The short answer: rinse the body and underbody as soon as you're off the sand, wash with a strong 4WD wash, flush the chassis rails to get trapped salt and sand out, then dry and protect exposed metal. The chassis flush is the step most people skip, and it's the one that matters most for rust.
Why beach driving is so hard on a 4WD
Salt spray and wet sand pack into chassis rails, suspension mounts, wheel arches and the back of the bumper. A hose on the outside doesn't reach inside the rails, so salt sits there, holding moisture, and rust starts from the inside out.
What you'll need
- 4WD & RV Wash: a stronger alkaline wash for mud, salt, bugs and road grime.
- Chassis Flush Solution: formulated to remove salt, mud, sand and clay from underbody components.
- The Captain's Musket foam gun, with the Chassis Grenade nozzle for flushing inside the rails.
- Grease Attack citrus degreaser for diffs, suspension and the engine bay.
- A hard bristle brush for arches and mud flaps.
- Chassis Champ or lanolin spray to protect the underbody once it's dry.
Or start with a 4WD cleaning kit. Kits start at $99.
Step 1: Rinse the underbody first
Before anything else, rinse under the vehicle: wheel arches, the inside of the bumpers, suspension and the chassis rails. Get the bulk of the sand off before it dries.
Step 2: Foam the body
Cover the 4WD in 4WD & RV Wash foam and let it dwell for a few minutes, out of direct sun. It loosens salt film, mud and bugs so you're not dragging grit across the paint.
Step 3: Degrease the dirty bits
Hit diffs, suspension and the engine bay with Grease Attack, then agitate with the hard bristle brush. Avoid spraying directly into exposed electrical components or air intakes.
Step 4: Flush the chassis rails
This is the important one. Use Chassis Flush through the Captain's Musket with the Chassis Grenade nozzle. Its 360° rotating spray flushes salt and sand out of the inside of the rails better than a straight nozzle. Work from the front of each rail to the back until the water runs clear. More detail: how to clean a 4WD underbody and chassis rails.
Step 5: Contact wash and rinse
Wash top to bottom with a Wooly Wash pillow, then rinse everything, including under the vehicle again.
Step 6: Dry and protect
Dry the body with a Big Mike towel. Once the underbody is dry, spray exposed metal, suspension components and wheel arches with Chassis Champ or lanolin spray. Finish the tyres with Tyre Shine.
How often?
After every beach trip, rinse, wash and flush the chassis the same day if you can. Re-apply underbody protection when the coating starts to wear, and after heavy washing.
FAQs
Is 4WD & RV Wash safe on paint?
Yes. It's safe on paint, glass, plastics, rubber, chrome and alloy wheels. For regular washes on a ceramic-coated 4WD, our pH-neutral Car Wash is gentler.
Do I need a pressure washer?
No. The Captain's Musket on a garden hose handles foaming and chassis flushing. A pressure washer is faster for heavy mud.
Will a chassis flush stop rust that's already started?
It removes the salt that causes it. Treat existing rust separately, then protect the area with Chassis Champ or lanolin.
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