1,000 Hour Service Interval Guide for a Komatsu PC200LC Excavator – Part 3

In the last post, we changed the secondary fuel filter, filled the engine oil, and checked the level and condition of the engine coolant.

In the third part of this series, we’ll change the hydraulic and breather filters and refill the swing gearbox oil.

We also have a video version on the Tekamo HD YouTube channel. Check it out.

Before you open the hydraulic oil tank, remove the breather cap to vent it. You’ll likely hear a pop or hissing sound.

As our guide “500-hour service tasks on a John Deere 17G” explains, system overloads, clogged filters, or thermal expansion cause the tank to build up pressure. You must vent this pressure before removing the filter cap; otherwise, oil will push out.

Once you vent the oil tank, break loose the cap bolts. In the video version, Shawn uses a ratchet to do this. However, as our post on breaker bars and ratchets discusses, a breaker bar could have been a better option.

Remove the hydraulic tank cap and the spring holding the bypass valve, and wait a few minutes for the oil level to drop.

Remove the bypass and hydraulic filters. The oil will take a while to drip, so leave the filters inside a bucket or pan.

Install the new hydraulic filter. It sits around a “spigot” at the bottom of the hydraulic tank.

Since the Tekamo crew maintained this equipment on time, there was no need to change the bypass filter.

The bypass filter works when the hydraulic filter gets clogged. The bypass valve then becomes the path of least resistance for the oil, which opens due to the oil pressure.

The following animation shows the role of the bypass valve and filter.

As usual, we encourage you to change the O-ring every time you do the hydraulic filter. Shawn claims, “The O-ring is a minor cost that will save you hassles. A worn O-ring will let moisture inside the tank and degrade your oil quickly.”

Reinstall the bypass valve, its spring, and the tank cap.

When reinstalling the cap, tighten the bolts in a cross pattern (until the bolt heads sit) to make the cap go down evenly. Then, go along to make sure everything is snug. Overtightening one side will deflect the plate.

Because hydraulic oil contains 10% dissolved air by volume, a clogged hydraulic filter increases the inlet restriction, releasing the dissolved air, a phenomenon known as cavitation.

During cavitation, tiny air bubbles appear on the pressure side of the pump. The implosion of those little gaseous cavities is measured in tons/in2! The tiny implosions will chip away metal parts inside the pump.

Rory McLaren, Founder and Director of the Fluid Power Training Institute, Inc., says oil contamination will worsen cavitation exponentially. Every piece of contamination acts as an abrasive seed growth cavitation.”

Finally, replace the foam around the spring of the breather cap.

The breather cap regulates the air volume inside the hydraulic tank. Air volume inside the tank varies due to the actuators’ movement and as the machine warms up and cools. Overpressure and vacuum effects would occur inside the tank without a breather cap.

Because the breather cap draws in air, it needs a filter to trap debris and dirt from getting inside the hydraulic system.

Reinstall the plug in the swing gearbox drain line and fill the swing machinery case until you reach the top mark.

The Komatsu PC200LC requires 1.9 gallons (1.7 liters) of 30 weight oil, or SAE 30. The 30 defines the oil’s viscosity at normal engine temperatures. The lower the number, the lower the viscosity, and the faster the oil will move around the engine.

Shawn used a pail pump to fill the oil. The oil pushes air inside the swing gearbox, which comes out through the inlet pipe, producing a blurb effect. The dipstick is removed to provide air with another path out and avoid the blurb effect.

In the next post of this series, we’ll change the final drive oil and replace the engine and cabin air filters on the Komatsu PC200LC.