Common Dump Trailer Telescopic Cylinder Problems: Dump Truck Hydraulics Troubleshooting
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Common Dump Trailer Telescopic Cylinder Problems: Dump Truck Hydraulics Troubleshooting


In a dump truck design, telescopic hydraulic cylinders include a series of steel tubes, referred to as stages, nested inside one another. Typically, a standard telescopic cylinder for a dump truck has between 2 and 5 stages. With this design, the cylinders allow for a longer extension stroke, unlike standard hydraulic cylinders, making them ideal for dump truck operations.

These truck hydraulics are moved when pressure is introduced, causing the largest tube to move, then subsequently each smaller tube. In the process of retracting the cylinder, the smallest tube will close first, up until the largest one. While this is a highly relied-upon system, it does require maintenance to ensure a well-running machine.

There are a number of issues that can arise with a hydraulic truck bed. With so many different elements to the design, troubleshooting dump truck hydraulics takes special expertise to find and solve the issue. To better understand potential dump truck telescopic cylinder issues, our telescopic cylinder repair team is breaking down the most common problems you will run into.

Dump Trailer Cylinder Vibrates And Chatters

Wondering how to troubleshoot dump truck bed hydraulics in a truck that is vibrating? There are many scenarios to look into if the cylinder seems to chatter or vibrate, including:

  1. The first thing to look at is the cylinder alignments. Excessive friction caused by misalignment can result in cylinder chatter. Make sure the cylinder is mounted and aligned correctly to rule this out.
  2. Look for air in the system. Many cylinders have an internal auto-bleed design, so follow the start-up procedure to bleed the cylinder of air. Keep your eye on any places where air may be introduced into the system and seal off any leaks.
  3. Look at the fluid level in the reservoir to ensure the system has enough to extend the cylinder completely. Add fluid as needed.
  4. Ensure the reservoir air breather isn’t blocked. In the case it is dirty, clean it or replace it for a better-running system.
  5. Check that the pump is moving oil, not worn, and properly functioning. Specifically, the gears within the pump can wear with continued use, creating more room around them where oil can pool as opposed to being forced out of the pump. A flow meter can be installed to keep an eye on the oil flow.
  6. Look to see that unloading or relief valves are properly adjusted. These should not get too low.
  7. Look for excessive back pressure on the external drain valves. If the pressure is too high, take a look at the status of the plumbing lines, too.
  8. Ensure that all valves are working properly in the system.
  9. Ensure there is no internal damage in the cylinder. If there is, it should be properly repaired or replaced.

There are many hydraulic cylinder repair needs in the case of a vibrating cylinder. If you cannot determine the cause on your own, turn to an expert for assistance.

The Tipper Body Won’t Move

hydraulic truck bed

For a tipper that won’t move, this may be a sign that the hydraulic fluid is low. However, there are a few other scenarios, such as a heavy load, a faulty pump, a faulty electric motor, or a dead battery that can cause the tipper to get stuck.

For this issue, you can:

  • Add hydraulic fluid. Start by checking that the level of fluid is where it needs to be, and ensure there are no leaks in the connections or hoses. If there is no clear issue, check that the tank has oil at least halfway up the hydraulic tank level indicator.
  • Bleed air from the system. Trapped air is known to cause issues in a dump truck hydraulics system. To bleed the air, open the valves until you don’t see air bubbles in the fluid.
  • Clean the pump suction strainer. It’s possible that a truck with a suction strainer can become clogged, making it operate less efficiently. To fix this, clean it both internally and externally to ensure a free flow of oil.

Tipper Body Lifts Way Too Slowly

If your dump truck bed raises slowly, you may have an issue with a weak battery, as well as loose battery cables or wires and other mechanical issues. In addition, this issue can be a sign of the tipper being overloaded.

Typically, the battery is the most common cause for this slow-lifting tipper. All that needs to be done to fix this is to charge the battery. If it won’t charge, that’s a sign that it’s dying. Do not continue trying to tip the truck on this kind of weak battery, however. This will cause a fuse to blow, leading to more costly damage. Instead, if your battery won't charge, try:

  • Checking whether the inline fuse is working.
  • Look at or test the battery’s electrical connections.
  • Inspect the condition of the battery.

For an engine-powered system, this issue points to a pump problem. The issue could be linked to:

  • Worn or damaged pumps as a result of internal leakage. Check the pump pressure to see if this is the cause.
  • Pump inlet cavitation as a result of a partially blocked inlet filter or damaged inlet hose. If it is cavitation, there will be a screaming sound coming from the pump, and it will also get hot quickly.
  • Relief valve pressure setting that’s not suited for the load. Check to see that the relief valve is blowing off, and look at what the pressure setting is compared to the manufacturer’s guidelines.
  • Air is drawn into the pump, causing it to not be fully pressurized. Look to see that there are no spots on the inlet side of the pump that is allowing air to be drawn in. Additionally, this can be caused if a truck is operating on a hill, causing the tank outlet to only partially flood with oil.

Hydraulic Fluid Leakage

Hydraulic fluid for dump trucks should not be leaking, and if it does, it can become a significant issue. To look for leaks, operate the hydraulic system and look at all the hoses and pipes, valves, cylinder, and pump connections for signs of a leak. If you don’t see anything, look for other signs of damage on the surface of the hoses to see if the wire reinforcement has rusted. This rusting can be caused by a damaged hose cover, which causes oil to leak from the hose. This is common in situations where a hose was exposed to road salt spray.

Additionally, hydraulic leaks can be caused by other damaged components. If the pump isn’t running or the tipper isn’t operating as it should, a professional repair service may be required to further inspect the issue.

The Tipper Is Stuck in Up Position

For a hydraulic dump bed stuck in up position, there are a few elements to troubleshoot in the system.

First, if your tipper is controlled by a solenoid valve, check to see if you can hear the valve click when it is switched to operate. If your system has an override button in the middle of the valve, press this to see if it will help the dipper descend. If this happens, this points to a burnt-out coil. You can further test this by seeing if it attracts a steel screwdriver since an energized coil is magnetic. If the coil becomes magnetic, then this is actually a sign of an issue with the valve, and won’t require a coil replacement.

On the other hand, if your machine is controlled by a manual or solenoid valve, the manual spool valve is likely stuck due to a broken linkage between the valve spool and the operating handle. That being said, there can also be other valves in the circuit in addition to the directional control that is broken or damaged. Pay special attention to any check valves and one-way restrictors, and see if any quick-release couplings are worn out. These couplings can get partially disconnected, causing issues with oil flow.

The Cylinder Doesn’t Come Down Completely

truck hydraulics

Another sign that hydraulic cylinder maintenance is needed is if the telescopic cylinder won’t come down completely. If you run into this, the first thing to look at is if there is anything mechanically holding the dump body up. Remove any obstructions under the body, following all safety guidelines, to ensure anything in the way of it coming down is removed.

Another cause of this dump truck hydraulic issue is if mechanical frictional force is getting in the way of it coming down. To solve this, look at the cylinder stage sleeve for straightness. A bent tube will cause this additional friction between the moving elements, and if it is not bent, it must be replaced.

If those aren’t the issues, look at what the pressure rate the system is running at. The pressure may have been too high, causing the cylinder to swell. When retracting, the swelled area will be forced to the larger stage, preventing it from fully retracting. Look at the sleeves for swelled arrears, and if you see any, replace the cylinder.

In addition to these issues, look at the reservoir air breather to ensure it’s not blocked. Additionally, check that the hydraulic components are working as they should and the cylinders with internal auto-bleed designs don’t have internal damage.

Mis-Staging Telescopic Cylinder

If you suspect a mis-staging issue with your truck hydraulics, take a look at:

  1. If all the air has been removed from the cylinder. A cylinder with an internal auto-bleed design should remove all air out automatically. If you notice signs of air in a manual air bleed valve, follow the air bleed procedure to remove it.
  2. If mechanical frictional force is involved. Look at the cylinder stage sleeve for straightness, since a bent tube will cause additional friction. If it’s bent, replace the cylinder.
  3. Look at the pressure rating and ensure that it’s not too high. Two stages can get stuck together if it has gotten too high, causing it to not fully extend. Look at the sleeves for signs of this, and if found, replace the cylinder.
  4. If the machine has operated over the recommended engine rotations per minute, mis-staging can be a result. This will cause damage to the cylinder, as well as the PTO and pump.


Whether you're dealing with a hydraulic dump bed stuck in up position or a dump truck bed raises slow, there are several ways you can troubleshoot the situation to find the cause. While, in some cases, there can be some simple causes and solutions, the experts can ensure your dump truck hydraulic system gets back to fighting condition.

To avoid any further issues with your dump truck and ensure quality hydraulic cylinder maintenance, our telescopic cylinder repair company is here to help. For our expert insight, contact us online today to request our services.

Cylinders inc. team



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