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Common Lorry / Truck Hydraulic Problems and Solutions

Truck unloads sand on the construction siteLorries & trucks require properly functioning hydraulics to operate normally. A hydraulic problem can cause the tipper or crane to fail. Fortunately, there are various ways of troubleshooting truck hydraulics in a number of situations. These are some common problems and solutions.

The Tipper Body Won’t Go Up or Down

If the tipper is stuck, hydraulic fluid may be low. A heavy load, faulty pump or if powered by a DC powerpack; a faulty electric motor or a dead battery may cause the problem too. To address this situation, you can:
 
  • Add hydraulic fluid. Check the fluid level and for small leaks in the hoses or connections. If no other problems are evident, with the truck parked on the flat ensure the tank has oil at least half way up the hydraulic tank level indicator with the manufacturer’s specification of hydraulic fluid.
  • Bleed air from the system. Trapped air can cause hydraulic system problems. Open the relief valves until you don’t see any air bubbles in the fluid.
  • Clean the pump suction strainer. If there is a suction strainer in the tank it may haver become clogged, in which case the pump will become less efficient. Clean it thoroughly both internally and externally to ensure a free flow of oil to the pump..

The Tipper Body Lifts Very Slowly

On DC powered systems a weak battery can affect lifting power, as can loose battery cables or wires.  It’s also possible the tipper is overloaded or there are pressure or mechanical issues.

The battery being the most likely culprit, you’ll want to try charging it. If it won’t charge, it may be dying.  Trying to tip with a weak battery can cause fuses to blow, leading to more damage.

If the battery does not charge:
 
  • Verify whether the inline fuse is working or not.
  • Inspect and/or test the battery’s electrical connections.
  • Check the overall condition of the battery.
On engine powered systems the problem is most likely due to a pump problem. As the tipper is lifting slowly we know that the pump is engaged with the truck transmission so is turning. The possible problems could be:
 
  • Worn or damaged pumps causing extra internal leakage, can be checked by testing the pump pressure.
  • Pump inlet cavitation due to a partially blocked inlet filter or damaged inlet hose.If cavitating there will tend to be a screaming sound coming from the pump and it will get hot very quickly.
  • Relief valve pressure setting borderline for the load, again check to see if the relief valve is blowing off and if so check the pressure setting is as per the machine manufacturer’s guidelines
  • Oil aeration: if for some reason air is being drawn into the pump, the system will not be fully pressurised.Check that there are no points on the inlet side of the pump that might allow air to be drawn in.Is the truck operating on a hill causing the tank outlet to be only partially flooded with oil?

Hydraulic Fluid Is Leaking

Operate the hydraulic system and check all pipes / hoses, valve, cylinder and pump connections for leaks. If nothing obvious, check for imperfections on the surface of any hoses in case the wire reinforcement has rusted due to a damaged hose cover leading oil to weep from the hose. This can be common when hoses are exposed to road salt spray.

Hydraulic leaks can also be caused by damaged components. If the pump isn’t running or the tipper isn’t operating normally, and you’ve tried the tips mentioned above, you may need a professional repair service.
 

Tipper Is Stuck in the Up Position

In this case, it’s important to know how to troubleshoot hydraulic systems. When the tipper is stuck, check the following:
 
  • If controlled by a solenoid valve: Can you hear the valve click when the switch is operated? If there is an override button in the middle of the valve, press this and if this allows the tipper to descend then it probably means that the coil is burnt out. An energised coil is magnetic so you can check it by seeing if it attracts a steel screwdriver when energised.  If the coil becomes magnetic then it would indicate a problem with the valve itself, if it doesn’t then would indicate that the coil needs to be replaced.
  • If controlled by a manual or solenoid valve: Manual spool valves do not tend to get stuck unless the linkage to the valve spool from the operating handle is broken or damaged. However there are probably other valves in the circuit in addition to the actual directional control valve and these can become blocked or damaged.   Check in particular for any check valves or one way restrictors that may be fitted. Check also to see if there are any quick release couplings in use as these can wear causing them to shut completely, equally they may have become partially disconnected, again preventing all oil flow.
White House Products Ltd. can help with any sort of Lorry / Truck hydraulic system issue.  We stock replacement parts from leading manufacturers and have an in-house repair service.  Call +44 (0) 1475 742500 to learn more.
 

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