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How to Change the Engine Oil and Filter on a CAT 314E Mini Excavator
Written by Luis Montes Updated on May 16, 2025
We’ll cover how to service the engine of a CAT 314E mini excavator. Although focused on a particular make and model, we’ll discuss similarities with other brands, so the articles can also help guide you in servicing other equipment.
On the Tekamo HD YouTube channel, you can watch Keith, an expert technician, perform the service.
Drain the Engine Oil
Like the CAT 314E, you must remove a belly pan to reach the drain plug on midsize to large excavators. You can reach the drain plug without removing any pans on most compact models, such as the John Deere 17G, Kubota KX71-3, or Hitachi ZX40UR-2, among others.
The number of bolts holding the belly pan also varies among makes and models. The CAT 314E belly pan has four bolts.
Before removing the bolts, inspect their holes. Like the CAT 314E, machines from John Deere, Hitachi, and Volvo feature slotted holes (located further in, toward the cab), making your job much easier.
Just loosen the bolts from the slotted holes and remove the others. Then, you can slide the belly pan out to remove it and follow the same steps for installation, instead of holding the pan while trying to put the bolts back in.
Next, grab an empty bucket or pan to catch the oil. Depending on the make and model, you may need more than one drain pan.
Another thing to consider is the type of drain. The CAT 314E has a needle valve with an attached hose piece. Other machines, like the Komatsu PC200LC, have a ball valve or a simple plug, as in the case of the John Deere 85G. Be careful when removing the drain plug. As soon as it comes out, oil will pour out.
Wait for the oil to drain completely, then close the valve and reattach the belly pan.
(Note: Looking closely at the pictures, you will see Keith wearing gloves. Other mechanics prefer PR88 cream for dexterity or if working in tight areas where sharp edges can tear rubber gloves.
Change the Oil Filter
Because some machines will require more than one drain pan, we suggest not draining the engine oil and changing the filter at the same time. Finish with the engine oil and then work on the filter.
The engine oil filter is in the right-side compartment.
The filter’s canister has a hex-shaped piece to use a wrench or a ratchet. Using the tool of your preference, turn the canister clockwise to loosen it.
Place a catch pan under the filter and finish removing it by hand. The filter’s housing will continue to drip oil, so leave the catch pan there.
Keith, the expert HD mechanic who serviced the machine, shared a helpful tip from his over 25 years of experience.
Whenever he does fluid filters, he brings an extra bucket and a piece of metal screen that he places on top of the bucket. Then the filters go upside down on that piece of metal to drain safely into the bucket, so you don’t have to throw away filters full of oil anywhere.
Sometimes, you’ll buy the inner filter (made of cellulose fiber) and reuse the canister. In this case, we got a factory OEM filter that included the canister, so we replaced the whole filter.
Lube the filter’s rubber gasket so it doesn’t bind and rip as you screw tight the filter. You can use oil from the top part of the filter’s housing.
Install the filter hand-tight. Although we usually recommend not using tools to tighten spin-on filters, we used a wrench to give ours a slight snug until the filter stopped. Don’t go any further. Otherwise, you’ll strip the threads and be forced to replace the whole housing.
What about pre-filling the filter? We didn’t. The decision to prime engine oil filters varies among mechanics and several operator manuals, even from the same manufacturer. Our article “1,000 Hour Service Interval Guide for a Komatsu PC200LC Excavator – Part 1” further discusses the topic.
Refill the Engine Oil
Now, open the machine’s top hood, remove the fill cap, and set your funnel in place.
If you’re using an oil bucket (we used a 5-gallon bucket of 15W40 Tekamo Oil), open the bucket’s vent to pour the oil in a steady stream, rather than having a glugging effect and making a mess.
Also, don’t pour the oil too fast. Depending on the engine bay’s design, this could cause more than a mess. Keith told us that pouring oil too fast on machines such as the Hitachi 75 can accidentally dump oil into the intake system, causing a serious problem when starting the machine.
Check the hydraulic oil level.
To get an accurate oil level reading, park the machine on a level surface with the arm cylinder fully retracted and the bucket cylinder fully extended. Lower the bucket and blade to the ground and stop the engine. The oil level should be between the top and bottom marks on the sight gauge on the hydraulic tank.
Check the PILOT SHUT OFF 5 amp fuse (F17) and replace it if necessary.
One more thing you should do is inspect and clean the suction screen. The suction filter is within the hydraulic tank.
Hydraulic Functions Are Slow Or Have Little Or No Power
Like before, check the oil level and the suction filter.
Make sure you’re using the proper oil viscosity. A thick oil can slow response times and reduce efficiency, while thin oil won’t provide sufficient protection, resulting in increased wear.
When working in freezing weather, perform a hydraulic warm-up.
CAUTION: Prevent possible injury from unexpected machine movement. Clear the area of all persons before running your machine through the warm-up procedure. If the machine is inside a building, warm the travel circuit first and move the machine to a clear area outside. Cold oil will cause machine functions to respond slowly.
- Run the engine at 1/2 speed for 5 minutes. Don’t run at fast or slow idle.
- Travel and swing functions slowly, initially moving only short distances.
- Operate the boom, arm, and bucket functions. First, move the cylinders a short distance in each direction.
- Continue cycling cylinders by extending until you reach the entire stroke. IMPORTANT: Holding function actuated for more than 30 seconds can cause damage from hot spots in the control valve.
- Actuate the bucket curl function (cylinder extend) for 10 seconds and release for 5 seconds. Continue this maneuver for 2-1/2 minutes.
- Repeat the procedure with the bucket dump function.
- Operate all hydraulic functions to distribute warm oil in all cylinders, motors, and lines.
- If hydraulic functions still move slowly, repeat steps 5 and 6.
Are you operating the engine too slow? Remember that the engine drives the hydraulic pump. So, the engine´s speed directly affects the speed at which the pump operates, which, in turn, affects the speed and efficiency of hydraulic functions. Try increasing the engine’s speed.
Check if you need to replace the hydraulic tank cover. A damaged cap can cause pressure loss, reducing performance and slowing operations.
As you work through the maintenance and repair of your John Deere 35G, remember that the right tracks can significantly impact your excavator’s performance and longevity. Take a look at our John Deere mini excavator tracks for a selection of tracks designed to OEM specifications.for
Hydraulic Oil Overheats
Check for clogged filters, a low oil level, and that you are using the correct oil viscosity.
Inspect the radiator and clean it if needed. Also, take a look at the fins and straighten those bent. Bent fins can disrupt airflow through the radiator, making it less effective at dissipating heat from the coolant.
Overheating can be the consequence of contaminated oil. Contact your authorized dealer to help you find the contamination source.
| WHAT DOES CONTAMINATED OIL LOOK LIKE? | |
|---|---|
| APPEARANCE | CONTAMINANT |
| Cloudy, discolored, or murky. | Dirt, dust, debris. |
| Shiny | Metal. |
| Milky. | Water or coolant. |
| Foamy or bubbly. | Air. |
Oil Foams
Several things can cause foam formation:
- High or low oil level.
- Incorrect oil type.
- Water or air in the oil.
Remember to contact your authorized dealer if the oil is contaminated.
Lastly, check for kinks or dents in the oil lines.
No Swing Function
Is the pilot shutoff lever in the unlocked (down) position?
Inspect and correct pinched or kinked pilot control valve hoses.
Swing Function is Jerky
Fill the swing bearing with grease.
Remove rocks or mud jammed in the track frame.
Slow Travel Speed Only
The pilot control valve regulates the flow of hydraulic fluid to the excavator’s travel motors or tracks, so check for pinched or kinked pilot control valve hoses.
Travel is Jerky
Try increasing the engine’s speed — because of the link between the engine and the hydraulic system.
Slow engine speeds may lead to stalling the hydraulic system, mainly when the equipment is under heavy load. Stalling can result in sudden stops and jerky movements as the hydraulic components struggle to function at reduced power levels.
Check for rocks or mud jammed in the track frame.
Also, adjust the track sag.
Engine Stops When Travel Or Control Lever Actuated
There are two possibilities:
- Replace the fuel and air filters if clogged.
- Bleed the air from the fuel system.
Angle Blade Suddenly Drift
If the angle blade moves without you operating it, there might be a problem with the system or circuit relief valves. Check and replace accordingly.
Angle Blade Doesn’t Work or Moves Slowly
To troubleshoot the lack of movement on one side of the blade, check the hose routing for leaks and inspect the center joint. Repair, add grease, or replace according to the problem.
Last Thoughts
Although this guide focused on a John Deere 35G mini excavator, several troubleshooting solutions also apply to machines of other makes and models.
Share this post with other heavy equipment owners and operators. You might be a click away from helping them figure out what’s going on with their mini excavator.