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How To Properly Clean Your Car's Engine

Engine cleaning

Cleaning your car's engine is not as easy as just hosing it off. First, hitting a hot engine with cold water could create some problems as the metals suddenly (and unevenly) change temperature. Worse, however, not cleaning your engine properly and while keeping in mind legal requirements for dumping chemicals could mean trouble.

Be sure to be in a proper location with the ability to capture and properly dispose of the wastewater from your cleaning. Be aware that even the "foaming" engine cleaners and similar products will have runoff.

To begin with, you will need some tools and products. Which ones will depend some on how dirty your engine is and what it's coated with (oil, grease, general road sludge). Most likely your engine, if you're worried about cleaning it, has a mixture of oil and road sludge coating various parts of it.

We recommend starting with a good set of grease-busting cleansers such as Simple Green, The Works, etc. Some parts may be cleaned with CLR or other harsh chemicals, but you should know for sure that the part is able to remain unharmed before using a product. You will need brake cleaner and simple scrub brushes (non-metal bristles) and dish soap as well.

Begin by disconnecting the battery cables, starting with the negative side (so you cannot short the circuit). Before tying off the terminals to a safe location so they do not accidentally touch anything and create a circuit, be sure to scrub the terminals well. There are special metal bristled scrubs for this job or you can use a toothbrush-sized scrubber with metal bristles. Thoroughly clean off the corrosion on both the cable ends and the terminals on the battery. Now remove the battery so you can clean the tray it sits within, especially underneath the battery where the battery's chemicals may have leaked and caused corrosion. The same wire brush used on the battery terminals can be used here, though if it's a metal tray, a few squirts of CLR or similar chemical may also do the job well. Now is a good time to consider replacing posts/cable ends if they look like they could use it. You should also replace or thoroughly clean the hold-down bolt for your battery and its bracket.

Using plastic bags (garbage or grocery sacks doubled up work well), cover up electrical components like the alternator, computer/ECM, and relay box(es). They don't need to be waterproofed, but your covers should keep most of the water away as you spray down the engine later.

If you have access to compressed air, use it to blow out dust and debris from the engine compartment. If you do not have this, carefully use a shop vacuum with a narrow nozzle to do the same.

If you're using degreaser, you may now coat the relevant parts of the engine block, heads, exhaust manifolds, etc. and let it soak in to do its job. If you're using something else, such as Simple Green with hot water, spray that on under pressure, if possible, or simply spray it on, let it soak for a while, and then rinse it off and repeat.

Finally, CLR and a heavy brush (wire is OK, but stiff bristled plastic is safer) do wonders for aluminum parts like your heads, power steering pump, etc.

To get to hard-to-reach spaces, use brake cleaner with a nozzle to spray in with the can's pressure. This will get most of the grease out and doesn't leave residue behind. A blast with some water pressure to rinse usually finishes off whatever's left.

Last but not least, use dish soap and a thick sponge followed by a plastic bristle brush to clean off plastic parts and covers.

Once everything is dry, put it all back together, re-install and connect the battery, and start the engine. It should run smoothly. Before it warms up, now may be the time to add dyes to the various fluids to check for leaks and do pressure tests.

If you have access to a lift, many of these techniques can be used on other parts of the car.