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Posted on: 29 February 2016

If you have recently purchased a used motor from a salvage yard, it may have a lot of grime and rust on it. Before you start working on the internal workings of the engine, you may want to clean it up so you can get a better idea about its external condition. To do this, use the following two-step guide to remove the dirt and rust from the surface, casing and bolts.

Step 1: Use A Wire Brush And Sandpaper To Remove Excess Surface Rust

The first step in cleaning your motor's exterior is to use a wire brush to remove the excess surface rust, especially in areas where there is a thick layer of oxidation. Knocking off this top layer prepares the bolts and casing for the next two steps.

When using the wire brush on flat areas, use small, circular motions to scrub the rust off the metal. Use firm, even pressure when doing this to avoid gouging the metal with the metal bristles. Instead of only holding the brush by the handle, place both hands above the bristles so you have better control of the brush.

While cleaning around the bolts, place one hand above the bristles, and go around the sides of the heads first. This allows the bristles to clean the junctions between the heads and casing, making removing the bolts in the next step easier. 

After you have finished brushing the excess rust, blow it off of the motor. If you have an air compressor, use this to blow it away from the motor. If you do not have one, a can of compressed air can also work. Just make sure you hold the nozzle no more than an inch from the surface to achieve maximum pressure for cleaning the rust off.

Once you have removed the top layer of dust, sand the surface with fine-grit sandpaper. This will remove any remaining rust on the surface of the casing. However, do not use the sandpaper on the bolts, as this could weaken them. Instead, go on to the second step.

Step 2:  Remove Rusty Bolts And Soak Them In White Distilled Vinegar

Now that you have removed the rust from around the bolts, remove them with a socket wrench so you can clean the threads as well. If you have trouble, spray a small amount of silicone-based lubricant under the heads, and wait for a few minutes. This should loosen the bolts up enough for you to remove them without breaking them.

Once you have all of the bolts removed, soak them in straight white distilled vinegar. The active ingredient in vinegar is acetic acid, which is weak enough not to harm your engine's metal but strong enough to cut through the oxidation. Do not use vinegar on other parts of the motor. Although it is safe for the metal, you do not want residual vinegar to run inside the engine and contaminate the oil or coolant.

Soaking the bolts for about an hour should loosen the rust enough so you can remove it with a clean, lint-free cloth. A mechanic's cloth is ideal because the fabric is smooth and will not snag on the threads.

Once you have wiped the rust off of the bolts, set them aside to air dry without rinsing them. 

Using the above guide will help you get rid of the surface rust on your used motor, allowing you to visualize it better. However, if you run across other damage to the casing or a patch of stubborn rust, you may want to contact the salvage yard or a used auto parts store for advice on how to proceed.