Don't Use Tap Water To Cool Your Engine. Here's Why

Once upon a time, this engine powered a sporty 1995 Nissan 240SX. It’s a KA24DE, the double overhead cam version of the 2.4-liter four-cylinder that powered a plethora of Nissans through the decades, from the 240 to the Frontier. This one served up thrills for 230,000 miles, and it could’ve gone further had it not been neglected.

That’s the conclusion reached in this recent teardown from the I Do Cars YouTube channel. It wasn’t an easy project—this video took several days and considerable effort to put together, according to the host, Eric. The engine came from a wrecked 240SX, though how the car was wrecked is a mystery. Evidence pointed to the engine being bad before the crash, not as a result of the collision. But that doesn’t matter. This engine is well and truly done for.

It’s no big mystery as to what happened. From the very beginning, there are signs of water intrusion into areas where water shouldn’t go. Icky orange goo and mineral deposits are found on the spark plugs. Digging down to remove the intake, more rusty crud and deposits come through on coolant hoses. And when the head comes off, everything becomes painfully obvious. This engine had ordinary tap water running through its cooling system, and not as a temporary measure to get a wounded car back home.

As a result, minerals found in the water eventually caused reactions with the iron and aluminum in the engine, leading to the orange rusty sludge found throughout the internals. The sludge eventually plugged up cooling passages, which led to overheating issues and ultimately, a failed head gasket. The water you see lying in the cylinders? That wasn’t a result of the engine sitting outside unprotected from the elements. Milky sludge in the oil pan further confirms this KA had a head gasket failure, causing water and oil to mix.

If proper coolant had been used, this probably wouldn’t have happened. Furthermore, if the engine had been repaired after the gasket failure, it may have been salvageable. Instead, even the cam lobes were rusty from all the moisture in the mill. The crankshaft is rusty, the head is rusty, and the pistons were literally beaten with a hammer to get them free of the block.

Pouring water in the radiator can certainly work in a pinch to keep your engine cool, but be sure not to keep it there for long. There’s a reason engine coolant exists, and it’s not just to keep things from freezing or boiling.