Many people firmly believe that engines and water do not mix. To a certain extent this is true. Anyone who has hit deep standing water and suffered a bent connecting rod as a result of water being drawn into the engine through the air intake will testify to this. However, as long as water isn't drawn into the engine, or allowed to saturate electrical contacts, it will not cause any problems. The proof of this can be seen on cars like the Lotus Elise, where the engine bay is effectively open to the atmosphere (and therefore rainfall) due to the number of cooling vents in the cover. So, what does this mean for engine bay detailing? Well, it means that you can hose off the engine bay without fear of causing any damage, providing that you cover the air intake and any sensitive electrical parts first.

Safe in the knowledge that you can safely hose your engine bay off, the next question you might ask is how will this help? Surely grease and grime cannot simply be hosed off? The answer is it can't; what you need to do first is break down the grease and grime using a degreaser. Up until fairly recently engine degreasers generally comprised potent mixtures of aggressive solvents, which were tremendously effective at cleaning but not very safe to work with and also not at all environmentally friendly. Fortunately, progress has been made to the extent that it is now possible to buy degreasers that comprise advanced detergent formulas and natural solvents, which makes them more environmentally friendly and safer to work with. The cleaning power of these products is almost as good as that of traditional degreasers provided they are agitated and given sufficient time to work.

Once the engine bay is clean and dry, all you finally need to do is dress and protect all of the surfaces. This is very straightforward, as you are dealing with materials that are found elsewhere on your car, namely plastics, rubber, metals, and painted surfaces. As such, you can use the same detailing products to great effect. Painted surfaces can easily and quickly be protected using a sealant or wax. Plastic engine covers and components can be restored to as new condition using a trim restorer or a surface dressing. Rubber hoses can be nourished and protected using a surface dressing or a tyre dressing. Most metal surfaces can be polished and protected using metal polishes and sealants, although this often requires more elbow grease (we frequently use a Dremel power tool in order to make lighter work of metal polishing duties).

Recommended: R222 Total Auto Wash

Recommended: Raceglaze Detailing Brush Set

Recommended: 303 Aerospace Protectant

When it actually comes to the cleaning process, the first thing you should do is make sure your engine is cool; never try and clean a hot engine. This is because products will dry too quickly and leave stains, and you could also burn yourself if you don't know your way around the engine bay. The next thing you should do is cover the air intake and any sensitive electrical parts. The best material for covering these components is aluminium foil. This may seem like a strange choice, but it actually makes a lot of sense, as it is very easy to mould over awkward shaped parts and it is 100 % waterproof providing that you don't tear it (it is also fully safe for modern engines as all electrical connections are housed in insulating plastics). Note that you do not have to fully seal every part you are covering; all you are doing is creating a mini umbrella that will prevent water ingress or pooling in or around sensitive components. To make the most of the umbrella effect you should only rinse off from a high angle.

Once the air intake and any sensitive electrical parts are safely covered, the next thing you should do is spray a degreaser over the entire engine bay, covering all surfaces, including the underside of the bonnet (although you may want to skip this latter step if you have a felt sound proofing cover secured in place, as they take ages to dry). Try to avoid spraying the front bumper and the wings; degreasers will strip existing sealant or wax protection. If you accidentally spray these areas, rinse them off with the hose and reapply sealant or wax protection at your earliest convenience. Once you have sprayed all of the surfaces, agitate thoroughly with soft brushes and then leave the degreaser to work for 10 - 15 minutes. On a hot day you should leave less time, as you should not allow the degreaser to dry on any parts as it may then cause staining.

A typically dirty and grimey engine bay in need of a good wash and spruce up

A gentle engine degreaser is applied, agitated and left to soak to loosen all of the grime

After 10 - 15 minutes the degreaser is rinsed off, taking all of the grime with it

After waiting 10 - 15 minutes, the next thing you should do is rinse off the entire engine bay, including the underside of the bonnet if necessary. Under no circumstances should you use high pressure water for rinsing off; you don't want to drive water into any components. A normal hose with the spray attachment set to a wide angle or a pressure washer turned down to the lowest setting is perfect, as both options provide enough force to carry away all of the loosened grease and grime without risking ingress. Rinse off thoroughly but for no longer than necessary; once the suds have disappeared the job is done. After quickly removing all of the foil coverings the next thing you should do is start your engine, in order to help to start the drying process. You should only leave it running for a couple of minutes though, as you don't want it to become too warm, as this will adversely affect the application of surface dressings afterwards. After switching off the engine, finish the drying process using microfibre towels.

After rinsing off all surfaces should be dried thoroughly using microfibre towels

All plastics and rubber surfaces should then be dressed with a trim protectant

Washed, dried and protected, and now looking like new again... in less than an hour!

With the engine bay now clean and dry the penultimate thing you should do is dress and protect all of the surfaces. Painted surfaces can easily and quickly be protected using a sealant or a wax. Plastic engine covers and components can be restored to as new condition using a trim restorer or a surface dressing, applied using either a foam pad or a microfibre pad. Rubber hoses can be nourished and protected using a surface dressing or a tyre dressing, again applied using either a foam pad or a microfibre pad. Most metal surfaces can be polished and protected using metal polishes and sealants, although this often requires more elbow grease (we frequently use a Dremel power tool in order to make lighter work of metal polishing duties).

The final step in the cleaning process is to pack away all of the tools you have used, making sure everything is clean and ready for next use. All towels and applicator pads should be washed in a washing machine at a low temperature using a non-biological liquid detergent (avoid soap powders and detergents containing bleach or fabric softeners) before being allowed to dry out naturally.