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Engine bay cleaning – basic

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The engine bay is an important part of the car, and many detailers want it looking like it is brand new, or even better: custom build. This means cleaning off a lot of dirt, grime and oils that are hard to remove. This basic guide will give you some pointers before you start.


What you can encounter

  • Caked on engine oil with carbon deposits in it, that have been reheated and cooled down many times.
  • Dust, dirt and sand that enters via gaps in the front.
  • Brake and/or transmission oil (that might have been spilled).
  • Dirty rainwater coming in from the front window.
  • Dried up wash-water from your weekly wash.
  • Tree-sap, leaves, insects and tar, all coming in from outside.
  • Iron fallout.
  • Heavily oxidized metal (like the exhaust, which gets really hot and then cools down again)

Cleaning products that might be of use to you

You’ll encounter a lot of dirt under the hood, but luckily the detailing-scene has a big arsenal of products that can help you out. Not everything can be done this way, but it will make a positive difference.

How to clean/prepare your engine bay with snowfoam

The use of snowfoam to clean your engine has become more popular the last few years. Mostly because there are more snowfoam products on the market, and they are also performing better then before. A snowfoam has great cleaning power on a car, and also has some effect on the dirt on the engine. The advantage is that snowfoam loosens up the dirt, making it much more easy to remove. The biggest downside is that snowfoam is just water and soap. And you need even more water to rinse it off. The engine bay was not designed to be hosed with water, nor are the electric components. So care needs to be taken to snowfoam an engine without any risk.

  • Check if the engine is completely cooled down
  • Check if all the lids are screwed on correctly
  • Check to see if you can find uncovered electric wires/connections
  • Put a plastic bag with some tape over electric components such as you CPU, fusebox, sparkplugs and the rotorhouse
  • Spray the snowfoam from a distance. You don’t want to spray it on under pressure. Try to lift the lance and spray from the top towards the ground. Try to stay away from areas with sensitive electrics
  • Leave the snowfoam to dwell, but not as long as you would with the paintwork (about half the time)
  • Spray off the water with the pressure washer, but keep the lance at a distance. You want to blow a mist of water over the engine, you don’t want to spray water under pressure from to close. It should be just enough to spray off the snowfoam
  • After the snowfoam has been rinsed off, dry the engine bay with a clean MF towel. Any water left behind can create waterspots when left to dry
  • If needed/wanted, you can continue straight away with some APC or another product to clean the very dirty spots that the snowfoam didn’t loosen up enough (see the steps below)

How to clean your engine bay by hand

Cleaning the engine by hand is probably the most safe way, and will give you the best (thorough) results. However, it is a very slow process that requires a lot of patience and great deal of trying to get in those small, little corners. However, once it has been done correctly, the results can be very impressive.

  • Check if there are any uncovered electrical wires/connections
  • Put a plastic bag over very sensitive electronics such as the CPU, alarms systems and your fusebox
  • With older engine, the rotorhousing is one of the parts that can fail when it gets wet, this can easily be avoided by putting a plastic bag over it
  • Start out in one corner and begin with a soft hair brush and some APC. Try to remove as much as you can
  • If you encounter very dirty/oily buildup that is difficult to remove, you can grab the Engine bay cleaner for some rough cleaning action (because this product is more expensive and not always very friendly on certain materials it is recommended to only use it when you need it. Don’t just spray it everywhere)
  • If you encounter very oily, tar or glue residue, you can use the Tar and Glue remover. Just remember to wipe it off thoroughly and if possible clean it afterwards with some APC
  • If you encounter any fallout, a iron fallout remover might help, just remember that many parts of the engine are made out of metals and several can react without the need to remove any fallout
  • You can possibly speed up the process if you spray an area with Traffic Film Remover before hitting it with the APC
  • The brake cleaner can be used for area’s close to the wheels, if you find some caked on dirt that even the Engine bay cleaner won’t shift
  • Agitating a cleaning product with a brush often works pretty good to improve its cleaning power
  • When you are done cleaning an area, take a spray-bottle with just water, spray it over the area and wipe the area clean. You might want to repeat this step because the APC can leave residue
  • When you are completely done with cleaning everything, you can use a dressing or plastic sealant to make the plastic look black again
  • The paintwork can be polished with a finishing polish, due to the little corners it might be best to polish it by hand
  • The metal parts can be polished with grade 0 steelwool and/or metal polish. A polishing ball/cone can speed up the process
  • The rubber pipes can be cleaned with a silicon remover before you put the dressing on
  • If you really want to use a protective product, you are better off using a ceramic coating or a sealant. Wax won’t survive the heat

General tips

Take care when you are cleaning the engine. There are several sensitive parts around the engine. Getting moisture in certain areas might cause engine problems. These are just some general tips to help you prevent the worst mistakes, but try to think before you act. You don’t want to have any engine problems after cleaning the engine bay.

  • Keep in mind that you shouldn’t remove the seals to much. Because you might remove some oily lubricants that are needed for proper functioning
  • Remember that the engine will get very hot when you apply any products in any area. Putting wax on the exhaust manifold will not work
  • Think about what you are cleaning. Some parts of the engine are very sensitive and don’t like moisture
  • If an area is very sensitive to moisture, you could just spray APC on a MF towel and wipe the area
  • Think before you use a heavy cleaner. It might remove the dirt, but it could damage the surface underneath the dirt
  • Take care around plugs and connectors, if moisture gets inside, it might cause an electrical problem
  • It is recommended to leave the engine for a few hours before you start it, just to increase the chance that any moisture is gone by the time you start the engine
  • Only work on a completely cooled down engine!
  • Polishing the exhaust manifold will not do much for long, the manifold gets really hot and will corrode eventually anyway
  • You might wanna where gloves. Not just before you’ll scrape your knuckles on many small, sharp parts, but also because the cleaning products will dry out your skin
  • Never, ever work on a engine when it’s running!
  • Resist the temptation to hose down the engine after cleaning, the water will run down and might run over plugs or connection that you didn’t notice
  • If you have an engine cover, don’t forget to take it off and clean underneath
  • Don’t take apart more then you are experienced with. Take for example the sprakplug leads, if these are put back in the wrong order, the engine won’t start
  • A steam cleaner might be a good help for small crevices and other hard to reach areas
  • You can use foam or cotton swabs to get into really small places

Cleaning the engine is a combination of dirty, rough work, but also something you need to take care with. Try to use as little liquid as possible, and wipe off an area as good as you can. The use of a dressing and/or a sealant can make the engine look fresh and new again.

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