Keeping Your Undercarriage From Rotting Away

Stop trying to spray upwards with a standard hose nozzle, you won't get the angles right and you'll just get soaked. Get yourself a proper underbody water broom or a curved pressure washer lance. I reckon the ones from Bowden's Own or even a cheapie off eBay make a world of difference. It lets you reach right over the diffs and into the nooks where salt hides. I learned this the hard way after a beach trip to Fraser; I thought I'd rinsed it well, but a week later I found a literal kilo of sand still sitting on top of the fuel tank.

Water alone doesn't always cut it if you've been driving through salt spray or on the sand. Salt is sticky stuff. I always use a salt neutralising wash (like Salt-Off or similar). You just click it into your hose line and it breaks down the salt crystals chemically. Truth be told, I won't even let my missus take her car near the coast without a fresh coat of protection underneath and a proper chemical rinse when she gets back.

If you're heading out into the red dust or doing beach runs, give the underside a light spray with a lanolin-based protectant like Lanotec or Inox. It's made from sheep juice (seriously) and it creates a barrier that stop stuff sticking. Some blokes swear by fish oil, but honestly, it stinks like a dead whale for a month. Lanolin is much better. Just don't go overboard near your brake rotors for obvious reasons.

Chassis rails are hollow. Most people wash the outside, but the mud and salt sit inside the rail and rot it from the inside out. Stick your hose or pressure wand into the drainage holes along the rail and flush them until the water runs clear. I once had a customer bring in a Hilux that looked mint, but when we flushed the rails, about five kilos of wet red mud came out. That mud stays wet for weeks, just eating the steel. Disgusting.