Service Tech Training: Doing Pump Oil Changes

By Gary Weidner / Published November 2015

Editor’s Note: This service technician training series was published previously from September 2008 through June 2014 in Cleaner Times|IWA. It is being republished with the recognition this material is not exhaustive of the subject at hand, but rather to present to new servicepeople an all-important fundamental understanding of how things work.

Even if (or maybe especially if) you’re relatively new at servicing pressure washers, you’ve probably been assigned to do some oil changes on the high pressure pumps. Now that doesn’t strike me as the world’s most interesting task. Kind of reminds me of a time when I worked as a painter—seems like the newer painters always got the most tedious assignments like painting radiators or the insides of small closets.

We want ways to change oil that are both easiest for us and have the least chance of leaving puddles of oil on or under the customer’s machine. Below I’ll cover four methods: draining, suction gun, hand suction pump, and electric suction pump. Don’t forget that the warmer the oil, the more easily it will come out, regardless of the method. Try to do the oil change after you’re done running/testing the machine.

Draining

Andy Rooney would have a field day describing what it’s like to drain the pump oil on many pressure washers. Although some of the manufacturers have improved their designs over the years, sometimes it seems like the pump and machine manufacturers have conspired together to see how difficult they can make the drain plug location.

If you have to empty the pump oil by draining, you may find it handy to make various adapters to channel the drain oil off the pump platform. Especially useful for this are the “flat” (not round) plastic motor oil bottles. Save a few used ones and cut them apart in various different ways to make troughs to channel the oil. If necessary, you can attach a piece of large diameter plastic tubing to the spout to make a specialized funnel.

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If you do periodic oil changes on the same machine, you may want to consider installing an extension pipe on the pump drain outlet. Petcocks are also available for this. Keep in mind that the longer the drain extension, the more slowly the oil will come out.

Suction Gun

On many pumps it is possible to extend a tube through the oil fill opening clear down to the floor of the crankcase. The best tubing to use is usually 1/4-in. I.D. clear plastic (not heavy-wall). With some adaptation, you can attach this tubing to a suction gun.

The suction gun can be obtained at an automotive supply store. Now you don’t have to fuss with draining the oil. The only nuisances are having to empty the suction gun into something else and having to use a fair amount of muscle to operate the gun.

Hand Suction Pump

This is probably the most convenient device to use, especially out in the field. It combines a hand air pump with a container to hold the used oil. The air pump works “in reverse” to pump air out of the container and create a vacuum. As with the suction gun, a piece of tubing extends from the container into the pump crankcase. A shutoff valve in the tubing line allows you to pump up the vacuum.

The advantages of this method are that the air pump is easy to stroke and the used oil goes directly into a container. The shop I worked at used two versions of this device and both worked well. One version is sold commercially and comes ready to use. It is made by Big Boy Products, Inc., Warsaw, IN, and it’s called the Topside Oil Changer. Another such product is the LiquiVac, sold at big-box stores such as Lowes.

We made the other version ourselves from a plastic tank garden sprayer. In order to convert the “sprayer” into a “sucker,” you have to open up its air pump and do two things: reverse the cup washer on the plunger and reverse the flapper valve at the bottom of the cylinder.

With the cup washer and flapper reversed, it will suck when pumped, but in order for it to work well with a viscous liquid like pump oil, you must also replace the internal dip tube and the external wand/tubing with larger diameter tubing and a shutoff valve. Clear tubing is nice, because it allows you to see the oil as it is drawn out of the pump.

Electric Suction Pump

If you want the ultimate in luxury for doing in-shop oil changes, the preceding can be carried a step further by using an electric vacuum pump to produce the vacuum. That can be done almost for free if you can obtain a small working compressor from an old dehumidifier, air conditioner, or refrigerator, and a gallon jar with a metal lid.

Solder two tubing connections into the jar lid. Run one piece of tubing from the compressor inlet to the jar lid, and run another from the jar lid into the pump to be drained. Be sure that the lid seals well when screwed onto the jar. (You may have to make a gasket.)

When you turn on the compressor, the oil will be drawn into the jar with no effort on your part. Of course, you have to “repackage” the salvaged compressor. Mounting the compressor and jar on a small cart makes the apparatus easy to use around the shop.

The drawbacks of this device are that it is a nuisance to carry around if you take it out into the field, and it requires electric power.

Finishing Touches

Have your flashlight, mirror, and funnels handy to make refilling the pump as easy as possible.