An excavator's hydraulic system is its heart. It powers every dig, lift, and swing. A healthy system ensures your equipment performs well. A failing one can lead to costly downtime. As a buyer, your inspection is crucial. It helps you avoid a bad purchase. Understanding key hydraulic system checkpoints protects your investment. This knowledge empowers you to choose a reliable used excavator.
Did You Know? Major hydraulic systems failures can be expensive. Reactive maintenance might cost between $45,000 and $85,000. Even a single failed hydraulic pump can set you back $2,000 to $3,500 for parts and labor. A smart inspection can save you thousands.
You must check all hydraulic parts. Look at hoses, cylinders, and fluid. Listen for strange noises from the pump. Test the boom, stick, and bucket functions. Make sure they move smoothly and powerfully. Check for cylinder drift by holding a load in the air. Finally, review the machine's service history. These steps help you assess the excavator's true condition.
The Initial Walk-Around: Key Visual Inspections
Your first look at a used excavator tells you a lot. This initial walk-around is a critical part of your equipment inspections. You will focus on the physical condition of the hydraulic system. Pay close attention to the hoses, fittings, and cylinders. These key inspection points can reveal hidden problems before you even start the engine. A careful visual inspection helps you understand the machine's true condition.
Examining Hydraulic Hoses and Lines
Start by looking at all the hydraulic hoses. They are the veins of the equipment, carrying fluid under high pressure. Age and use can wear them out. You should look for clear signs of degradation.
What to Look For:
Cracks and Abrasions: Check the outer cover for cracks or areas where it has been rubbed raw.
Bulges or Blisters: A bulge means the inner layers of the hose are failing. This hose could burst at any time.
Brittleness: Touch the hoses. They should be flexible, not hard or stiff. A brittle hose can easily crack.
Kinks or Crushed Sections: Any damage that restricts fluid flow is a major problem.
Hoses are a common replacement item. Seeing one or two new hoses is normal. Seeing many old, cracked, and bulging hoses is a red flag. It suggests poor maintenance.
Spotting Leaks at Connection Points and Seals
Leaks are the most common hydraulic issue. They are also the easiest to spot. A small drip can lead to big problems. It lets fluid out and allows dirt and air to enter the system. You must check every connection point. Look where hoses meet cylinders, pumps, and valves.
Common Leak Spots Check around cylinder seals, motor seals, and hose fittings. Look for wet spots, clean areas where oil has washed away dirt, or drips of fluid on the ground. A noisy pump can also signal a problem, often caused by air getting into the system through a leak.
Do not ignore small leaks. They show that seals are wearing out. Over time, they will only get worse. This can reduce system pressure and damage internal components.
Inspecting Hydraulic Cylinders for Damage
The large cylinders power the boom, stick, and bucket. Their condition is vital for the excavator's performance. You need to examine the shiny chrome rods on each cylinder.
Extend the cylinders if possible. Run your hand carefully along the rod. It should feel perfectly smooth. Any pitting, scoring, or scratches can destroy the cylinder's seals. Damaged rods allow fluid to leak out. They also let contaminants in. This damage leads to poor performance and can cause the cylinder to fail without warning. Even a tiny increase in surface roughness can reduce seal life by 30%.
The Cost of Cylinder Damage A simple cylinder reseal might cost you around $150 if you only need a seal kit and labor. However, if the rod is scored or bent, the cost rises quickly. A new rod and machining work can push the repair bill much higher. A thorough check here saves you from future expenses.
Checking the Hydraulic Fluid Tank and Level
The hydraulic fluid is the lifeblood of your excavator. It transfers power, lubricates parts, and cools the system. The condition of this fluid tells you a lot about the health of the entire system. This part of your inspection is simple but reveals critical information.
First, locate the hydraulic tank. You will find a sight glass on its side. The excavator should be on level ground with the boom, stick, and bucket positioned correctly. Check the manufacturer's guide for the proper equipment posture. The fluid level should be between the "high" and "low" marks on the glass. A low level might indicate a leak. An overfilled tank can cause the fluid to foam and overheat.
Next, examine the fluid itself. Healthy fluid is clear and amber-colored, like new oil. Look closely for any signs of trouble. Contamination is a major enemy of any hydraulic system. It is responsible for up to 85% of premature component failures and can reduce system efficiency by 25-40%.
Quick Tip: What Does the Fluid Tell You?
Milky or Cloudy: This is a clear sign of water contamination. Water causes rust, reduces lubrication, and damages pumps.
Foamy or Bubbly: This indicates air is in the system. Air can enter through leaks or a low fluid level, causing spongy and erratic operation.
Dark Color or Burnt Smell: This means the fluid is old or has been severely overheated. It has lost its ability to protect the equipment.
Contamination is the source of 32% of all hydraulic failures. You must understand its primary causes.
Water: Water can enter the system from condensation, pressure washing near seals, or improper fluid storage.
Air: Air bubbles can get in through loose connections, damaged seals, or a low fluid level.
partículas Dirt and Particles: Tiny particles of dirt, dust, and metal act like sandpaper inside your system. They enter through worn seals, breather caps, or during careless maintenance.
Finally, look at the tank itself. Check for dents, rust, or damage. A well-maintained machine will have a clean tank area. This simple check gives you a clear picture of the fluid's condition and the overall maintenance quality of the excavator.
Powering Up the Excavator: Operational Tests
Your visual inspection gave you a good baseline. Now, you will start the engine to test the excavator's performance under power. This operational phase reveals how the hydraulic system truly behaves. You will listen for noises, test functions, and feel for responsiveness. This is where you confirm the health of the machine's core components.
The Cold Start-Up Procedure
How an excavator starts from cold tells you a lot. A proper warm-up is essential, especially in cooler climates. It protects the system from damage caused by thick, cold fluid. You should follow a careful procedure to prevent stress on the components. This simple test shows if the equipment has been treated with care.
Pro Tip: The Warm-Up Matters Starting an engine and immediately working it hard is a major mistake. Cold hydraulic fluid is too thick to lubricate parts correctly. This can cause pump cavitation and premature wear. A patient warm-up protects your potential investment.
Follow these steps for a safe and revealing cold start:
Check the Fluid Again: Before starting, verify the fluid is not too thick. If it is cold, the fluid should still be able to drip from a dipstick. Fluid that is too viscous can starve the pump.
Start the Engine: Start the engine at a low to medium idle. Do not rev it immediately. Let the engine and fluids warm up gradually.
Engage Functions Slowly: After a few minutes, slowly engage the boom, stick, and bucket functions for about 10-15 seconds at a time. This circulates the warming fluid through the entire system without putting it under heavy load.
Listening to the Hydraulic Pump
The hydraulic pump is the heart of the system. While the engine is running, you should listen carefully to the pump. A healthy pump makes a smooth, consistent humming sound. Loud or unusual noises are a major red flag that signals expensive problems. Two common problem sounds are cavitation and aeration.
Cavitation occurs when the pump is starved of fluid. This creates vapor bubbles that collapse under pressure, damaging internal parts.
Aeration happens when air gets into the system, often through a leak. Air compresses, causing spongy operation and loud noises.
You can use this table to help identify these sounds:
Problem | Sound Description | Likely Cause |
|---|---|---|
Cavitation | A steady, high-pitched whining or rhythmic knocking | Clogged suction filter, thick fluid, or a blocked line |
Aeration | An erratic rattling, like marbles or gravel in the pump | A leak on the suction side of the pump or low fluid level |
Ignoring these noises is a costly mistake. A main pump replacement on a mid-size excavator can range from $1,500 to over $8,000 for the part alone, with labor adding another $500 to $3,000.
Testing Boom, Stick, and Bucket Functions
Now you will test the machine's primary functions. You need to feel how the equipment responds to your commands. The movements should be smooth, precise, and powerful. Jerky or slow operation points to serious issues.
Go through a full range of motions. Lift the boom all the way up and down. Extend the stick all the way out and bring it back in. Curl and uncurl the bucket completely. Do this several times. Pay attention to the speed and consistency of each movement.
Is it the Pump or a Valve? If you notice weak or slow performance, the problem could be a weak pump or a faulty relief valve. You can perform a simple test. If pressure seems low across all functions, the pump may be worn. However, if you notice pressure fluctuating wildly or a single function is weak, a specific relief valve might be stuck or failing. A faulty relief valve often cannot be adjusted and will cause inconsistent pressure readings.
This part of your inspection is crucial. It directly tests the components that do all the work. Any weakness here will directly impact your productivity on the job site.
Evaluating the Swing Motor and Bearing
The swing system allows the excavator's house to rotate. A faulty swing motor or bearing can cripple your equipment's productivity and pose a safety risk. Your inspection of this system is vital.
First, position the excavator on level ground. Swing the house 90 degrees to one side and stop abruptly. You should observe a smooth, quick stop. A common symptom of a problem is a back-and-forth rocking motion after the swing stops. This indicates wear in the turntable bearing or an issue with the swing brake.
Next, perform a full 360-degree rotation in both directions. Listen for any unusual noises and feel for vibrations.
Warning Signs of Swing System Failure You must watch for several key indicators of wear or damage. Ignoring these can lead to major repairs.
Excessive Play: Any noticeable free movement or "slop" during operation.
Unusual Noises: Grinding, popping, or clicking sounds point to bearing or gear problems.
Visual Damage: Look for cracks, deformations, or loose and missing bolts around the swing bearing.
A worn swing system leads to reduced precision and control. This makes delicate work nearly impossible and increases wear on other components of the equipment.
Checking the Travel Motors
The travel motors drive the tracks. They must be powerful and reliable to move the excavator around a job site. Weak or failing travel motors can leave your machine stranded.
To test them, drive the excavator forward and backward in a straight line for at least 50 feet. The machine should travel straight. If it pulls to one side, one motor may be weaker than the other. You should also test the motors' power by driving up a small, stable incline.
Listen closely to the motors during these tests. Healthy motors operate quietly. Loud noises are a clear sign of trouble.
Symptoms of a Failing Travel Motor:
Slow Travel Speed: You will see a clear reduction in the machine's travel speed.
Loud Noises: Whining, screeching, or grinding sounds can indicate fluid flow issues or internal component failure.
Overheating: The motor housing becomes extremely hot during normal operation.
Visible Leaks: You can see hydraulic fluid leaking from the motor seals.
Lack of Power: One or both tracks may seem weak, or a motor may not move at all.
Another issue to watch for is brake drag. This happens when the internal brake does not fully disengage. It creates constant resistance and causes poor drive performance.
Critical Hydraulic System Checkpoints Under Load
You have tested the excavator's basic functions. Now you will push the equipment to its limits. These critical hydraulic system checkpoints reveal how the machine performs under real working pressure. This phase of your inspection helps you find problems that only appear when the system is working hard.
Performing a Stall Test
A stall test measures the maximum pressure the system can build. It is a direct test of the main relief valve and the pump's health. You should perform this test carefully for each main function.
To do this, you fully extend or retract a cylinder until it stops. For example, you can curl the bucket all the way in. Then, you continue to hold the control lever for a few seconds. You should hear the engine load up and the relief valve activate with a distinct sound. This shows the system is reaching its peak pressure. If the engine does not labor or you hear no relief sound, the pump or valve may be weak.
Checking for Cylinder Drift
Cylinder drift is when a raised boom or stick slowly lowers on its own. This indicates internal leaks in the cylinder seals or control valve. A bad drift problem makes the excavator unsafe and difficult to operate.
To check for drift, lift a heavy load, like a bucket full of dirt. Raise the boom so the bucket is several feet off the ground. Shut off the engine and let the equipment sit for at least five minutes. Watch the cylinders closely. A healthy hydraulic system will show very little movement.
Industry Standards for Drift According to industry test standards (SAE J1336), a cylinder holding a load for 5 minutes should have:
Less than 3 mm (⅛ in.) of rod movement.
No more than 10 cm³ (about 0.6 in³) of internal fluid leakage.
Measuring Cycle Times
Cycle times measure how fast the excavator can perform a complete movement. Slow cycle times mean lost productivity and often point to a worn pump or other system issues.
You can measure the time it takes to complete a full function. For example, time how long it takes to raise the boom from the ground to its highest point. You can also time a full dig cycle. Compare your results to the manufacturer's specifications for that excavator model. Slow times are a major red flag. These final hydraulic system checkpoints give you a complete picture of the machine's health.
Advanced Equipment Inspections for Used Machinery
You have completed the visual and operational tests. Now, you can perform advanced equipment inspections for a deeper look at the used machinery. These final hydraulic system checkpoints provide critical data. They help you make a confident purchase. This detailed inspection separates a well-maintained excavator from a potential problem.
Analyzing a Hydraulic Fluid Sample
Taking a hydraulic fluid sample gives you a scientific look inside the system. You can send this sample to a lab for analysis. This is a key part of comprehensive equipment inspections. The report reveals hidden issues that your eyes cannot see. A professional analysis tests for many contaminants.
What a Fluid Analysis Uncovers:
Particulate Contamination: The test finds tiny particles of metal, dirt, and dust. Even microscopic hard particles cause heavy wear on internal parts.
Sludge and Varnish: These sticky substances are signs of old, oxidized fluid. They can make important valves stick.
Water: Water is a major enemy. It causes rust and damages components.
This analysis provides a clear picture of the equipment's internal health. It is a small investment that can prevent a major failure after your purchase.
Checking the Hydraulic Filters
The hydraulic filters protect the system from contamination. You should check the main filter housing. Look for a date or the number of operating hours written on the filter. This shows you when it was last changed. A recent change is a good sign. If the filter is old or the date is missing, it suggests poor maintenance. An owner who tracks filter changes based on operating hours likely takes good care of the machinery. This simple check during your equipment inspections offers valuable insight.
Reviewing Service and Maintenance Records
Service records tell the story of the excavator. You should ask the seller for all maintenance logs. Good records show a history of care and attention. They prove that the owner prioritized preventive maintenance based on operating hours. A well-documented machinery history includes oil changes, filter replacements, and repairs. This information is vital for any piece of heavy equipment.
All inspection and service activity should be recorded in one place. Each piece of equipment needs its own record. This log helps owners stay accountable for preventive maintenance. It also builds the habit of prioritizing these important tasks.
Look for regular services at the recommended operating hours. A logbook with consistent entries for every 250, 500, and 1000 operating hours is a great sign. Missing records or inconsistent entries are a red flag.
Red Flags: Warning Signs of a Failing Hydraulic System
You must learn to spot the warning signs of a failing system. These red flags tell you when to walk away from a potential purchase. Ignoring them can lead to expensive repairs and significant downtime. A careful inspection of these key areas will protect your investment.
Milky, Foamy, or Burnt Hydraulic Fluid
The fluid’s appearance reveals the internal condition of the system. You should always check it closely. Healthy fluid is clear, but contaminated fluid is a major problem.
A milky look in the fluid is a strong sign of water contamination. Water causes rust, reduces lubrication, and can lead to expensive pump cavitation. Foamy fluid tells you that air has entered the system. Air contamination reduces the equipment's efficiency and can cause jerky, inconsistent performance.
Both water and air contamination will:
Cause sluggish or inconsistent performance.
Accelerate wear on seals and moving parts.
Excessive System Heat
An excavator hydraulic system generates heat during operation. However, too much heat is a destructive force. It breaks down the fluid and damages critical components like seals and hoses.
You should check the system temperature after running the machine. While specific ranges vary, you should be cautious if the system feels excessively hot. Temperatures reaching around 140°F (60°C) are a concern. Significant damage can begin to occur once temperatures climb over 180°F (82°C). Overheating is a clear sign that the system is struggling, possibly due to a worn pump, a stuck valve, or a blocked cooler.
Slow or Jerky Hydraulic Movements
The machine’s movements should be smooth and responsive. Slow or jerky operation is a serious red flag that points to underlying problems. These issues make the machine inefficient and unsafe to operate.
Air bubbles in the system are a common cause of jerky movements. You will notice inconsistent or shaky performance. Other potential causes include:
A malfunctioning control valve that cannot regulate pressure.
Dirty fluid that clogs the system and causes inefficient operation.
Damaged cylinders that lead to irregular movement.
Loud or Unusual Noises
You should listen carefully when you test an excavator. The sounds it makes can tell you about its internal condition. A healthy hydraulic system operates with a consistent, low hum. Loud or strange noises are serious red flags. These sounds often signal that internal components are failing or that the system is under stress. Ignoring them can lead to a catastrophic failure of the equipment.
Pro Tip Never dismiss a new noise. A sound that was not there yesterday could be the first sign of a major problem. Early detection saves you from expensive repairs.
Different noises point to specific problems within the hydraulic system. You can use this guide to help identify the potential cause of a sound you hear.
Noise Type | Likely Cause |
|---|---|
Cavitation: The pump is starved for fluid, causing bubbles to form and collapse violently. This can be from a blocked filter or thick fluid. | |
Aeration: Air is leaking into the system. This is often caused by a bad seal or a loose connection on the suction side of the pump. | |
Mechanical Wear: Internal parts are grinding against each other. This points to severe contamination or a lack of lubrication. | |
Misalignment: The pump or motor couplings may be misaligned, causing stress and wear on bearings and other mechanical parts. |
These noises are direct warnings of damage happening inside the hydraulic system. A whining sound from cavitation can destroy a pump quickly. A grinding noise means metal particles are likely circulating through the entire system. You must investigate any unusual sound immediately.
As a buyer, your best defense is a thorough inspection. This guide's hydraulic system checkpoints help you evaluate used machines. You can confidently assess any excavator and avoid a bad purchase. A professional review during equipment inspections can save you from costly repairs on your new excavator.
Final Takeaway A smart buyer protects their purchase of this essential machinery. Remember, the health of hydraulic systems is vital for any heavy equipment. Do not compromise on the health of your excavator equipment.
FAQ
What is the first thing to check on a used mini excavator?
You should always check the hydraulic fluid first. Look for a milky or burnt appearance. This simple check on a mini excavator reveals a lot about its maintenance history. The mini excavator market has many options, so a good first check is vital.
Are small hydraulic leaks a big deal on a mini excavator?
Yes, you should treat even small leaks seriously. A small leak on a mini excavator lets dirt and air into the system. This can cause major damage over time. The mini excavator market is competitive, so you can find a machine without leaks.
How do I find the best mini excavator for my needs?
You find the best mini excavator by matching its size and power to your jobs. Research each mini excavator brand. A thorough inspection of the mini excavator's hydraulic system is also essential. The global mini excavator market offers many choices for your specific work.
Why is a mini excavator a good choice?
A mini excavator is versatile and can work in tight spaces. This makes the mini excavator very popular. The mini excavator is also easier to transport than larger machines. A quality mini excavator holds its value well.
