How To Clean Your Subaru Forester’s Engine

By Nick Marchenko, PhD

Updated: July 27, 2023

The engine of the Subaru Forester serves as the pulsating heart that governs acceleration, velocity, and overall driving pleasure. Adhering to a proper engine maintenance routine is key to its long-lasting performance and prevents any potential mishaps.

With everyday use, the engine progressively accumulates grime; dust and debris attach to it, and evidence of lingering lubricant, coolant, or other contaminants might surface in diverse places.

This muck doesn't just diminish the engine's aesthetics and lessens its appeal due to the extensive mixture of foreign dirt and contaminants, but it could also impair its efficiency. 

For instance, an engine heavily coated in filth can overheat effortlessly as the heat transfer mechanism is disrupted. Besides, a dirt-ridden engine makes it challenging to discern exterior symptoms of malfunction, such as a fresh oil leak or fissure.

Therefore, it's crucial to look after your Subaru Forester in every aspect: from its outer shell (car's body) to its innards (interior, engine bay, etc.).

It's advisable to give your Subaru Forester engine a good cleaning at least once in a few years. However, this engine cleansing routine should be performed more frequently if you reside in an environment persistently bombarded by dust, grime, and sand.

CAUTION / ATTENTION:

Engine washing of the Subaru Forester is a complex procedure that necessitates taking numerous factors into account. An improper execution of this process could lead to total engine collapse or a costly repair job.

Therefore, to avoid running into such extremes—we provide a comprehensive guide on how to do it, but that doesn't eliminate the risk of user error.

If you need further explanation, or if you have any hesitations about washing the engine yourself, it's always safer and more efficient to delegate this job to professionals who can get it done promptly and securely.

Is it necessary to wash the Subaru Forester's engine?

New Subaru Forester owners often ask about the necessity of engine washing. Opinions among motorists regarding this matter are varied.

The accumulation of dirt and clinging dust negatively impacts the performance of the motor, leading to:

• deterioration of heat transfer;
• reduction in power;
• increased fuel consumption;
• the risk of spontaneous combustion.

Upon evaluating these risks, it becomes apparent why washing the engine is a good idea. However, there's no strict periodicity for this procedure.

It really depends on the intensity of vehicle usage, how you drive your vehicle, and its unique design features. Cleaning the engine only becomes necessary under certain circumstances:

• serious motor contamination due to the failure of pipes, seals, and other similar components;
• determining the source of fluid leaks;
• preparation of the car for an overhaul or sale.

What do you need to clean your Subaru Forester's engine?

Before embarking on an engine cleaning adventure, understand that it demands responsibility, patience, and a keen eye. Also, make sure you have all the necessary items with you beforehand. These items include:

• Electric contact spray;
• Brush;
• Rag(s);
• WD-40;
• Hose or high-pressure washer;
• Car shampoo or degreaser;
• Polyethylene bags;
• Duct tape;
• Hose for blowing with compressed air.

How to clean your Subaru Forester engine?

It's best to wash your engine under favorable weather conditions. Opt for a day that's warm but not scorching, without rain or wind. The ideal time for an engine clean-up is after the winter, when dirt tends to accumulate on and under the engine.

Warm up your engine

Before cleaning, a light engine warm-up is necessary to make dirt removal easier.

Note: Avoid washing the engine when it reaches its working temperature - 100 degrees - as this can be excessive. If cold water comes into contact with a hot surface, it may damage the engine or its components.

Don't wash the engine if you've recently completed a long journey in your Forester. Allow it to cool down for around one and a half hours.

The optimal approach is to start the engine when it's "cold", wait until it warms up to 60-65 degrees, then turn it off and let it sit for about 15 minutes. This way, your Subaru Forester's engine will reach the ideal temperature for cleaning.

Disconnect the negative battery terminal

Start off by disconnecting the negative terminal from the car battery. This way, you're de-energizing the entire electrical system of your Forester, and even if water happens to touch some electrical components, there won't be a short circuit.

For best results, completely remove the battery from the car after disconnecting both terminals. 

If your Forester has features that make disconnecting the negative terminal a challenge, remember, your first priority should be to disconnect this negative terminal.

Manually remove large debris from the engine compartment

It's common to find dirt and debris like tree fluff, leaves, or grass gathered under the hood. So, before launching into the cleanup process, manually remove these contaminants. They tend to be lodged in the tiny crevices of the engine bay or closer to the interior. Diligently inspect these areas and clear away any dirt.

Cover up all electronic contacts

Electronic components, sensors, and wires are especially sensitive to water. Even if the system is de-energized during washing, water can still pose a threat.

Without proper care, contacts may oxidize, potentially leading to electrical malfunctions. The tricky part is that this oxidation may occur not immediately but after some time. This could mean unexpected troubles when you least expect them.

Before you start washing the engine, safeguard each electrical contact under the hood that could be affected by water. These include:
Sensors (pay special attention to these);

• Wires;
• Headlight contacts;
• Under-the-hood fuse block;
• Any visible electronic contacts under the hood

Here are two trusted methods to protect these contacts:

• Apply a special spray that keeps contacts dry;
• Enclose contacts with polyethylene bags or film, and use duct tape to prevent water from reaching them.

It's advisable to use both methods. The special spray creates a protective layer, "sealing the contact," to prevent water penetration. Then, enclose these contacts in polyethylene bags and secure them tightly. Insulation tape is quite handy for this so the package won't come undone.
 

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Use a polyethylene bag and duct tape to secure the fuse block. Ensure all contacts are properly covered. If you're uncertain, refer to your Subaru Forester's wiring diagram.

Other vehicle components should also be isolated to prevent water from getting in. Look for any gaps in the air supply system where water might infiltrate.

If your car has a carburetor, wrap it in a bag to prevent water from entering - water inside the power system could disrupt the engine's functionality.

Apply the degreaser or car shampoo to your Subaru Forester engine surface

Time to apply the washing agent to the engine surface. Make sure every nook and cranny is covered with either cleaning shampoo or degreaser. No need to go overboard with the quantity here.

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Let cleaners perform their task

Once the cleaners are applied to the engine surface, let them do their magic by breaking down the dirt and contaminants. Give it a good 3-6 minutes to soak in.

Proceed to manual engine cleaning

Once enough time has passed, it's time to roll up your sleeves and start the manual cleaning procedure. Depending on the type and degree of grime, grab a brush or rag, and start cleaning your Subaru Forester's engine.

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Be meticulous and gentle to prevent any damage. And don't forget, the exhaust manifold might still be hot, so be careful not to burn yourself.

If you encounter stubborn contamination, give WD-40 a try. This versatile tool can handle a range of cleaning tasks, including removing rust and ingrained dirt. Simply spray WD-40 onto the contaminated area, let it work for a bit, and then start scrubbing.

Rinse your Subaru Forester's engine

Once the manual cleaning is done, it's time to move on to the final stage: rinsing the engine with water.

For this step, keep the water pressure as low as possible (if you're using a high-pressure washer) to avoid damaging the engine bay.

Wash carefully but thoroughly to wash off all the chemicals. Ensure that no cleaner is left on the engine surface as it might cause stains.

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Blow out all electrical contacts with compressed air

Despite your best efforts to protect your engine's electronics from water, nothing is foolproof.

To protect the contacts from potential corrosion, once you've removed the protective packaging, they should be blown with compressed air. This will ensure that even if a few water droplets have landed on the contacts, the blast of high-pressure air will dislodge them.

Dry the engine and its components thoroughly

After you've finished washing, don't forget to thoroughly dry the engine. You can use paper towels or dry rags for this.

Give every part of the engine compartment a thorough wipe. If any water has splashed onto the electrical contacts, dry them off as well.

Now, remove the protective plastic bags and duct tape. Carefully inspect every part of the engine bay to ensure it's dry and clean.

Once you've reconnected the battery terminals, start your Subaru Forester to make sure everything's working correctly.

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Can I clean the Subaru Forester engine at a car wash?

Washing at a car wash can often stir up apprehension for many Subaru owners, particularly those who are new to the game. The strong water pressure and chemicals used are excellent for cleaning the car body and other areas where there's no risk of dislodging contacts or pipes or blocking technical crevices.

However, for the space under the hood, this method can seem ineffective or even detrimental. The challenge lies in reaching those hard-to-get-to places without causing short circuits, soaking the air filter, or displacing sensors and nozzles.

In reality, washing your Subaru Forester engine at a self-service car wash can be a bit of a tall order, given that you're limited to using the tools available on site.

Professional detailing centers, on the other hand, offer specific services designed to provide either a thorough or superficial clean of the space beneath the hood. But even here, things can get complicated. The quality of the wash will depend on the technology, equipment, and chemicals used.

Options for washing Subaru Forester’s engine at a car wash

The options for washing your engine at a car wash vary, with each company offering different services, but the end results should be similar:

Surface wash. This method is akin to a regular car wash. The mechanic pops open the hood, sprays a foam solution over the area, and then rinses it with water. This leaves you with an engine that looks clean, at least on the surface.

Thorough washing. This option takes more time to prepare for and offers a higher level of cleanliness. The cost of this service may be comparable to, or even exceed, the cost of a body wash.

All surfaces are meticulously cleaned, with dirt removed from even the most inaccessible areas, often by hand, using sponges, rags, and brushes. Some parts might be taken apart to facilitate the cleaning. When it's all done, your engine compartment will be spick and span, just like it was when it left the factory.

To Sum Everything Up

Engine washing may seem like a trivial task, but that couldn't be further from the truth. Getting rid of any dirt, dust, grease, and debris from the engine surface and its components is a critical aspect of proper Subaru Forester maintenance.

Before you start washing, it's important to protect any vulnerable components, such as the wiring, contacts, and fuse box, to prevent them from coming into contact with water and chemicals. 

Proper and meticulous engine bay cleaning helps promote better cooling, prevents corrosion of the components, and ensures that everything under the hood is properly cleaned and remains in good condition, thereby enhancing the longevity and optimal performance of your Subaru Forester.