Method 1 (Using a pressure washer)
Assess the amount of grease and grime, as this will affect your decision about how you want to proceed with the cleaning.
You can pre-clean very carefully with a pressure washer, to help remove most of the loose grease, dirt and grime. Then use a degreaser with a brush, to clean away any stubborn, remaining dirt from the engine and surrounding area.
Method 2. (This uses water again, like Method 1, but no pressure washer)
Alternatively, we recommend a safer method. Do not pre-rinse the area with a pressure washer, instead, spray the degreaser directly onto the engine surface, leave for the requisite amount of time advised by the manufacturer, then agitate the area with a brush. Rinse the area you have cleaned carefully. This technique uses less water, there for, there is less chance of getting water in the wrong place. Which helps to prevent the chance of damage to the engine.
After removing any leaves or other debris, you need to wet the surfaces before spraying any chemicals on to them; this helps to reduce the possibility of the product drying while cleaning the engine bay.
If the engine is not too dirty, you can use an all purpose cleaner but for dirty, heavy grease, or oil covered engines, these will need treating with a degreaser to help dissolve the grease and oil residue first.
To clean all the surfaces of the engine, you will require many different sizes and types of brushes to enable you to reach the awkward and difficult areas of the engine.
Our sash brushes, come in a variety of different sizes and are the perfect tools to help make cleaning your engine easier.
Don't let the chemicals dry onto any of the surfaces. If the engine is very hard to reach, with many small intricate areas to clean or it is just a big engine, you may want to divide up the engine into smaller sections to ensure you work methodically.
We recommend only working on a cold engine and when rising off the chemicals, start at one side and work you your way to the other. This will keep the water flowing, preventing the pooling of water. When you have completed this, it is best to use a cloth or air blower to remove the water and dry off the engine. If you have a chamois leather, you could use this to help dry some of the surfaces but don’t use on delicate surfaces like polished metal or paintwork.
One error that some people do is to start their car up and leave the engine running, to let the heat dry it out. Unfortunately, the most important thing to say about this, is extremely careful as sometimes it can cause moisture to build up, which can cause unnecessary damage. We would recommend that you dry the surfaces as much as possible, and leave the bonnet up, especially if you do want to leave the engine running.
Using a Steam Cleaner.
There are three different methods, All of which are described below.
Method 1. Using just the power of steam.
For this method, we would recommend using a brush. Firstly, to loosen the dirt making the process quicker, our sash brushes are an excellent tool for this method.
Start with the underside of the bonnet so that any debris and drips, fall onto the dirty engine, you need to work methodically so that you are not doing things twice. Use the steam cleaner as normal, follow with a brush to loosen the dirt and repeat over the surface until it is clean. Wipe the surface with a clean, damp microfibre towel and then repeat with another one, but this one must be dry.
When you're doing the engine bay, it is best to start at the top and work methodically down, until you have completely cleaned the whole engine bay. Wipe any moisture residue as you go. Once you have completed this, you can dress the engine as normal. For additional advice, please see our guide about, Polishing metal to help protect the metal parts of your engine.
Method 2. Use the power of a degreaser as well as steam.
Firstly, you need to remove most of the heavy grease and grime. As with the first method, it is important to work methodically, starting with the underside of the bonnet.Then spray the APC cleaner/degreaser onto the surface, leave for the recommended time and then use the steam cleaner as normal. Using a brush to help agitate the area, always start with the underside of the bonnet and then, progress to the engine bay. Start from the top and work downwards using a damp towel to wipe away the residue and then follow up with a dry towel to completely dry the area.
Once you have done this, you can dress the engine as normal, for more information see our guide about metal polishes, This gives additional information about how to polish and protect the metal parts of your engine.
Using a steam cleaner will use less water and is a safer method, but it can take longer. However as many homeowners now have a steam cleaner at their disposal, it may be a good way to clean your engine. Of course, your method choice will depend on your vehicle and what equipment you have available.
Cleaning with a hot presser washer, with a steam function.
This is the quickest and most efficient way. By cleaning using water heated above 90oc the high temperatures and rapid water flow help to clean away and dissolve even the most stubborn dirt with ease.
When using a hot pressure washer, we recommend that you use the normal method, as detailed above.
Unless the engine bay is filthy, we recommend that you don't use water heated to above 90oc. This is because with the higher temperatures more is steam is created. This can mask your vision, making it harder to see what you are cleaning
For best results always use a cleaner like an APC, All Purpose Cleaner or Degreaser to help ensure that you thoroughly clean all the areas. For more ingrained and stubborn dirt we recommend using a sash brush to help agitate the dirt first.
Additional reasons why don’t to use water, heated to more than 90oc.
As you are likely to get over spray or splash back when cleaning,which will inevitably go over the paintwork there is the possibility that damage will occur, burning the paintwork.
The cost. You are likely be using diesel to heat the water, even if you use red diesel with its 5% tax it still going to be quite expensive to reach the high temperature you are requiring.
The only time, we would really recommend doing this is if you have removed the engine from the car, so that you can not damage the surrounding parts, however in reality not many people can or will do this.
The reasons why you should not work on a hot or warm engine.
There are endless debates about the apparent advantages of working on a hot or warm engine. Personally we don’t agree, and with this why.
If you spray an APC degreaser or other product onto a warm or hot engine, it will start to evaporate and dry onto the surface. This could potentially be quite dangerous and not say a waste of product.
The products you are using will dry quickly onto the surfaces, meaning you will have less time work the product in. This may also affect the effectiveness of the product if the manufacturer recommends that the product you are using needs to sit on the surface to optimise its cleaning ability.
It is also important to appreciate that some chemicals can come ineffective when exposed to high heat. For example, with normal household bleach, if you add hot water to dilute the bleach, it will lose all its germ-killing properties.
So we would always recommend you work on a cool engine. You are also much less likely to cause an injury, from burning yourself on hot metalwork.
And of now, of course, the best bit: Dressing the engine to help protect the parts and also enhance the appearance of the engine bay.
You will need to consider which sheen you would like applied to your engine, natural satin or a more glossy finish, as this will determine which product or products you will use.
We don't recommend using aerosols to dress your engine, as they normally have a solvent or silicon base which can harm, or dry out surfaces like the rubber hoses. We find it is best to use a water-based dressing like, 'Hyper Dressing ' by Meguiars.
If you have a steam cleaner, using this can be very effective, especially on older engines. Whereas, using a pressure washer or a hose pipe may be a high-risk method. By using a steam cleaner, you can still use chemicals as normal. Brushes can also be used to help aid the removal of grease, and with the added benefit of water being heated up to 155oc (according to the individual model used), this helps to dissolve the grease and grime on the engine safely.
Our favourite products to use when detailing your engine
Meguiars Super Degreaser | Meguiars All Purpose Cleaner | Meguiars Hyper Dressing
Some chemicals may react adversely with the heat, so please read manufacturer's instructions before use, and test the product in an inconspicuous area first.