Diagnosing Hydraulic Surging on the Snorkel TB60

Hydraulic surging on boom lifts such as the Snorkel TB60 is a common but often misunderstood problem. When a machine begins to surge in high‑speed drive—especially after being run low on hydraulic oil—the issue can stem from aerated fluid, clogged filters, weak charge pressure, or internal pump wear. This article provides a detailed, natural‑reading explanation of how the TB60’s hydraulic system works, why surging occurs, and how experienced technicians diagnose and resolve these issues. It also includes terminology notes, real‑world stories, and broader industry context to help operators understand the hidden vulnerabilities of older boom lifts.

Understanding the Snorkel TB60 Hydraulic System

The Snorkel TB60 uses a hydrostatic drive system powered by a hydraulic pump that supplies flow to the drive motors. When the machine is placed in high‑speed travel mode, the demand on the hydraulic system increases significantly. Any weakness—such as low oil level, clogged filters, or pump cavitation—becomes more noticeable.

Key components include:

• A hydraulic reservoir
• Suction and return filters
• A variable‑displacement hydraulic pump
• Drive motors for forward and reverse
• A high‑speed/low‑speed selector valve
• A pressure gauge mounted on the filter housing (non‑functional in the reported case)

When the machine surges, it typically means the pump is struggling to maintain consistent flow.

Terminology Notes

• Surging: A rhythmic loss and recovery of hydraulic power, causing jerky movement.
• Cavitation: Formation of air bubbles in hydraulic oil due to low supply pressure.
• Charge Pressure: The minimum pressure required to feed the hydrostatic pump.
• High‑Speed Mode: A travel mode that increases flow to the drive motors but reduces torque.
• Hydrostatic Drive: A system where hydraulic pressure directly powers the drive motors.

The Initial Symptom: Surging in High‑Speed Forward and Reverse

The operator reported that the TB60 surged only in high‑speed mode, both forward and reverse. In low‑speed mode, the machine behaved normally.

This is an important diagnostic clue.

High‑speed mode requires:

• Higher flow
• Higher suction demand
• More stable charge pressure

If the system cannot supply enough oil, the pump momentarily starves, causing surging.

Why Running Low on Hydraulic Fluid Causes Surging

The machine had been run low on hydraulic oil before the issue appeared. Low oil level introduces air into the system, which leads to:

• Aerated oil
• Foaming
• Loss of pump efficiency
• Erratic pressure
• Overheating

Even after refilling the reservoir, air pockets can remain trapped in:

• Suction lines
• Pump housing
• Control valves
• Drive motors

These pockets cause intermittent loss of pressure, especially under high‑flow demand.

A Real‑World Story: The Lift That Surged for Days After a Low‑Oil Event

A technician once described a boom lift that surged violently after a worker ran it nearly dry. Even after topping off the oil, the machine continued to surge for two days. The cause was air trapped in the suction line, which only cleared after repeated cycling of the boom and drive functions. This illustrates how sensitive hydrostatic systems are to air contamination.

The Role of Filters and the Non‑Working Pressure Gauge

The operator checked the filters, but the pressure gauge on the filter housing was not working. This is significant because:

• A clogged suction filter can starve the pump
• A clogged return filter can cause backpressure
• A non‑working gauge prevents proper diagnosis

On older Snorkel machines, these gauges often fail due to:

• Vibration
• Moisture
• Internal corrosion
• Damaged bourdon tubes

Replacing the gauge is essential for accurate troubleshooting.

Common Causes of Surging in High‑Speed Mode

Experienced mechanics typically check the following:

• Low charge pressure

  • Caused by worn charge pump or clogged suction screen

• Aerated hydraulic oil

  • Caused by low oil level or suction leaks

• Clogged filters

  • Even if replaced recently, debris can accumulate quickly

• Weak high‑speed solenoid

  • Fails to fully shift the valve, causing partial flow

• Worn hydraulic pump

  • Especially common on older TB60 units

• Suction hose collapse

  • Old hoses soften and collapse under high demand

Any of these can cause surging when switching to high‑speed travel.

A Case Study: The TB60 That Surged Only When Hot

A rental company once had a TB60 that surged only after 20 minutes of operation. The cause was a suction hose that softened as it warmed, collapsing internally and starving the pump. Replacing the hose solved the issue immediately. This example shows that temperature‑dependent failures are common in aging hydraulic systems.

Why High‑Speed Mode Reveals Weaknesses

High‑speed mode increases pump displacement, which increases:

• Suction demand
• Flow rate
• Sensitivity to air leaks
• Sensitivity to clogged filters

If the pump cannot get enough oil, it cavitates. Cavitation causes:

• Surging
• Whining noises
• Heat buildup
• Long‑term pump damage

This is why surging often appears only in high‑speed mode.

Recommended Diagnostic Steps

Technicians typically follow this sequence:

• Replace or clean suction and return filters
• Inspect suction hoses for cracks or collapse
• Check for air leaks at fittings
• Replace the non‑working pressure gauge
• Measure charge pressure at the pump
• Bleed air from the system by cycling all functions
• Inspect the high‑speed solenoid and valve spool
• Test pump output under load

These steps usually identify the root cause.

Conclusion

Hydraulic surging on the Snorkel TB60—especially after running low on oil—is almost always caused by air in the system, clogged filters, suction leaks, or weak charge pressure. High‑speed mode amplifies these weaknesses, making the machine surge in both forward and reverse. Replacing the faulty pressure gauge, checking suction lines, and verifying charge pressure are essential steps in diagnosing the issue. Real‑world cases show that even minor air leaks or hose deterioration can disable a boom lift, but with systematic troubleshooting, the TB60 can be restored to smooth operation.