How to Maintain Your Impact Wrench for Longevity and Performance

How to Maintain Your Impact Wrench for Longevity and Performance

An impact wrench, also known as an impactor or air wrench, is a powerful pneumatic or electric tool that delivers high torque output in short bursts for tasks like loosening tight bolts and nuts. Impact wrenches rely on concussive blows to turn stuck fasteners that other tools struggle with. They are indispensable tools for automotive repair, construction, manufacturing, and maintenance applications.

Proper maintenance is crucial for ensuring an impact wrench continues delivering the high performance you depend on over years of use. Neglecting maintenance can lead to costly repairs or replacement when the tool fails prematurely. This article will overview key impact wrench maintenance tips to extend its longevity and keep it operating like new. We'll cover regular cleaning, lubrication, inspecting parts for wear, replacing brushes, gearbox care, air filter changes, proper storage, and safety. With some basic routine care, your impact wrench will provide reliable service for the long run. Read on for maintenance best practices to maximize the lifespan of this hardworking addition to your toolbox.

Regular Cleaning

Keeping your impact wrench clean is one of the most important maintenance tasks. After each use, you should wipe down the tool to remove any dirt, grease, metal shavings or other debris. Use a damp cloth to carefully clean the outside housing and handle. Pay extra attention to the air vents, chuck, and any other openings where dust can collect.

You should also do a more thorough cleaning periodically, such as every few months. Disconnect the air hose and use compressed air to blow out the interior, especially the motor and gearbox. An old toothbrush can help scrub away caked-on grease, dust and grime. Some mechanics recommend spraying brake cleaner or electrical contact cleaner into the air vents while blasting compressed air through to help flush out the insides. Just be sure to do this cleaning in a well-ventilated area.

Regular cleaning keeps your impact wrench running smoothly by removing abrasive particles that can damage internal components over time. It also improves ventilation and prevents overheating. For tools like the Milwaukee MILM18BIW120 Cordless Impact Wrench, proper maintenance is crucial. This model benefits significantly from frequent cleaning to maintain its high performance. Storing a dirty tool between uses will allow moisture, dirt, and debris to accumulate, leading to corrosion and premature wear. Taking the time to wipe it down and clean out the air vents after each use goes a long way toward extending the life of your impact wrench.


Properly lubricating your impact wrench is crucial for longevity and performance. The moving parts like the hammer mechanism and anvil need lubrication to prevent wear and friction buildup.

You'll want to use a lightweight machine oil or impact wrench lubricant to lubricate the interior parts. Avoid regular motor oils as they can be too thick. The owner's manual will specify the type of lubricant recommended by the manufacturer. Lightly coat the interior parts with oil every 25 hours of use or more frequently if you use the tool heavily.

The hammer mechanism and anvil are key parts to lubricate regularly. Put a few drops of oil into the air inlet so it reaches the interior. Also lubricate any gears, bearings, the ratchet mechanism, and other moving components according to the manual.

Exterior parts like the trigger and housing just need occasional lubrication to prevent rust. Wipe down the outside with a rag and apply a thin coat of silicone or lithium grease.

Proper lubrication will keep your impact wrench running smoothly for years to come. Don't overlook this important maintenance step.

Inspecting Parts

It's important to periodically inspect your impact wrench for any worn parts that need replacing. Pay particular attention to the anvil, hammer mechanism, and grip.

The anvil is the section at the front of the tool that grips onto sockets and attachments. Check for excessive wear or chips on the anvil, as this can cause it to lose grip and slip off sockets. Replace the anvil if badly worn.

Examine the hammer mechanism inside the housing. This is the part that provides the hammering action for breaking loose tight bolts. Look for worn or cracked hammer components. If the hammer isn't striking properly, it likely needs replacing.

Also inspect the grip and trigger areas. Make sure the rubber grip hasn't become loose or torn, which could cause you to lose control of the tool. Check for any worn parts around the trigger that could prevent smooth operation.

While inspecting, tighten any screws, bolts, or fasteners that may have become loose through prolonged use. Loose hardware can lead to unstable and unsafe operation. Periodically go over the entire tool and tighten any parts that wiggle or have play in them. This will help keep everything tight and minimize vibration.

Replacing worn parts as needed will keep your impact wrench running in top form for longer. Periodic inspection and maintenance is key for longevity and performance.

Replacing Carbon Brushes

The carbon brushes in your impact wrench connect the electric power to the motor and need to be inspected and replaced periodically as they wear down. Checking the brushes every 6 months or so and replacing them when they get to less than half their original size is recommended.

Replacing the brushes is a relatively straightforward process:

  • Unplug the impact wrench and remove any battery pack if it's cordless.
  • Locate the brush caps on the tool's housing and unscrew them with a screwdriver to access the brushes.
  • Carefully remove the old brushes from their slots. Make note of their orientation.
  • Insert the new brushes in the same direction as the old ones. Make sure they slide freely in their slots.
  • Replace the brush caps and screw them back in place.

When installing new carbon brushes, be sure to use brushes specified by the manufacturer. Using lower quality generic brushes can lead to reduced power and premature wear. Genuine replacement brushes matched to your model will ensure optimal performance and extended service life. For example, the SeeSii WH700 Brushless Cordless Impact Wrench should use only high-quality brushes designed for its powerful brushless motor to maintain its high torque output and efficiency.

Gearbox Maintenance

The gearbox is one of the most important parts of an impact wrench as it contains the internal gears and bearings that translate the motor's power into torque. Proper maintenance of the gearbox is critical for longevity and performance.

Check oil level and quality in gearbox

  • Check the oil level in the gearbox periodically to ensure there is enough lubrication for the gears. Consult your owner's manual for how often to check it. Some may have a sight glass or dipstick to check oil level.

  • Make sure the oil is clean and free of metal debris or contamination, which can indicate wear on internal parts. Change oil immediately if it looks dirty.

Change oil periodically as specified

  • Oil breaks down over time and loses its lubricating properties. Change the gearbox oil based on the intervals specified in your owner's manual, usually every 50 hours of use or so. Use oil weight and type recommended by the manufacturer.

Grease gear teeth if required

  • Some impact wrenches may have grease ports to lubricate the gear teeth directly. Pump grease into the ports periodically if your tool has them. This provides added lubrication between the meshing gear teeth.

Replacing Air Filter

Replacing the air filter regularly is one of the most important maintenance tasks for an impact wrench. The air filter cleans the air that enters the tool, preventing dust and debris from being ingested into the internal mechanism. Over time, the filter can become clogged with particulates, restricting airflow and reducing performance.

It's recommended to replace the air filter every 3-6 months or after about 50 hours of use. Refer to your tool's manual for the specified interval. Make sure to use an original or compatible replacement filter to maintain proper airflow. Aftermarket or low-quality filters may not filter as effectively.

Replacing the filter is quick and simple in most models. Locate the air filter housing, unclip or unscrew it, and slide out the old filter. Insert a new filter, replace the housing, and you're done. Improved airflow will restore top performance and help prevent premature wear on internal parts. The small effort of regular air filter changes helps ensure your impact wrench delivers reliable service for years to come.


Proper storage of your impact wrench is crucial to maintaining its performance and extending its lifespan. When not in use, be sure to store your impact wrench indoors in a clean, dry place. Exposure to moisture, dirt, dust, and other contaminants can lead to corrosion, clogged air vents, and internal damage over time.

For cordless impact wrenches, disconnect the battery before storage. Lithium-ion batteries can slowly self-discharge when left idle in the tool. Storing the battery separately prevents this and keeps the battery fresh. Check the battery charge every few months and recharge as needed.

Avoid storing your impact wrench in extremely cold or hot temperatures if possible. Temperature extremes can reduce battery life for cordless models. For any impact wrench, cold conditions may cause lubricants to thicken while heat can degrade seals and gaskets. Storing at moderate room temperature is ideal.

Keep your impact wrench in its case or another protected area when not using it. This shields it from dust, dirt and potential impacts from other stored tools or objects. Proper storage keeps your impact wrench performing like new for years to come.

Safety Tips

When using and maintaining your impact wrench, following some basic safety tips can help prevent accidents and injuries:

  • Wear safety goggles to protect your eyes from debris that could be thrown from the tool. Impact wrenches can eject small parts or particles at high speeds.

  • Ensure you have stable footing when using your impact wrench. The torque from the tool can cause you to lose balance if you are not firmly planted. Stand with a solid base and don't overextend your arms.

  • Maintain a firm grip and control of the tool at all times. Impact wrenches have powerful torque that can twist out of your hands if you aren't holding on properly. Use both hands if needed.

  • Always unplug the impact wrench before changing parts or servicing it. Accidental starts could cause injuries if your hands are near moving parts. Make sure it's unplugged before doing any maintenance.

Following basic safety precautions like these will help you use your impact wrench without injuries. Be aware of the hazards and take measures to protect yourself.

When to Seek Professional Help

It's generally recommended to seek help from a professional repair technician for major issues with your impact wrench rather than trying to fix it yourself. Here are some signs it's time to take your tool for professional service:

  • Major repairs or breakdowns - If your impact wrench stops working entirely, starts making odd noises, loses power, or has other serious malfunctions, it likely requires professional repair work. Attempting major repairs yourself when you're not an experienced technician could make the problem worse.

  • If improper maintenance leads to issues - Neglecting regular maintenance like lubrication and cleaning can allow dust, dirt and debris to build up and cause eventual tool failure. If you haven't been keeping up with proper maintenance and now have problems, it's best to have a repair technician service it.

  • For calibration if accuracy/precision declines - Impact wrenches are calibrated for proper torque settings from the factory. If you notice your torque accuracy declining where fasteners are under or over-tightened, the tool likely needs recalibration by a professional.

The costs of professional impact wrench service will vary based on what repairs or maintenance is needed. But it's worth the investment to keep your tool functioning optimally and avoid causing bigger problems from improper DIY repairs. The professionals have the expertise to get your tool back up and running its best.