What Is Electrolysis?
Electrolysis is an electrochemical corrosion process that occurs when stray electrical current flows through the cooling system. When the engine or vehicle chassis is not properly grounded, electrical current seeks an alternative path to ground, often through the coolant and radiator. This stray current causes rapid deterioration of aluminum components, creating pinhole leaks that destroy radiators from the inside out.
The damage is often invisible until it's too late. Tiny pinholes develop in the radiator tubes, tanks, and headers. The coolant may become discolored or develop a metallic taste. By the time you notice coolant loss, significant damage has already occurred. Electrolysis is the number one cause of premature aluminum radiator failure and is not covered under warranty.
Common causes include faulty ground straps, aftermarket accessories wired without proper grounds, corroded battery cables, and electric fan motors grounded through the radiator mounting points instead of directly to the chassis.
How Can I Test For It?
Testing for electrolysis is simple and requires only a standard volt/ohm meter (multimeter). Perform this test with the engine running and warmed up to operating temperature. Follow these steps carefully:
- Set your volt/ohm meter to the DC volts scale, 20-volt range or auto-range.
- Start the engine and allow it to reach normal operating temperature with the radiator cap removed (or overflow tank cap).
- Place the negative (black) probe on a good, clean engine ground, directly on the engine block or negative battery terminal.
- Submerge the positive (red) probe into the coolant in the radiator filler neck. Do not touch the probe to any metal surfaces, only the coolant itself.
- Read the voltage. A reading above 0.10 volts (100 millivolts) indicates an electrolysis problem that must be corrected immediately.
- To isolate the source, turn on/off individual circuits one at a time (lights, fan, A/C, accessories) while watching the meter. When the voltage spikes, you've found the offending circuit.
- Ensure proper engine-to-chassis grounding. Use heavy-gauge ground straps from the engine block to the vehicle frame. Inspect and clean all ground connections regularly. Corrosion is the enemy.
- Ground all electrical accessories directly to the chassis or battery. Never ground electric fans, lights, or aftermarket accessories through the radiator, heater core, or any cooling system component.
- Install a dedicated ground strap from the radiator to the chassis. This provides a low-resistance path that prevents stray current from traveling through the coolant. Use a minimum 8-gauge braided ground strap.
- Inspect and maintain battery cables and connections. Corroded, loose, or undersized battery cables force electrical current to find alternative ground paths through the cooling system. Replace cables showing any signs of corrosion or damage.