A hydraulic floor jack is used to lift heavy vehicles to be able to work underneath them. It works as a result of fluid being compressed through cylinders on the jack. As the handle is pumped, the cylinders press the pressurized hydraulic fluid, giving the force necessary to lift the vehicle. When a hydraulic floor jack is not operating properly, it can be repaired quite easily with basic tools.
Step 1 - Clean the Device
Anytime you are going to be working on, or maintaining, your hydraulic floor jack, it must be clean before starting. If any type of debris or dirt gets into the hydraulic fluid, it can do a lot of damage to the inside of the cylinders. Use shop rags to wipe down the cylinders thoroughly before you open any.
Step 2 - Remove Plug on Cylinder
When this machine is not working properly, most of the time it is a failure in the plug or dirt in the hydraulic fluid. Look for the rubber plug on top of the cylinder and use a screwdriver to carefully pry it up. If the plug is damaged, you will need to buy a new one to replace it later.
Step 3 - Drain Hydraulic Fluid
Set up a bucket under the hydraulic floor jack and turn it so that the fluid drains out. Once the cylinder is empty, look inside to make sure that there isn't any more debris laying around that needs to be cleaned up. If there is some, blow it out with some compressed air.
Step 4 - Replace Fluid
Once the cylinder is clean, you'll need to put need to pour new fluid in with the aid of a funnel. The amount you will use will vary depending on the size and the make of the floor jack. Regardless, you want to make sure that the cylinder is full. If you do not have access to hydraulic fluid, you can use 5W-30 motor oil as a substitute, but you should replace it with the correct substance as quickly as possible.
Step 5 - Replace Rubber Plug
Check the rubber plug, new or old, before you set it back in place. Clean it off with a rag to make sure there isn't any dirt on it. Then, set it into the hole in the cylinder and press it firmly. The plug should be seated flat without any type of wrinkle in it which can cause air to leak into the cylinders.
Step 6 - Test
You should not have any other problems once the fluid has been replaced, but to make sure, you should test the floor jack several times before putting any considerable weight on it. Lift the arm several times to make sure the pressure holds. Then, place the jack under a vehicle and begin to lift it. Make sure the pressure is able to hold the weight before fully use it.