Clean Your Underside

Clean Your Underside

It’s a common problem but how many people clean the underside of their vehicle, and more importantly how many people do it correctly.

Imagine the scenario, you go out for a weekend for a spot of off roading and hit some rough trails, or it rained and you get swamped in mud, or the stream you regularly cross had risen to very high levels and was full of dirty water which was full of mud and leaves as well as bits of twigs and even grass, so here is the problem. This water, mud, and even dust has to go somewhere and when it goes under your vehicle it enters chassis sections as they are full of holes, it enters crossmembers as often they are fairly open, it enters outriggers and blocks the drain holes, and it even gets between close fitting components such as fuel tanks and their guards and even into brake components.

What do most people do? In most cases they get out the jetwash and hit the underside of the vehicle and this is the first mistake, you never use a jetwash on the underside of a vehicle as the pressures involved can easily force water past CV gaiters and steering rack gaiters and mix with any oils of fluids and damage the component and its moving parts or seals.
Always use a hosepipe as these are low pressure items and the vehicle components such as gaiters are designed to withstand these low pressure hosepipes and by using a hosepipe you automatically prevent future problems, and if your vehicle is so caked in mud you are often better carefully scraping off what you can first.

Begin by parking your vehicle on a slope if possible, and with the front end at the highest point and then get it even higher using axle stands or ramps to give you room to get underneath, and this is for good reason, when you get your hose on the underside you will get water dripping off and this runs away from you, downhill so you aren’t lying in it and getting wet.
Begin at the rear of the vehicle and wet everything through by using a coarse mist by adjusting your hose to this setting, and remember that wet mud is easier to remove then dry mud, and never forget to get on top of fuel tanks, chassis and under any protection plates or plastics and inside your chassis rails and crossmembers and any outriggers you may have. Leave this for a few minutes so any detritus collects the water and soaks it up to wet it through, thoroughly.

With everything wet through you can set your hose nozzle to a jet setting and work from the top down, this means blasting the top of your fuel tank so mud and dirt runs off it and downwards and you can usually hit the insides of any plastic bumper covers with the jet to remove any accumulated dirt from inside there. Always remember the top of the exhaust and rear suspension as well as any rear differential housings, particularly aluminium items as they use their exposed surfaces to cool themselves and any lubricants they contain and use as much water as you can until it runs clean and free of dirt and other particles. Make sure you get behind any protection plastics high on the vehicle and work your way downwards until you get to the bottom of the underside of the vehicle where you can get between items such as fuel tanks and their guards to prevent a build-up of dirt which can literally abrade the bottom of a steel fuel tank until it becomes so thin that it leaks.
Make sure you work from each side of the vehicle and clean out every outrigger until they are clean and poke out any drain holes so they don’t become clogged up with dirt being washed from inside them.

Next we use any holes in the chassis to clean this out, most chassis sections have multiple holes in them and we literally blast through these holes and with our vehicle pointing uphill any rubbish will come out through holes further down the chassis, or out of the end of the chassis if the ends are open, and clean the rear section a little at a time to ensure its insides are fully cleaned.

With the rear end of the vehicle cleaned we turn the vehicle around so the back end is in the air, either jacked up, or placed on axle stands, or with the rear wheels on ramps.
If you take extra time to clean the front end of your vehicle you can spray degreaser under your engine, gearbox, and transfer case as this will remove any oils or residues of oils when you clean off the mud, and this is beneficial for several reasons. If you have any oil or fluid leaks it will help in identifying them as a clean engine is much easier to see when looking for fluid leaks; engine sumps, gearboxes, transfer cases, and exhaust pipes all require their metal surfaces exposing to moving air to cool them which is reason enough to keep these surfaces clean.
Begin at the bottom of engines and gearbox assemblies and work upwards, with the underside clean you can clean out the chassis rails insides in the same way as you cleaned the rear of the vehicle.

Remember to do the insides of the front wheels to remove anything from inside the wheel rims and where the ABS reluctor rings are located as this will also clean the ABS sensors if they are externally mounted. Leaving these dirty can cause immense problems with the ABS system (if fitted) and cause the warning lights to come on and make you think of a massive expense when all that is needed is to keep the system clean. Cleaning the insides of the wheels will also help prevent any vibrations from an imbalance caused by mud sticking to the insides of the rims, and it will keep brake dust down.

Move under the bonnet and flush the upper part of the engine using degreaser of appropriate, and then from inside the engine bay you flush through the radiator fins to push any dirt out, the way it came in, and then do the underbody interior such as the inner wings. Flush through any top holes in the front chassis rails or horn extensions and crossmembers and remove all the mud and then flush through any transmission or gearbox coolers if you have them fitted.