When should I bleed a hydraulic jack?

A bottle jack needs bleeding from time to time, especially if you use the tool regularly or have transported the tool recently. When the jack has got air in its system, it won’t work properly and will not be able to lift a load. You need to bleed a hydraulic jack when it cannot lift as heavy load as stated by the manufacturer, or it slowly losses height when the load has been lifted, but in most cases, if the system has air in it, the jack simply won’t lift a load. The process of bleeding a jack is pretty simple and can be done at home.

How to bleed a hydraulic jack?

To bleed a jack you will need a flathead screwdriver for most jacks and preferably an instruction manual of your jack, although you can bleed the jack without the instruction manual because for most jacks the bleeding process will be similar.

As mentioned, the process is very easy, to bleed a jack follow these steps:

  1. If the jack is attached to an engine hoist, I suggest removing it from the hoist before bleeding it;
  2. Take a pump handle and open the bleed valve by turning it counterclockwise. The bleed valve is usually located on the bottom of the jack, next to the pump handle socket. Wait till the ram is lowered to the lowest position;
  3. Remove the oil fill plug which should be located in the middle on the side of the jack. You may need to use a flathead screwdriver to remove the plug;
  4. Insert the jack’s pumping handle into the handle socket and pump the handle quickly for about 10-20 strokes (how much times you should pump the handle will usually be indicated in the owners manual of the jack, but generally 10-20 is going to be enough). This pumps the oil throughout the system from the oil reservoir to the high-pressure system and back to the reservoir through the bleed valve and takes the air from anywhere in the system with it, so any trapped air from the system ends in the top of the reservoir and goes out of the reservoir through the oil fill plug hole;
  5. Check the oil level in the jack, before placing the oil plug back into the cylinder. Fill a hydraulic oil into the jack if necessary;
  6. Place the rubber oil plug back into the cylinder;
  7. Close the release valve;
  8. Pump the jack to the maximum height and check if everything works properly.
  9. Reinstall the jack back to the hoist. Test the jack with a lower capacity load before using it to lift a heavy load. If jack still does not work properly, repeat the steps 1-7.

If these air bleeding steps do not work for you, try this method instead that should get all air bubbles out of the jack.

Billy Miller
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