Scottsdale, Arizona lab. At this stage, nothing was ruled out.
To provide the “Who done it” of this mystery, here’s the report written—in as close to technician’s dialect as possible—by Ed Eaton. Included are the microscopic photos of the cutaway tubes plus the coolant and tap water analyses.
Ed’s Report: A Radiator Necropsy
The GM radiator submitted by Cool Profit$ Magazine is reported to be the latest in a series of premature failures experienced by the customer. It is constructed of aluminum and plastic and was removed from a
1994 diesel-powered heavy pickup.
Electrolysis? There has been the suggestion, by some members in the cooling system industry, that a group of GM pickups, exemplified by this vehicle, may be prone to cooling system component failures resulting from true electrolysis. True electrolysis occurs when stray voltage exists in the system, resulting typically from a damaged or misrouted ground connection. The stray voltage establishes a plating cell, taking metal from one metal and depositing it on another. The “donating” component is quickly, seriously and irreparably damaged. It may fail in a few days to a few months, depending on the particular circumstances (intensity of the voltage and current, the types of metal affected, etc.).
Corrosion! Most radiators sent to Amalgamated Laboratories for examination are found to have actually failed due to chemical corrosion, not electrolysis. This radiator is no exception; it exhibits the classic damage that results, sometimes quite fast, from inadequate coolant and/or improper coolant management.
The evidence. We arrived at this conclusion from evidence found in both the coolant sample provided from the coolant system at the time of failure, and the careful inspection and disassembly of the radiator itself. The radiator inspection (see photos) shows a classical corrosion of the aluminum tubes; the failure is observed at their weld seams, where most corrosion failures first appear. Electrolysis, on the other hand, would have been indicated by a surface that was clean and free of deposits and a damaged area that had a weakened, dissolved appearance. This definitely does not describe the damage done to our subject radiator.
Analyzing the test results
Photos 1 & 2
(Below) Both photos show side views of leaking tubes. Arrow points toward the tube welds. Close examination shows a hint of pinholes along the folded portion of the welded joints.
Photo 3 (Below) Shows the cross-section of a leaking tube magnified at
4 times larger than real size. The uneven pattern shows pitting of the aluminum inner surface. A “protected” tube would look shiny, flat and silver in color.
Photo 4 (Below) A close-up of the tube in Photo 3 at 40X
magnification. It clearly shows tube pitting in a pattern that demonstrates “something fell out” of
the coolant's solution, laid on the surface and started a penetrating attack. The
culprit was most like likely chlorides contained in the tap water.
Photo 5 (Below) Second tube cross-section at 4X magnification. Similar to Photo 3, but this shows large areas of
scale resembling scraping.
Photo 6 (Below) This is the second tube at 40X. The white, horizontal bands are again, scale. Scale, composed of calcium and magnesium, also comes from the Waco drinking water.
Chart 1 Below - (Click for large size) This is the test data of the analysis of the Waco city municipal water. It indicates that Waco Water is similar to other drinking water around the nation; it probably tastes good but does not make good coolant makeup water. It’s fairly high in chloride and sulfate and has a medium hardness (calcium and magnesium). Higher levels of chloride, sulfate and hardness in the water shorten the corrosion-fighting ability of the coolant.
Chart 2 This shows the Test Data from the Coolant Analysis Service performed on the coolant that was in-service during the short life of this radiator. It’s the most significant of all the data. Problems: 26% Glycol means that only half of the required coolant was in this mixture. Sure, at 26% the cooling system was still protected from freezing down to +10°F—which may keep you safe in Texas. However, without the addition of a SCA, the coolant would clearly suffer from an inadequate amount of corrosion inhibitors. Which it did!
Instead of the 9 ppm (parts per million) silicate (the element that protects aluminum) in this solution, the level should have been closer to 125 ppm*.
*Note: The original 1-gallon jug of 100% coolant contains about 250 ppm silicates. Therefore, in a 50/50 mix the vehicle’s overall silicate level should start out at 125 ppm minimum. Then of course, the silicate will immediately begin a plating (protective) action on the radiator’s aluminum surfaces. Depending on the condition of those surfaces and how much plating actually occurs, something less than 125 ppm could end up in the final solution in a fairly short period of time. Never, never, however, should it end up as low as 9 ppm!
Initially, Cool Profit$ expected to offer its readers help in understanding, identifying and diagnosing electrolysis damage as a result of this investigation. Instead, we will refocus on the importance of proper basic coolant and cooling system maintenance. This isn’t difficult, mind you; it just takes a little education, time and effort. And after all, good service is all that’s actually needed most of the time! Here are the guidelines:
• Begin with a clean system.
By the time Cool Profit$ readers are working on a system it has usually been in service for some time. Typically, at least one component has failed. It’s logical to suppose that the rest of the components in the system are worn, and that the coolant has lost its protective capabilities through aging. So be sure to completely clean out (flush with a cleaning machine (i.e. a PowerClean® type device) and check the hoses and fittings. Considering the time and effort going into a repair, a pre-emptive replacement of the radiator and heater hoses, belts, clamps, thermostat and other worn parts is a great recommendation and practice. It almost always saves the owner time, money and aggravation. Weak parts tend to fail quickly after a major repair.
• Invest in a quality, brand name coolant.
Know your coolant, your shop’s reputation is riding on its shoulders! Those marketed by the major producers, major oil companies and OEM dealers are generally reliable. Be sure they are labeled to comply with ASTM D-3306 Antifreeze Specification for cars. Trucks, even pickup trucks, benefit from the use of heavy-duty coolant. The radiator reviewed for this article might still be happily truckin’ down the road today if it had the benefit of heavy-duty coolant.
Interesting facts: When this truck, a 1994 GM pickup, was manufactured, the coolant used to fill the system was a low-silicate heavy-duty coolant
pre-charged with Pencool 2000® supplemental coolant additive (SCA). The coolant served well for several years, and GM requires this type of coolant, fortified with an SCA in that family and age of trucks. In addition, SCA is required on an annual basis to replenish and extend the protective properties of the engine coolant. Ford has a similar requirement for Ford trucks with Navistar diesel engines. The SCA selected by Ford is the Fleetguard DCA-4® type chemistry. Today, antifreezes formulated with the SCAs may be purchased. Examples of this type of “Fully Formulated” coolant include OEM brands from Caterpillar, Detroit Diesel (PowerCool®), Cummins (Fleetguard Compleat®), Navistar (FleetCool®) and Mack. Aftermarket brands include Alliance, FleetCharge®, Quaker State Antifreeze. Heavy-Duty coolant should (and all those above do) meet ASTM D-6210 (and/or TMC RP-329). These coolants may be used in virtually any vehicle. Almost every truck and coach manufacturer in North America uses them as factory-fill.
• Make sure you are using acceptable quality water.
Yes, this requires a lab test. Most cities’ water is acceptable, but purified water is better. Well water is not usually acceptable. Hard water scale and other chemicals used to make good drinking water don’t always contribute to good coolant make-up water. Many suppliers now offer packaged coolants blended from 50% antifreeze and 50% deionized (DI) water. These are the best coolants to use.
• Use a 50/50 Mixing Ratio.
You almost always need a 50/50 mix. The antifreeze was formulated with this ratio as the standard when the calculations were made for inhibitor concentrations. There is no justification for using less than 50% antifreeze in most highway vehicles. In extremely cold climates, 60% antifreeze is used to provide freeze protection below -60°F. Operating at less than 50% antifreeze requires the assistance of professional coolant blenders and sophisticated SCA formulas. A few high-end coolant recyclers offer these services.
• Maintain Heavy-Duty Coolant.
All coolants should be checked every 3 months for correct freeze point. A refractometer is the best method, but test strips are pretty reliable too. According to a study by the ASTM, the majority of hydrometers (floating balls) are inaccurate. Consequently, hydrometer testing was removed from the approved methods list a few years ago. In addition, the SCA concentration in truck coolants must be maintained. Test strips are now dependable (use the right strip!) and are the easiest way to check. Use a quality, brand name SCA such as Pencool 3000® or Fleetguard DCA-4®. These products are available in liquid or filter forms, and are not expensive. Both of these meet the ASTM SCA specification. Check with the engine manufacturer for more information.
• Flush & Fill at 24 Months/30,000 miles.
Many OEMs are allowing extended service beyond these limits. They also allow oil changes at 7,500 miles in many cases. If you’re not comfortable letting your oil go 7,500 miles, you probably shouldn’t be comfortable ignoring your coolant for four or five years. It’s inexpensive insurance, and quality coolant recycling is becoming more available all the time, so there isn’t an environmental issue.
The Bottom Line
(Closing thoughts by I.M.)
Our specific radiator had essentially four major strikes against it right from the start:
1. The cooling system, with only 26% glycol, was loaded half short on coolant, and, the corresponding amount of inhibitors.
2. Being short on coolant meant it was high on water. And again, Waco Water turns out to be not “good” water for a cooling system.
3. & 4. This aluminum radiator is exceptionally large for being a light duty application. What it really needed was an extra batch of inhibitors with the initial coolant charge. What it unfortunately got was a short one—it probably came in at about 62 ppm silicates. Then, as soon as that coolant hit all those brand new, uncoated aluminum tubes, the plating action quickly consumed the available protectors. By the time the concentration of silicates degraded its final value of 9 ppm, there was not enough left to continue protecting the most vulnerable part of the radiator: The tube welds.
GM’s Preliminary Service Bulletin # 466201, April 1994, says in part: “All Medium Duty trucks built in Janesville, starting with the 1994 model year, have the Nalcool 2000 (now Pencool 2000) brand engine coolant additive standard. Nalcool 2000 has been standard with the CAT 3116 diesel engines since the start of the 1993 production, and optional with gas engines before 1994. Nalcool 2000 contains nitrites, which inhibit corrosion, the number one enemy of the cooling system. Correct use of Nalcool 2000 will reduce pitting corrosion of aluminum radiators and heater cores. Because the nitrite inhibitors wear out over time, Nalcool 2000 should be added to the truck cooling systems on an ongoing basis as an economical method of maintaining proper inhibitor levels. Specifically, Nalcool 2000 performs the following functions:
• Protects all six engine metals from corrosion
• Maintains the alkalinity (pH and RA) of the coolant
• Replenishes antifoam protection
• Controls scale formation to maintain cooling efficiency …”
Thought: Medium Duty or not, this 6.5 Liter diesel application appears to be as good a candidate for an SCA.
The bottom line of this scenario, though causing a fairly dramatic component failure in the process, turns out to be something less than earthshaking. The diagnosis is pretty much what we all guessed from the start. (Well, some of us might have thought it was an electrolysis problem at first.) The moral of the story is: don’t chintz on the coolant!
Thanks to Lynn Hassell, Renschler Auto Inc., and Ed Eaton of Amalgamated Laboratories for their assistance in producing this article. Now, as a direct comparison, wouldn’t it be nice to document a “real” electrolysis problem. (Any takers?)
In addition, maybe we could ask Ed to work on a piece for the next issue that would elaborate on the use of SCA’s, nitrites and the test kits that are available. This sounds like something that cooling system technicians should be well prepared for in the year 2000 and beyond.
For those interested, the cost for a comprehensive test and analysis like this starts at about $500. Sounds a little steep until you consider that the list price for one these 34” PTRs is $300+. It doesn’t take many unexplained failures of radiators like these to amortize the cost of such a test. This is especially so for whoever is picking up the cost of the replacements. To contact Amalgamated Laboratories, call 480-991-2901; Fax: 480-991-2903.