Here's How Electrolysis Can Destroy Your Car's Cooling System

Your car's cooling system has one job — to keep the engine from cooking itself. But even with fresh coolant and a shiny new radiator, there's a silent killer that could be eating it from the inside out. You won't see it coming until it's too late. It's called electrolysis, and it's not to be confused with the hair-zapping kind. This electrolysis attacks your cooling system, not your follicles.

Electrolysis in the radiator happens when stray electrical current flows through your coolant, turning the liquid into a low-grade battery. That electricity looks for metal to ground itself, and in your engine bay, that means your radiator, heater core, and associated metal components of the cooling system. Over time, it corrodes from the inside, leading to pinhole leaks, cooling inefficiency, overheating, and eventual cooling system failures. 

Electrolysis may be a useful way to remove rust from parts, but it sure isn't good if it's happening inside your car's radiator. Modern vehicles are especially vulnerable thanks to the use of lightweight metals, ungrounded plastic radiator tanks, and all the electronic systems packed under the hood.

The first step to diagnose is to get a digital voltmeter. With the engine off, dip the positive lead into the coolant (don't let it touch the metal), and connect the negative to the battery's negative post. If you see more than three-tenths of a volt on the screen, congrats, your cooling system is part of an electrical circuit it was never designed for.

The damage doesn't show up like a blown fuse. It's slow and corrosive. Radiators develop internal leaks, residues form on core internals, and you'll find degraded radiator tubes and hoses. By the time you notice the temp gauge creeping up, the damage is already done.

Faulty grounds, poorly installed electric components and, basically, all electrical components that need grounding can introduce stray voltage. Combine that with aging or contaminated coolant creating a chemical imbalance, and you've got a perfect storm. Old coolant loses its additive package, becoming more conductive over time. So change the coolant, and change it often. Every two to five years is the rule of thumb, but check your owner's manual for recommendations.

Want to stop electrolysis before it melts your wallet? Fire up the engine, kill all electrical accessories, and slap that voltmeter on. Take a baseline reading, then rev it up to 2,000 rpm and check again. If the numbers spike on any component or accessory, you've probably found the troublemaker that's begging for a proper grounding. Make sure your battery terminals are clean, and corrosion-free. 

Use original-equipment-quality coolant. Mixing brands or topping off with hard water or tap water dilutes the corrosion inhibitors and increases the risk of component failure due to corrosion. Distilled water is what to go for, especially if you're using coolant concentrate or diluting your own 50/50 mix of antifreeze. If you've already got signs of electrolysis like black lines and holes on the radiator, mystery coolant loss due to leaks, or residue, get your system flushed and grounded correctly. And pressure-test everything.

Neglect it, and you're looking at a new radiator, failed heater cores, and even water pump or cylinder head damage. It's a slow bleed that ends in a big bill. Your car won't explode, but it could just slowly rot to death from the inside. That's worse, honestly.