Electrolysis is one of the most destructive causes of premature truck radiator failure. Stray electrical current passing through the engine coolant attacks the metal components from the inside out, often causing damage that is mistaken for a manufacturing defect. Here are four key ways electrolysis can damage a heavy-duty truck radiator:

Pinhole Leaks in the Tubes

• Electrolysis removes microscopic amounts of metal from the radiator tubes, creating tiny pinholes. These leaks may begin as a slow coolant loss but can quickly worsen, leading to overheating, coolant contamination, and costly downtime.

Internal Corrosion and Metal Erosion

• Stray electrical current accelerates corrosion inside the radiator core. As aluminum, copper, or brass surfaces deteriorate, the tube walls become thinner and weaker, significantly reducing the radiator's service life and increasing the risk of catastrophic failure.

Reduced Cooling Efficiency

• Electrolysis can produce corrosion deposits and oxide buildup inside the coolant passages. These deposits restrict coolant flow and reduce heat transfer, making the radiator less efficient at dissipating engine heat. The result is higher operating temperatures and an increased likelihood of engine overheating.

Premature Core Failure

• Continuous electrolysis weakens critical components such as tubes, headers, and brazed or soldered joints. Over time, the structural integrity of the radiator core is compromised, often requiring complete radiator replacement instead of a simple repair.

Preventing Electrolysis Damage In A Heavy Duty Truck Radiator

To help prevent electrolysis-related radiator failures:

• Regularly test for stray electrical voltage in the cooling system (anything above approximately 0.3 volts DC should be investigated).
• Maintain proper engine and chassis grounding.
• Use the manufacturer-recommended coolant and maintain the correct coolant chemistry.
• Replace coolant at the recommended service intervals and ensure the cooling system is properly maintained.

Early detection and correction of electrolysis can significantly extend radiator life, reduce repair costs, and help keep heavy-duty trucks operating reliably.

How To Test For Electrolysis In A Heavy Duty Truck Radiator

Warm the Engine

• Fill the cooling system to the proper level.
• Start the engine and allow it to reach normal operating temperature.
• Ensure the coolant is circulating.

Set Up a Digital Multimeter

• Use a digital multimeter (DMM).
• Set the meter to measure DC volts on the lowest voltage scale (typically 12V DC).

Connect the Multimeter

• Connect the negative (black) lead to a clean engine ground or directly to the negative battery terminal.
• Remove the radiator cap or surge tank cap (only when it is safe and the system is not under pressure).
• Carefully place the positive (red) lead into the coolant, ensuring it touches only the coolant and does not touch the radiator neck, filler tube, or any metal component.

Read the Voltage

Interpret the reading as follows:

If the voltage exceeds the recommended limit:

• Inspect all battery cables and ground straps.
• Check engine-to-frame and cab-to-frame ground connections.
• Check the starter ground for corrosion and connection.
• Check the radiator ground strap (if equipped) connection.
• Clean corroded or loose ground terminals.
• Verify alternator output and check for AC ripple, which can indicate a failing diode.
• Inspect aftermarket electrical accessories (lights, radios, inverters, heaters, PTO equipment, etc.) for improper grounding.
• Retest the cooling system after each repair to confirm the voltage has returned to an acceptable level.

Best Practices:

• Contaminated (acidic) coolant will negatively affect the reading and it could be the cause of the electrolysis.
• Always complete an electrolysis test using new coolant as per the OE vehicle manufacturer’s specifications.
• Perform the test with electrical accessories turned off, then repeat with headlights, HVAC blowers, PTOs, or other accessories on. A change in voltage can help identify the source of stray current.
• Include an electrolysis test whenever replacing a radiator or performing major cooling system repairs. This helps prevent a new radiator from failing due to an unresolved electrical issue.
• Always flush the cooling system before replacing the coolant.
• Always replace the coolant with pre-mixed coolant or properly mix the coolant with distilled water as per the OE vehicle manufacturer’s specifications.
• Always flush the cooling system and replace the coolant when replacing the radiator.

A five-minute electrolysis test can prevent premature radiator failure, coolant leaks, and costly engine overheating by identifying electrical problems before they damage the cooling system.

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