How to Clean a Diesel Engine

Some of us may remember the conventional wisdom passed down for years, that you’re not supposed to clean a diesel engine.  Turns out, this isn’t really true – Ford, for example, recommends cleaning their Powerstroke diesel engines and includes written guidelines on how to do it. There are some recommended steps you need to take if you’re undertaking the task. Let’s discuss those.

Steps For Cleaning A Diesel Engine

Most of the steps for cleaning a diesel engine are the same as cleaning a gasoline engine.  Your first step is to manually remove the debris that has gotten trapped under the hood and in the grill. Using a brush can make this a little easier.

The second step is to warm the engine up.  Just run it for 5-10 minutes in order to let the grease and oil loosen up.  This will make the rest of your job easier.

The third step is the most important one - cover the recommended parts.  Typically there are 4-5 underhood items that they want you to cover to make sure excess paper doesn’t get in them. These may include the alternator, power steering filler, air intake, and sensors. Just cover them in plastic baggies and secure them in place with rubber bands.

Fourth step – apply your engine degreaser.  If you apply it from the bottom up, you can avoid the annoyance of having cleaner dripping on you.  Let the cleaner sit for 3-5 minutes, depending on how dirty the engine is. Then, take a long-handled brush and scrub down all hard to reach parts or parts that are particularly dirty.

Fifth step – rinse it all off. This is where you want to be careful not to use any kind of high pressure spray.  Car detailers recommend just using a simple water stream from your hose, not a spray. 

Final step - let dry.  As with gasoline engines, you can wait a few minutes to let some of the heat from the engine evaporate the water. But to avoid spotting, you’ll want to finish the job manually.

Some extra tips for cleaning your diesel engine

For the degreaser, most recommendations are to use a water-soluble or citrus-base degreaser. But then again, some people swear by simple, diluted Dawn dish detergent..... Simple Green is brought up as a cleaner people like to use, but it has the potential to damage high strength steel, aluminum, and titanium, as well as damaging electrical connections, because of a hydrogen embrittlement phenomenon.  The hydrogen inside the cleaner can make those materials brittle over time.  You also don’t want to use a high alkali cleaner like Formuila 409 or Fantastic.

Good luck and may a clean engine be with you.

You may be interested in these other posts on diesel engines:

• Are diesel fuel additives worth it?
• Boat diesel - what you need to know
• Did You Know There’s Water in your Diesel Fuel?