Technology changed our cars and not just the old ones either. In fact, the effect technology had on them has probably been the most profound: disc brakes, air conditioning, overdrive transmissions, and fuel injection have made them feel near as new as the latest thing to roll off a showroom floor.
More recently the market has embraced another technological watershed: aluminum radiators—they're light, they're strong, and they're inexpensive. And while aluminum isn't as thermally efficient as copper, a properly built aluminum radiator actually performs within a few negligible percentage points of its copper-brass counterpart. Aluminum even requires the same care and products as their copper-brass counterparts.
But that doesn't make them alike. Aluminum won't forgive neglect … period. The mild neglect that wouldn't faze a copper-brass radiator can wipe out an aluminum one within a week. And for a follow-up punch aluminum radiators aren't as repairable as their traditional alternatives. So pay attention.
Dissimilar metals will react with each other if immersed in a solution called electrolyte. In that case the more noble metal will corrode the less noble (base) metal by robbing electrons from it. This passive reaction is called galvanic corrosion and it's the foundation for alkaline batteries.
This isn't a big problem with copper-brass radiators on iron engines because copper and brass are more noble than iron. When electrolytes form in those cooling systems the copper and brass attack the less noble iron. Because the iron is so thick it rarely, if ever, corrodes completely—the coolant usually just turns brown from rust. At worst the corrosion attacks the zinc elements in the radiator joints' solder and cause it to "bloom" or disintegrate, expand, and leak.
Things changed with the introduction of aluminum engine components. Because aluminum is far less noble than copper, brass, and iron it will corrode madly and sometimes completely in the presence of electrolyte. The thin components in aluminum radiators raise the stakes: a nearly imperceptible 1/32-inch-deep pit can poke a hole right through a tube wall.
It should be obvious by now that to protect aluminum radiators we need to prevent the formation of electrolytes. We'll tell you anyway but it's actually no different than what it takes to prevent electrolytes from forming in a cooling system with a copper-brass radiator. But we're going to go a little further and explain a few additional measures. Though we'll reveal them in the context of aluminum these practices are just as relevant to more traditional cooling systems.
To learn the ropes we consulted two experts who have complementary knowledge: Jay Miller and Leon Weidmann. Miller fields technical calls at AFCO Racing, one of the industry's preeminent aluminum-radiator manufacturers. Weidmann owns 112th Street Radiator in Tacoma, Washington, a shop his dad founded in the '60s, one of the few remaining shops that still repairs and re-cores radiators. The guy's seen and probably done it all. Both know what it takes to make a radiator survive.
See the electrolysis damage in this photo? Neither can we but it's there, buried deeply within the core, making an otherwise good radiator impossible to fix for less than a new radiator's cost. It underscores the importance of maintenance.
If designing a radiator mount take a tip from the OEM world and insulate it from the rest of the car with rubber mounts. If the radiator can't complete the electrical circuit to the chassis then the engine can't seek ground through it and wipe it out. Soft mounts also reduce fatigue, a real consideration with aluminum.
Straight water may be the most efficient cooling medium but it's not the best, especially in the presence of aluminum. "Running straight water is one of the biggest mistakes we see people make," Miller says.
Water in an engine is never pure. It picks up minerals from the castings that transform it into an effective electrolyte. The solution is simple: blend the water with antifreeze.
More than alter the coolant's freezing and boiling points, antifreeze prevents coolant from forming electrolytes. The traditional green coolant achieves its corrosion protection with additives like silicates and phosphates. The industry refers to them as Inorganic Additive Technology (IAT).
Though effective for all metals, these silicates and phosphates precipitate from the solution within about two years. That leaves the system vulnerable to electrolyte formation. Worse yet, those deposits hold electrolytes against the radiator walls like a sponge. Weidmann doesn't recommend it but he maintains that the old-style antifreezes will actually work just fine if maintained religiously. "You just have to change it like clockwork," he notes. "Every two years. Any longer and you're asking for trouble."
Probably because they know people largely neglect their cars and that more vulnerable aluminum components were on the horizon, antifreeze manufacturers developed formulas that use Organic Acid Technology (OAT) to prevent electrolyte formation. These extended-life antifreezes last a lot longer: five years or 150,000 miles. In fact that's what Weidmann and Miller recommend.
But all extended-life antifreezes aren't created equal; some formulas like DEX-COOL use a compound that reportedly attacks silicone and some nylons. Furthermore, DEX-COOL isn't compatible with traditional IAT antifreezes and mixing them can turn coolant to pudding.
"But the other extended-life coolants are great," Weidmann says, and uses them exclusively. "They offer the most protection and they won't fill up (the radiator's) tank with mud," he maintains. As far as recommendations, "I would use whatever the engine manufacturer recommends for the engine," Miller says. "We just recommend a good-quality antifreeze with water." A coolant such as AMSOIL INC. antifreeze is an ideal choice and a mix ratio of 50/50 antifreeze to water is ideal.
Though the manufacturers claim extended-life coolants are good for five years and 150,000 miles, both Miller and Weidmann recommend changing them at shorter intervals. Specifically Weidmann recommends every three years. "When coolant goes bad it turns destructive," Miller adds. "Antifreeze is cheap so why take the chance?"
Consider low-mineral or distilled water mixed with long-life antifreeze an aluminum radiator's primary defense from destructive galvanic corrosion and electrolysis. If possible, choose an antifreeze that advertises compatibility with all types.
Some deem additives redundant in a properly mixed coolant formula but others consider them an extra measure of performance. AMSOIL INC. bills its Dominator Coolant Boost partly by its ability to reduce corrosion when refreshed annually.