The symptoms of a failing jack are that when you pump the handle up, the jack raises, but it doesn’t stay up, or it cannot hold weight. Here are some ways to diagnose and repair a jack that leaks down or won’t lift. In most cases, the jack will need hydraulic fluid added. It may also need some seals replaced. In this article, we will show you how to do both.
When I was a kid, we had a wide assortment of bottle jacks and cheap Harbor Freight floor jacks. They never worked for more than a couple of years, so dad would buy another one. One day, he had an old-timer show him how to add hydraulic fluid. We spent an afternoon topping off our jacks and instantly had a large, working collection of jacks.
That was a fun winter afternoon activity.
What Causes A Hydraulic Floor Jack That Won’t Lift?
In all cases, a failing floor jack is a result of a lack of hydraulic pressure. This could be from low levels of hydraulic fluid or an internal or external seal leak. This guide will help you find and fix common leakage points.
Items To Check:
See Also: What To Do When You Car Falls Off A Jack
What Is The Lifting Capacity?
Hydraulic floor jacks offer a lifting capacity from 2 tons up to 15 tons. The larger the jack, the more you can lift. You can lift a tiny hybrid car with a larger floor jack, but you should not try to lift a large truck with a tiny, undersized jack.
Each jack has a limited lifting capacity. If you exceed that lifting capacity, the jack may collapse and be permanently damaged.
Check the weight limit on each jack and compare that with the weight of the vehicle being lifted. A Ford F150 weighs about 2 tons. It is rare that you would need to lift the entire car, so any jack with a lifting capacity of 1 ton or greater should be able to lift that truck.
If a jack has been overloaded, the jack may no longer be safe to use. Sometimes the seal will be permanently damaged by overload and will need to be replaced.
Check The Hydraulic Fluid Level
The fluid level should be within the manufacturer’s guidelines. All floor jacks are designed with the fill hole on the side of the jack — not at the very top. This prevents overfilling of the jack. Because of this design, it is more likely that jack will deal with a low fluid level problem than with an overfilling problem.
The low fluid level may prevent a jack from fully raising. It may also cause the jack not to lift, as the fluid is unable to build sufficient pressure.
Because a hydraulic jack works as a closed loop system, the only way for a jack to have low fluid is if there is a leak. It is common for jacks to lose fluid past their seals with use and age. This fluid loss will increase as the jack ages until it reaches the point that it needs all of the seals replaced in a full rebuild.
How To Check The Hydraulic Fluid On A Floor Jack
Checking the oil level in a jack should be simple: remove the oil fill screw and add oil until it reaches the bottom edge of the fill plug. Replacing low hydraulic fluid will fix most hydraulic jack problems.
However, on most floor jacks, this fill plug is underneath the arm of the jack. This means that the jack needs to be raised, and then a long, skinny funnel is used to reach the fill port. In a lot of cases, the jack needs to be disassembled, and the inner pump needs to be removed so you can access the fill plug.
Thankfully, this task only needs to be performed once every five years or so, depending on the jack’s age.
When working with your jack, it is helpful to have an owner’s manual. In most cases, you can search for one by searching your jack model and the phrase “pdf” in Google. This will give you vital information on the manufacturer’s specifications for fluid type and viscosity.
Hydraulic jacks need ISO 22 oil. It can easily be purchased over the counter at Autozone, your local farm supply store, or online on Amazon. In most cases, you will only need a couple of ounces, but you will most likely be sold a large bottle of it.
Hydraulic fluid will contain rust inhibitors. Since the hydraulic fluid helps to lubricate and protect the inner working components of the pump, it is worthwhile buying a premium lubricating oil brand like STP that contains additives to protect your pump.
Keep in mind that air compressors use an ISO 100 hydraulic fluid, which is not suitable for floor jacks. Some YouTubers have talked about using transmission fluid. If you are going through the hassle of filling your jack, it makes sense to invest the extra 15 minutes in ordering the right jack.
How To Bleed Air Trapped In A Hydraulic Jack
Too much trapped air in the hydraulic line will prevent the hydraulic fluid from building pressure and will cause the jack to leak down and lose its lifting ability.
If you add fluid, but the jack is still not jacking up or holding pressure –especially if it drops a little when pressure is applied and then stops — it might have trapped air that needs to be bled out.
Bleeding air out of a jack is simple; add fluid and then raise and lower it a few times, adding fluid after every time until you have added enough fluid to work the air bubbles out of the jack.
Look For Leaks
Sometimes a jack is leaking at the rubber seals, causing a puddle on the floor. Those leaks are easy to identify.
More commonly, however, is the situation where the relief seal (the one you turn to lower the jack) is not seating well and is allowing hydraulic fluid to slip by. This is especially common in slow overnight leaks, where the jack slowly lowers itself overnight.
Whether it is an internal or an external leak, the jack will need to have seals replaced.
The Overload Valve Has Been Tripped
Many floor jacks have an overload valve that prevents them from lifting a load that is too heavy for their rating. This bypass valve or safety valve allows the jack to release the additional pressure and prevent injury.
The frustrating thing is that you may be trying to jack a vehicle, but the jack will not move.
There is a screw head near the back of the jack where the handle inserts. Normally there is a warning sign to not mess with this screw head and a plastic cap covering it. This screw head controls a ball bearing and a spring that regulates the max lifting capacity of the jack.
Sometimes, this screw will leak down, making it difficult for the jack to hold pressure as the fluid leaks past it.
By disassembling your jack, you can remove this screw head and look for any bad seals that are allowing hydraulic fluid to slip by.
Before removing this overload screw, tighten it all the way and count the number of turns it takes to tighten the screw head. This will let you know how many turns it will take to recalibrate this overload valve when you remove it.
Even a small amount of dirt in this valve area can cause the jack to leak down.
Inspect The Release Valve
To inspect the jack’s release valve, you simply unscrew the release valve all the way. As it threads out, there will be a small ball bearing down in the bottom. Additionally, when you flip it over to get the ball bearing out, all of the hydraulic oil will drain out, and you will need a catch can to capture this oil.
From there, check the ball bearing and the relief valve threads for cleanliness.
If the jack still doesn’t hold pressure, the seal may need to be replaced. At this point, you are looking at a full rebuild.
Rebuilding A Floor Jack By Replacing Inner Seals
When you repair or rebuild your floor jack, you are accepting the risks of repairing a jack. Most people use their jack to lift heavy cars, and a jack should always be paired with jack stands to protect the user when they are under a vehicle.
If your jack is still not holding pressure, you might decide to give it a full rebuild. In our throw-away society, it is rare to repair an item instead of just buying a new jack. However, my blog tends to attract people like myself who like to fix things for the joy of fixing them.
Look for a rebuild kit online. It should consist of seals, o rings, and some cotter pins or c-clips.
Take pictures along each step. It is easy to forget which way things originally went together.
Step 1: Remove The Inner Spring
Physically pull or pump the floor jack up, and prop it in the raised position with a block of wood to allow you room to work underneath it. There is a spring attached to the hydraulic pump that helps bring it back down when releasing pressure. Start by taking a pair of pliers and disconnecting that spring.
Step 2: Remove The Handle
There are two bolts, one on each side of the handle at its base. Start by removing this handle and setting it to the side so that you can more easily maneuver the jack as you work on it. We do this in the second step since your jack may have enough pressure to allow you to raise it by pumping the handle.
Step 3: Lower the Jack Arm and Turn On the Side
Once you have lowered the jack arm again and laid it on its side, you are able to access the full pump and begin removing the wheel bolts. The Wheel bolts go through the frame, the wheel casters, and then hold the jack pump into place. Depending on the model, there may still be two smaller bolts on the inside that need to be loosened. Generally, the jack portion will be attached to the pivot points with cotter pins or c clips.
Step 4: Drain the Fluid
The jack is full of fluid. Remove the top cap and the relief valve screw and attempt to drain all of the fluid from the jack.
Step 5: Disassemble The Jack
It is handy to have a vise to hold the jack in for this as you disassemble it. The large nut at the “top” of the jack needs to be removed and will require a large crescent wrench.
Once removed, all of the parts disassemble a lot like nesting dolls. The different pistons slide inside each other and have an exact orientation. Take notes and pictures to make sure you can reassemble it correctly.
Step 6: Replace the Seals and Reassemble The Plunger
Once the seals are accessible, it is only a matter of replacing each seal carefully. The entire process is straightforward. Once Reassembled, the jack needs to be refilled with hydraulic oil and tested.
Never Trust Floor Jacks
Even when fully repaired, a jack should never be used for long periods of time and should always be used alongside a jack stand. Jack stands are an essential safety item that protects the user in the event of jack failure. A jack is a lifting device only and should not be used to hold heavy weight.