How to Service a Trolley Jack: Oil Top-Up & Air Purge Guide
Is your trolley jack struggling to lift to its full height? Does the handle feel "spongy" or offer no resistance when you pump it? These are classic signs that your jack needs a quick service. Maintaining your hydraulic equipment isn't just about performance—it’s about safety. In this guide, we’ll show you how to check your oil levels and purge trapped air from your SGS trolley jack to get it back to peak condition.
Watch the Step-by-Step Video Guide
Why Your Trolley Jack Isn't Lifting Properly
Hydraulic jacks work on a simple principle of fluid pressure. If that pressure is compromised, the jack fails. The two most common culprits are:
- Low Oil Levels: Without enough hydraulic fluid, the piston cannot reach its full extension.
- Trapped Air: Air is compressible; oil is not. If air gets into the system, the handle will feel "bouncy," and the jack won't hold a steady lift.
Tools and Materials Needed for Maintenance
Before you begin, gather these basic supplies:
- Hydraulic Jack Oil: Use ISO VG 32 or ISO VG 46. (Never use engine oil or brake fluid!)
- Screwdriver: Phillips or Flathead (depending on your model’s cover plate).
- 4mm T-bar or Blunt Tool: To help seat the rubber bung.
- Clean Rag: To wipe up any overspill.
Step-by-Step: How to Check and Refill Hydraulic Oil
- Preparation: Ensure the jack is on a level surface and the lifting arm is fully lowered.
- Remove the Inspection Plate: Unscrew the metal cover on top of the jack to reveal the main cylinder and the black rubber bung.
- Open the Reservoir: Carefully pry out the rubber bung.
- Check the Level: Look inside the hole. The oil should be just covering the top of the internal piston (roughly 1/4 inch below the hole).
- Top Up: Carefully pour in your hydraulic oil until it reaches the correct level. Be careful not to overfill, as this can cause leaks later.
The "Sharp Whack" Tip: To put the bung back in without it popping back out due to air pressure, place it over the hole and give it a quick, sharp tap with the palm of your hand.
How to Bleed (Air Purge) Your Hydraulic Jack
If your jack is still "spongy" after topping up the oil, you need to "bleed" the air out of the system using the 15-pump method:
- Open the Release Valve: Turn the handle counter-clockwise (as if you were lowering the jack).
- The 15-Pump Cycle: With the valve open, pump the handle rapidly 15 times. This moves oil through the internal valves without lifting the arm, pushing air bubbles into the reservoir.
- Release the Air: Use a screwdriver to gently tilt the edge of the rubber bung. You should hear a faint "hiss"—that’s the trapped air escaping.
- Test: Close the valve and test the lift. If it still feels soft, repeat the process.
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