Understanding Hydraulic Repairs

A hydraulic jack serves one fundamental goal: the lifting of heavy loads. Jacks are designed to provide force multiplication to enable a worker to amplify their strength through the jack's hydraulics or mechanics to accomplish this goal.

There are two main types of jacks commonly in use; one type uses hydraulic pressure for lifting (hydraulic jacks), while the other uses a screw thread to achieve lift (mechanical jacks). Of the two, hydraulic jacks usually provide higher lift capacity and are more reliable.

Types of Hydraulic Jacks

Hydraulic jacks are available in two varieties: floor jacks and bottle jacks. Floor jacks have a horizontal shaft that pushes on a crank. The crank connects to a lifting pad that rises vertically. These jacks are capable of lifting several tons.

Bottle jacks have been around longer, and their name derives from their resemblance to an old-fashioned milk bottle. Bottle jacks have a vertical shaft that raises a platform called a bearing pad. They can lift up to several hundred tons, depending on the specific capabilities of the model being used. However, these jacks typically cannot lift the load to the same height as with a floor jack.

Both types of jacks operate under the same basic principle: In a closed container, the pressure is the same in all directions. In the case of a hydraulic jack, this container is a cylinder, and it holds incompressible hydraulic fluid. Hydraulic fluid is forced into the cylinder through a check valve that prevents the fluid's backflow. The check valve keeps the cylinder pressurized so the load does not drop. As pressure builds in the cylinder, the force pushes upward on the plate of the jack and lifts the load resting on it. The weight of the load lowers the plate when the check valve is released, allowing the hydraulic fluid a path to exit.

Common Types of Jack Damage

There are some issues that are common to all types of hydraulic jacks which can impact their operation and safety. At some point, users will likely encounter leaks, rams that won’t lift, safety valves that get tripped, damage to the frames, and jack handles that kick back. While many hydraulic jack repairs are easy to accomplish, others might require the assistance of a professional.

Leaks, in particular, are extremely common, and result from a failed or dislodged seal or O-ring. Repair involves draining the hydraulic fluid, disassembling the jack, and inspecting the seals. Be sure to look carefully for cuts, tears, seals that are out of place, degradation, scratches, and so on. These issues are an indication that the seals or O-rings need to be replaced.

Repairing leaking seals can be a significant undertaking, especially for those not experienced in jack repair. Novices might want to leave this type of issue to a professional with the requisite experience. Also, if the leaked fluid is cloudy or foamy, that indicates the presence of water or air in the hydraulic system and could mean that the hydraulic fluid needs to be replaced and the potential source of the intrusion investigated.

Jacks may also be overloaded, causing the safety valve to trip. The purpose of this safety feature is to prevent the jack from being loaded beyond its rated operating pressure, typically measured in pounds- force per square inch (psi). A jack will not behave the same way after the safety valve has been tripped. The ideal way to address this issue will vary by manufacturer, so always consult the service manual when this occurs. Professional service is recommended in these instances to restore safe operation of the jack.

In other cases, rams may stop lifting, which is usually the result of insufficient hydraulic fluid in the reservoir. Luckily, this is a repair that even beginners can handle. When there isn’t enough hydraulic fluid present, air may become trapped inside of the system. The solution here is to add the appropriate amount of hydraulic fluid, then turn the jack to its release position. Next, pump a few times to purge out the trapped air. Then, refill the reservoir and place the seal cap back on. Be careful to avoid introducing contamination (such as dirt and dust) to the hydraulic system while adding fluid, and never mix two different types of fluid.

Working With Hydraulic Jacks

Hydraulic jacks are powerful devices for lifting, but like any other mechanical or hydraulic system, they will inevitably require maintenance and occasional repairs. While someone with fundamental mechanical skills may accomplish some repairs, others are best handled by a hydraulic professional. Be sure to consider the options carefully before deciding on a course of action.

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