Professional Engine Bay Detailing and Protection Guide (Jan 2026)

Ensure the engine is cool to the touch. In an Australian summer, this may require the car to sit in a shaded garage for 3-4 hours. Applying cold water or chemicals to a hot engine block can cause thermal shock, leading to cracked manifolds or warped components. The surface should be no warmer than 30°C.

Identify sensitive areas including the alternator, fuse box, air intake (especially if an open-pod filter is installed), and any exposed ECU wiring. Wrap these tightly in aluminium foil or plastic cling film. Foil is preferred as it holds its shape better around irregular brackets and stays in place during rinsing.

Before introducing liquids, use a vacuum or compressed air to blow out loose leaves, gum tree nuts, and heavy red dust deposits from the scuttle panel (base of the windscreen) and corners of the engine bay. This prevents the formation of 'mud' which can clog drainage channels.

Mix your degreaser in a dedicated spray bottle. For a standard engine, a 1:10 ratio of a high-quality concentrate is sufficient. For 4x4s with heavy oil blow-by or red dust staining, increase the strength to 1:5. Always use distilled water for mixing if your local tap water is 'hard' to prevent spotting.

Gently mist the entire engine bay with water to loosen surface dust. Do not use high pressure at this stage; the goal is simply to hydrate the dirt so the chemicals can penetrate more effectively. Avoid direct spray on the covered electrical components.

Apply your diluted degreaser liberally, starting from the lowest points and working upward. Ensure you coat the underside of the bonnet (hood) if it does not have a fabric liner. Focus on the firewall and the lower engine block where oil residue accumulates.

Allow the chemical to dwell for 3 to 5 minutes. In high-temperature conditions, ensure the product does not dry on the surface. If it begins to dry, mist it lightly with more degreaser or water to keep it active. You will see the grime starting to liquefy and turn brown.

Using your boar's hair brush, work the degreaser into the nooks and crannies. Pay special attention to bolt heads, battery terminals (if sealed), and plastic covers. Agitation is key to breaking the static bond of Australian red dust which is notoriously 'sticky' due to its iron oxide content.

Scrub the painted metal underside of the bonnet with a soft microfibre mitt and APC. If a fabric heat liner is present, do not soak it; instead, lightly mist with APC and wipe with a damp cloth to avoid sagging or adhesive failure.

Switch to a smaller, soft-tipped brush for intricate areas like fuel injectors, vacuum lines, and the spaces between the intake manifold runners. This level of detail is what separates a professional clean from a quick 'wash-down'.

Rinse the engine bay using a wide fan spray. Keep the nozzle moving constantly and do not linger on any single electrical connector. Rinse until the water runs clear and no white foam remains in the crevices. Ensure all degreaser is flushed from the chassis rails.

Carefully remove the foil or plastic wrap from the alternator and intake. Inspect the areas for any missed spots. If grease remains, perform a spot-clean with a microfibre towel soaked in degreaser rather than re-wetting the entire engine.

This is the most critical step. Use a leaf blower or dedicated car dryer to blast water out of all recesses. Direct air into spark plug wells, fuse box seams, and multi-pin connectors. Standing water in these areas can cause immediate sensor errors or long-term corrosion.

Use clean microfibre towels to wipe down the flat surfaces, hoses, and the inner guards. This prevents water spotting, which is particularly visible on black plastic components in high-UV environments.

Apply a water-based dressing like Aerospace 303 to all plastic and rubber surfaces. Spray it onto an applicator pad first, then wipe onto the surfaces. This provides UV protection and prevents the 'chalky' white appearance common in older vehicles. It also makes future dust removal much easier.

After 10 minutes of dwell time for the dressing, use a dry microfibre towel to buff off any excess. This leaves a factory-satin finish rather than a greasy shine, ensuring that dust will not stick to the surfaces during your next drive.

Start the engine and let it idle for 5-10 minutes. The heat generated by the engine will help evaporate any remaining microscopic moisture in hard-to-reach areas. Watch the dashboard for any warning lights during this period.