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Preventing EME

Automotive engines have undergone serious changes in the past few years as they have become lighter and far more powerful. These changes can have significant impact on the cores rebuilders receive for rebuilding.

In search of lighter engine components, casting technology which was considered "thin wall casting" in the ’60s and ’70s has developed to the point where material thickness of all parts is controlled to a degree thought impossible in the past. New materials are being used in engines including carbon/resin composites, five times as much aluminum, and plain old plastic (not so plain and actually not so old).

All of this new lightweight casting and materials-substitution technology has allowed manufacturers to build lighter cars and meet CAFE mileage standards, which would have been impossible without them. That’s the "upside," with primarily all of the benefits going to the manufacturers. Sure, the cars are better examples of efficiency and engineering, but they are not without problems automobile owners never faced in the past.

Of all the potential high cost problems which are waiting for the new vehicle owner and the rebuilder, EME (electrolytic metal erosion) may be one of the most serious. Every engine rebuilder that has disassembled a bi-metal engine has found EME. New vehicles with computer controls and electrical sensors attached to the cooling system and engine suffer even more EME related problems.

It has actually been about 30 years since EME started to make its presence known in the automotive world. Now, the ever increasing use of aluminum engine components (plus a higher reliance upon electronics) has brought the problem to the forefront. But, it still remains hidden for the most part, because it is often mistaken for corrosion caused by oxidation in the cooling system. Or, it is mistaken for erosion caused by the flow of cooling fluid through and around the insides of an engine. Sometimes it is simply dismissed as being caused by a defective casting.

All of these causes can result in damage to engine parts which come in contact with the cooling fluid of a modern vehicle. However, they are not the major culprit.

In the marine industry, the use of zinc anodes has long been used in cast iron environments. It is "sacrificed" so the cast iron lives. Now, with bi-metal automotive engines a similar solution is available to solve the problem of EME. To stop this erosion, an anode made of a metal far more active, and higher on the atomic chart, needs to be introduced into the vehicle’s system so it will be eaten up rather than the aluminum or cast iron and steel engine parts.

Below you will find a table listing the major EME damage found on aluminum components in contact with the cooling systems on most of the engines used in the United States. These components include: front timing covers, thermostat housings, cylinder heads, intake manifolds and engine blocks.

Of the total number of problems presented, 43% are cylinder head related, many of which cannot be repaired. About 33% are related to the front engine timing cover and/or thermostat housing, and another 23% relate to damaged intake manifolds. This does not take into account the aluminum core radiators, heater cores or any of the other aluminum components independent of the engine itself.

Evidence of EME related problems has lead some engine coolant manufacturers to add protection to their coolants to try to prevent or lessen this damage. But, fighting the problem with chemical solutions is difficult and unproven to a great extent. And the expense to have coolant changed annually presents another obstacle to the vehicle owner.

Working with an engine rebuilder in Martinez, CA, an easy method for measuring the EME activity in any engine’s cooling system was discovered. What is this method? A simple multi-meter is the answer. All that is required is to open the cooling system at the radiator cap, stick the positive probe of the meter into the cooling system and ground the negative probe to the engine block. With the meter set at the lowest setting for voltage, you’ll find between 1/2 volt to 1-3/4 volts of electrical activity in the cooling system of just about every vehicle you test.

This electrical activity is not a voltage leak from the electronics in the vehicle; when the battery is disconnected the same voltage is still found in the cooling system. The problem is actually the cooling system acting like a storage battery. That would be a good thing if it could cool the engine without damaging components at the same time it stores electrical energy to operate the vehicle’s electronics and electrical system. But, that is not the case.

The actual readings obtained from a base sample of five different vehicles of different constructions, ages and types were quite surprising. These included a Ferrari sports car, 1.2 volts (all aluminum V8 engine with overhead cams and plenty of horsepower); a Buick sedan, 1.5 volts (V6 with aluminum intake and water pump); a Dodge Dakota pickup, 1.55 volts (V6 engine, plastic radiator tank, aluminum intake and a few other components in the cooling system); and finally a Chevrolet Suburban, 1.15 volts (aluminum aftermarket heads, cast iron block and sundry other cooling system components).

The solution which has been developed to fight this problem is a new product called the "Rad Cap," which uses proven marine sacrificial anode technology which has been adapted to the automotive market. This new radiator cap has a sacrificial anode made of magnesium which is mounted to the bottom of the cap below the seal, so the anode is always in the coolant stream.

The anode is manufactured from a more active metal composition than the aluminum inside the engine, therefore it gets eaten before the aluminum engine components. This really works, as proven by the same multi-meter test undertaken with this anode immersed in the radiator coolant. The electrical energy usually doubles at the anode, compared to the same coolant solution without the anode. This makes it clear that increased voltage at the anode will result in it being eaten before the engine parts which are at risk.

DD&E, developers of the Rad Cap, mounted the anode directly on the radiator cap so it would reach the liquid of the cooling system. The company says that EME damage will be diminished significantly in vehicles, regardless if they are driven regularly or simply parked and stored.

Once installed, the cooling system should be checked regularly and the radiator cap changed when it’s effective life span of about 18-36 months has been reached. Some vehicles will take a lot longer to eat away the anode. This can be the case even with identical vehicles with the same engine combination due to different electrical activity levels within the system.

Knowing that you are saving your customer potential damage to expensive internal engine components, and helping to ensure that core parts are in a better rebuildable condition may make use of the Rad Cap a worthwhile investment for your shop. The suggested retail price of the Rad Cap is $20. For further information on the device contact DD&E directly at 510-689-6214.