Hydraulic jacks come in many forms and sizes. The two main types I use are the bottle jack and the hydraulic car jack, aka trolley jack.
Most car service centers and home handymen will use a trolley jack to work on their vehicles. Over time if the jacks are not maintained they will fail. The trolley jack is just a bottle jack on its side.
In this post, we will go over how to fix a floor jack that won’t lift and what causes them to fail. This is a jack I located in a scrap yard that wasn’t holding pressure. Often it will be a quick fix like a top-up of hydraulic fluid.
Table of Contents
- 1 How to fix a hydraulic jack
- 2 Hydraulic jack oil substitute
- 3 What causes a hydraulic jack to fail?
- 4 Hydraulic jack problems and solutions
- 5 Conclusion
How to fix a hydraulic jack
If your hydraulic jack is not working it is best to first clean the outside of the jack and drain the internal jack oil. This can be done by locating the rubber plug and removing it. Some jacks may have a small screw in the body of the jack housing that can be unscrewed.
Once this plug is removed drain all of the oil and dispose of it.
Use a small tube and funnel to top up the hydraulic jack. I have found that a syringe with a small tube works the best.
Top up the hydraulic jack with jack oil or transmission fluid. Don’t use any other fluid like brake fluid or engine oil. It will damage your bottle jack.
The correct oil level should be shown on the bottle jack near the nameplate. For trolley jacks, the oil level will be at the base of the rubber plug or screw. If there is too much fluid it will over-pressurize the system and leak out the seals.
Leave the oil fill plug off at this stage and open the air bleed screw valve. This is the screw that will lower the trolley jack. Make sure it is fully lowered before bleeding the system. You will need to now pump the jack at least 10 times. The jack should not rise up but will purge the air out of the system.
Close the air bleed valve and pump up the jack to full height. Make sure the hydraulic jack can reach the full height. If not it will need more fluid. Open the air drain valve and lower the jack. Top up again and bleed the system as before.
Reinstall the fill plug and your bottle jack is now ready for use. Congratulations you have now fixed a hydraulic jack.
Check out our video on how to top up a hydraulic car jack with transmission fluid.
Hydraulic jack oil substitute
Reading directly from the nameplate of my well-used trolley jack it says: When adding or replacing oil in the Hydraulic jack always use a good-grade hydraulic fluid, transmission fluid, or turbine fluid. Avoid mixing different types of oil fluids. Do not use brake fluid, alcohol, glycerine, vegetable oil, solvent, or engine motor oil.
Can I use motor oil in my hydraulic jack?
No engine oil is not the correct viscosity and while it may work temporally the engine oil will derate the jack. Damage can also be caused to the internal seals and o-rings due to the properties of some engine oils.
What causes a hydraulic jack to fail?
The two main reasons a hydraulic jack will fail are low oil level and overloading the hydraulic jack.
All hydraulic jacks will have a nameplate that will show their lifting force power. Overloading a floor jack will cause the seals the fail and can be dangerous.
A small amount of leakage over time from the seals is normal. This is why they will require a top-up of hydraulic fluid every now and then.
Hydraulic jack problems and solutions
The hydraulic jack won’t pump up
There could be a couple of reasons your hydraulic jack won’t pump up such as:
- Bleed valve open.
- Low hydraulic-oil level.
- Leaking seals.
- Air lock in the system.
- Bent piston shaft.
- Old oil.
Try topping up the hydraulic jack first with fluid to see if it will pump up before doing a service on the jack.
How do you fix a hydraulic jack that won’t lift?
The main cause of a hydraulic jack that won’t lift is due to lack of internal oil. This can be quickly proved by topping up the fluid level to the recommended levels and bleeding the system.
Another reason is the hydraulic jack is underrated for the load. Use a stronger jack.
Be sure to check that the jack is not bent or has any damage to the shaft or structure. If there is any damage the jack must be disposed of.
How do you fix a jack that won’t go down?
There could be a number of reasons why a jack won’t go down.
- Overloaded hydraulic jack causing damage to the structure.
- Air lock in the system.
- The wrong type of hydraulic fluid.
- Bleed air valve blocked or damaged.
Bottle jack leaking at the pump
A bottle jack is operated by mechanic force pushing a small piston up and down. There will be a small o-ring inside the piston housing that will be preventing oil from leaking out and air from leaking in.
Over time this o-ring will wear out and will need to be replaced. This is an easy job requiring only a spanner and a small screwdriver to pick out the small o-ring.
Every car owner should have a trolley jack in their shed. In fact here is a list of the tools I recommend every man/woman should have in their garage. It makes working on cars so easy, even if it is just used to change a car tire they are well worth it.
Make sure to maintain them and top up the oil every few years. Your hydraulic jack should last a lifetime of use.
Let me know in the comments if you have any issues with your bottle or trolley jack and I will help you out.
I am a qualified Industrial Electrician for the past 20 years and I love to share my knowledge on home repair jobs.
I love fast toys like Motorcycles, Cars, Jetskis, and Boats so writing about them is easy.
To keeps costs down I do all my own mods, repairs, and servicing. These skills I want to share with everyone. DIY is a skill everyone can learn.