How To Service a Pressure Washer Muffler and Spark Arrestor

Updated: May 26, 2023

Got a pressure washer that's too loud, or isn't running at full power? The muffler and spark arrestor could be responsible.

A little mechanical knowledge can go a long way, especially with a gas-powered pressure washer. A basic understanding of the most important parts of your pressure washer, how they work and how to maintain them, keeps you washing longer with fewer trips to the repair shop.

Like all internal combustion machines, gas-powered pressure washers feature lots of parts that work together for smooth operation. Some are well-known to DIYers, others less so. Two parts that probably don’t get enough attention are the muffler and spark arrestor.

Their names suggest their jobs. Mufflers dampen engine noise, and spark arrestors prevent sparks from shooting out with the exhaust and possibly starting a fire. Both need to be in good condition for your pressure washer to operate safely.

I once used a beat-up old Honda pressure washer to clean the walls of a backwoods cabin, and was astonished at how loud it was. Even with hearing protection, it was ear-splitting. Turns out the muffler rusted so much it had a huge hole in the back. After swapping in a new muffler, the difference was like night and day. I never underestimated the importance of mufflers again.

I’ve personally never had any issues with spark arrestors, but I know what happens when they need servicing. Keep reading to learn what to look for when these two key components malfunction.

Signs Your Pressure Washer Muffler and Spark Arrestor Need Servicing

The first step is learning the signs your pressure washer muffler or spark arrestor might be failing.

Pressure washer muffler

The muffler is a rounded metal bulb within a protective rectangular metal shroud near the bottom of the engine. Look for it where the exhaust gases exit the machine.

Pressure washer mufflers have only one purpose: making the engine quieter. You’ll know yours isn’t working properly if it’s extremely rusty and the engine seems noticeably louder.

Corrosion is generally the culprit here. Pressure washer mufflers and their metal shrouds heat up while the machine runs. Over time, this heat, combined with over-spray moisture from the washer, leads to rust, which eventually leads to holes.

Pressure washer spark arrestor

Pressure washer spark arrestors are small discs of fine metal mesh that fit in the exhaust port of the muffler. Not all pressure washers come with a spark arrestor, but those that do may malfunction in a specific way.

Carbon buildup can partially clog spark arrestors. When this happens, your washer can’t vent enough exhaust gases to run properly. You’ll notice the engine can’t rev up to full power, and the washer sprays water less forcefully. You may also see blackish smoke from the exhaust port, or notice the muffler is much hotter than usual. In extreme cases, your pressure washer won’t run at all.

How To Service Your Pressure Washer Muffler and Spark Arrestor

Tools and supplies

  • Socket wrench set (probably a 10-mm);
  • Penetrating oil;
  • Small wire brush;
  • New muffler.

Remove the outer muffler shroud

  • Locate the muffler shroud near the bottom of the engine.
  • Take a socket wrench and loosen the bolts holding the shroud in place. Apply penetrating oil around the bolt heads if they’re stuck due to corrosion.
  • Remove the outer muffler shroud and place it to one side.

Remove the muffler

  • Loosen the bolts holding the muffler to the pressure washer. Apply penetrating oil if they’re stuck.
  • Remove the muffler and examine the exhaust port. Look for a cylindrical piece of fine metal mesh in the port. This is the spark arrestor. If there’s nothing there, your pressure washer doesn’t have one.

If you have a spark arrestor:

Clean the spark arrestor

  • Remove the spark arrestor from the muffler, then use a small wire brush to clean out carbon buildup or other debris.

Replace the muffler

  • Examine your muffler for substantial rust and holes. If you find either, purchase a new muffler that fits your pressure washer. (Amazon has a great selection.)
  • Place the cleaned spark arrestor in the new or undamaged old muffler.
  • Install the muffler, then replace the protective metal shroud. New mufflers usually come with matching protective shrouds, so you probably won’t need to buy each item separately. If you’re replacing the muffler, you should replace the shroud too, even if might have a little life left.
  • Start up your pressure washer to make sure it runs properly.