Engine Bay Cleaning

The Nitty Gritty:

Undercarriage, Engine, and Plastic Trim Cleaning

Lesson 2

Undercarriage Cleaning

                While the undercarriage of the vehicle is not something that will need to be cleaned very often it is still a very useful skill to have and one that is worth mastering when it comes to running a mobile auto detail business.

                You will spend more time cleaning the wheel wells and front and rear suspension components on SUVS and Trucks then the undercarriage, but the same techniques used in these areas applies to the full undercarriage of the vehicle. Typically, I upsell the undercarriage cleaning during the spring after the salt from the roads over the winter time or for my Off-road enthusiast and Hunting customers who take their rigs out to properties and get all sorts of dirt on the underside.

                Why perform and undercarriage cleaning? Dirt traps all sorts of elements and when it adheres to the frame of a vehicle it can inhibit rust which will denigrate the frame of a car very quickly. When it comes to SUVs and Trucks, the undercarriage and wheel wells are fairly noticeable especially on lifted vehicles. If you perform a nice detail on a car but leave dirt and dust visible on the wheel wells and exposed framing you are doing your detail service injustice and the eye will naturally drift towards the dirty areas rather then focus on the nice and beautifully cleaned vehicle.

Undercarriage Wash

                Start by performing a good undercarriage wash. I recommend taking care of the undercarriage before you move to the body of the vehicle as you will just overspray water and soap onto clean paint, which will require double work to clean.

When it comes to cleaning tight areas I like to use the Snubby by Chemical Guys. This is a short wand attachment for your pressure washer that allows you to get into tighter areas without having to manage a long nozzle. Of course, it is not required but helpful.

Mix some Solution with your favorite PH balanced soap into your foam cannon. Lucratively spray the undercarriage first and let the product sit for about 2-minutes. Using a brush set that is specific for these heavy builds up areas, clean any areas that are easy to reach with a brush. Typically, this includes the front and rear suspension components, wheel wells, and left and right frame bars.

Thoroughly rinse the area and inspect. If you still have some heavy build up you can use a 50/50 mix of your solution product and water to spray and re-brush those areas and then final rinse. The undercarriage is not complete. You can always get very detailed here and get every nook or put the car on a lift to really get it cleaned, typically this is reserved for show cars and only done at a shop not in a mobile setting.

Money Saver-Solution is type of degreaser that is safe to use on various areas of a vehicle and can be used both inside and outside of the vehicle. It is my go-to product for heavier cleaning on grease and grime. However, if you want to save even more money you can create your own degreaser mix by using dawn dish soap and water and diluting to the desired strength. Dawn is a great degreaser product and is safe to use on plastic and vinyl and will not cause rusting if not fully rinsed properly. Pro Tip: Always keep a small bottle of dawn dish soap on hand. You will find we bring up several ways it can be used during the detail process.

Undercarriage Spray 

Now that you have the undercarriage and wheel wells nice and clean you want the results to last and add some brilliance. There are several undercarriage products on the market that will add a nice rich satin finish to the undercarriage and wheel well components while reducing dirt and dust build up producing long lasting results and making the next undercarriage and wheel well cleaning 10x easier.

Two products I use as an undercarriage spray

  • Shine Supply Classy Chassis-Fantastic product adds a brilliant satin shine and has long lasting results (Typically around 2-3 months).
  • Chemical Guys Bare Bones-This is my go to when I forget to put in an order of Classy Chassis. There are Detail Garage locations throughout the U.S. that are vendors of Chemical Guys products. I can swing by and grab what I need at any one of their locations in a hurry when I run low and forget to restock in time.

Engine Bay Cleaning

Engine Bay is a great upsell, and I always recommend you upsell this car wash add-on. It can be time consuming and requires careful attention during the cleaning process to avoid getting water in areas that can damage electrical components.

Tips: Disconnect the batter completely and remove if possible, prior to cleaning the engine bay. This ensure no power is running to any components in the engine bay and will prevent any accidental short circuiting. This is a rare occurrence even with the battery connected especially on newer cars. However, it is always better to be safe then sorry and it only takes a couple extra minutes.

Cover the alternator and air intake. These two areas can still be cleaned but when you are spraying water into the engine bay to rinse everything off you do not want to jam water into these components.

Engine Cleaner

After prepping the engine bay and ensuring everything that needs to be covered with plastic and protected from water is completed you are ready to clean the engine. You can use the same brushes that you used during your undercarriage cleaning step (Thoroughly rinse brushes after every use to help them last longer).

Spray degreaser diluted 1:1 throughout the engine bay. You can use Solution, Purple, or a Dawn Mix. You will find through trial and error which product setup you prefer. I use solution because again it works as a multipurpose cleaner inside and out saving me time, money, and space.

DO NOT LET THE DEGREASER DRY! Using a brush or taddy towel (any older rag not used on the painted surface of the car, I like to use old microfiber towels) work the solution to break up and remove dirt, grime, and grease. Lightly rinse the engine bay-I don’t recommend a pressure washer be used a good garden hose attachment sprayer is perfect.

You can use a blower, compressed air (if you carry one), or a towel to dry the engine bay.

PRO TIP: Clean the underside of the hood in the same manner, rinse, and dry prior to washing the engine bay. If you do this secondary all the dirt and grime from the hood will fall onto your nice clean engine. Seems obvious…but I have forgotten a few times.

Engine Cleaning Packages

I will go over detail packages in-depth more later, but if you are going to start offering this service now here are the two packages I recommend.

Basic – Simple a rinse, solution spray, and final rinse. This removes roughly 60% of the looser dirt and grime on the engine bay and underside of the hood. It does not take long and also gives you the chance to remove debris such as leaves and twigs in the engine bay to help prevent electrical fires.

                Pricing $25-$35 max
Deep – Rinse, Solution, Detail Brush and Wipe Down to remove all visible grease and dirt, final rinse, dry, and dressing.

                Pricing $45-$75 (Depends on how dirt the engine bay is)

Engine Steam Cleaner

If you are able to invest in a vapor steamer (which I highly recommend) you can use it to clean areas of the engine bay that have stubborn build up. Only use a vapor steamer on the metal components. Often the vapor steamer is to hot and will remove the paint from the inside of the engine bay painted surfaces if you are not careful. It took me 2 years to be able to afford a quality vapor steamer so do not worry if you do not have one at first. We will go over its benefits and uses and where it will save you time and make you money, but you can definitely get away with a high-end detail without one.

Best Engine Cleaner

As mentioned before I personally prefer solution as it does a fantastic job and it is a emulsifier. This means it “loosens” dirt and grime and is safe on multiple surfaces, including leather. A fantastic product all around. You can find out more about it on the Shine Supply website. If it does not seem to work the first time reapply and agitate with a brush.

Plastic and Trim Cleaning

Here is a good eye sore, especially on vehicles that see daily road use. Plastic trim fades quickly and is very difficult to restore. You have two options when it comes to cleaning trim and plastic. You can pressure wash it and use solution and a brush to remove oxidation and build up on the plastic, then coat with a trim conditioner. Or after cleaning the trim you can use a trim paint to recoat the trim and bring back protection and even shine.

                Trim Restorer-You have seen products such as Back to Black as it is sold in every auto supply retailer. This product removes light oxidation and grime build up while leaving a protective coating. It does not last for very long and really is more useful as a preventative tool then a restorer tool.

To restore trim during the washing process you can pressure wash the trim-be careful if the trim is brittle-use solution and a brush to break up dirt, grime, and oxidation and leave the trim tacky and clean ready for product.  


                Plastic Trim Paint-This is my go-to for all trim that is faded. After cleaning the trim components and completing my wash of the entire body I will use 3M 1” masking tape and tape below and above the trim. Try to get the tape as close to the trim as possible if not right next to it. 1” masking tape is more flexible and a great way to follow the run of trim. You can follow with a 2” masking tape to overlap and give yourself greater surface area to protect the paint from your trim paint.

I use Shine Supply Trim Paint which comes in both grey and black. Follow the link to also get the proper applicator pad for the product. Shake your bottle well and apply in a shaded area for best results. Apply a light even layer to the trim and let fully cure (only takes a couple of minutes). Come back and apply a second coat to deepen the shine and color. The paint actually will fill the pores of the trim and restore color to the trim. It is great for the plastic bumper components as well as bed railing on trucks or roof racks.

As with any new product test in a small area to get comfortable with the application process.

Trim paint offers long lasting results and is the only product I use to properly restore faded plastic and vinyl trim on vehicles. A bottle of this product will last for 6-8 full trim restoration projects giving you roughly a 200% return on your investment.

                Pricing $50-$100

That’s its for this lesson. These are great add-ons for any detail package and can help create some extra cash flow from projects with a minimal amount of added time.

I will see you in the next lesson.


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