Bleeding a car jack, specifically a hydraulic floor jack, is a maintenance procedure to remove air bubbles from the hydraulic system. Air in the system prevents the jack from building pressure, causing it to feel spongy or fail to lift. The core process involves opening the release valve, pumping the handle several times, and then closing the valve to restore proper function. This is a straightforward task that requires minimal tools and can restore your jack's performance in about 10-15 minutes.
The most common symptom that your jack needs bleeding is a failure to lift a load, or the saddle rising slowly and then sinking back down under pressure. This occurs because air in the hydraulic fluid is compressible, unlike the fluid itself. Before starting, consult your jack's manual for any model-specific instructions and ensure the jack is on a level surface with the release valve fully closed.
Step-by-Step Bleeding Process:
- Prepare the Jack: Place the jack on a flat, level surface. Locate the release valve (or bypass valve), which is typically a knob or a screw located near the pump mechanism. Turn it clockwise, slowly, until it is fully closed. It's crucial to start with the valve closed.
- Open the Release Valve: Turn the release valve counterclockwise, about one full turn, to open it. This opens the hydraulic circuit.
- Pump the Handle: Rapidly pump the jack's handle up and down through its full range of motion 10-15 times. This action pushes the hydraulic fluid through the system, forcing any trapped air bubbles out through the open release valve.
- Close the Release Valve: Turn the release valve clockwise to close it securely.
- Test the Jack: Attempt to lift the jack without a load. The saddle should rise smoothly and hold its position. If it still feels weak, repeat the bleeding process. For a final test, carefully lift a light, safe load to confirm it holds pressure.
To minimize the need for bleeding, always store your jack with the saddle in the lowest position and the release valve closed. This helps keep the internal seals lubricated and prevents air from being drawn into the system. If bleeding doesn't solve the problem, the jack may have worn seals or need a hydraulic fluid refill.
| Bleeding-Related Data | Specification / Information |
|---|
| Recommended Hydraulic Fluid | SAE 10W or 20W hydraulic jack oil; general-purpose ATF (Automatic Transmission Fluid) is often acceptable |
| Typical Fluid Capacity | 3-6 ounces (approx. 90-180 ml) for a standard 2-3 ton floor jack |
| Common Release Valve Types | Knob (quarter-turn), Screw-type (multiple turns), Lever-actuated |
| Signs of Successful Bleeding | Smooth, firm lifting action; saddle holds position under light load |
| Primary Cause of Air Entry | Storing jack with saddle fully extended; running the jack low on hydraulic fluid |
| Average Time to Complete Task | 10-15 minutes for a single bleeding cycle |
| Safety Precaution | Never bleed a jack while it is supporting a vehicle. Always bleed it unloaded. |
