To release a hydraulic jack, you turn the release valve counterclockwise, slowly, until the ram begins to descend. The valve is typically located where the pump handle connects to the jack body, and on most floor jacks it’s controlled by turning the handle itself or a separate knob. The key is going slow: a small turn is all it takes, and opening the valve too quickly can drop a heavy load in an unsafe, uncontrolled way.
How the Release Valve Works
When you pump a hydraulic jack, you’re forcing fluid from a reservoir into a cylinder, which pushes the ram upward. The release valve seals that fluid in place, holding the load. When you turn the valve open, you create a path for that pressurized fluid to flow back into the reservoir, and gravity pulls the load down.
The amount you turn the valve controls how fast the fluid returns, which directly controls how fast the load descends. A quarter turn is usually enough to start a slow, controlled descent. If you crank the valve wide open, the fluid rushes back all at once and the load drops fast. That’s where injuries happen.
Step by Step: Releasing a Floor Jack
On most hydraulic floor jacks, the release valve is built into the handle socket. You insert the handle and turn it counterclockwise. Here’s the full sequence:
- Confirm your support. Before you release the jack, make sure the load is resting securely on jack stands, blocks, or whatever permanent support you’re using. The jack itself should never be the only thing holding weight while you’re under a vehicle.
- Fit the handle into the valve. Insert the pump handle into the jack’s socket if it’s not already in place.
- Turn counterclockwise, slowly. Give the handle a quarter turn at most. You should hear or feel the fluid begin to move, and the saddle will start to descend.
- Control the speed. If the load drops too fast, tighten the valve slightly (turn clockwise) to slow things down. You want a gradual, steady descent.
- Lower fully and close. Once the load is all the way down and the weight is off the jack, turn the valve clockwise to close it. Remove the jack.
For bottle jacks, the process is the same, but the release valve is usually a separate knob or screw near the base of the cylinder rather than part of the handle. You’ll turn it with the handle, a wrench, or by hand depending on the model.
Safety Before You Release
Serious crushing injuries result from improper jack use, and the release phase is one of the most dangerous moments. A load that shifts or falls during descent can tip a vehicle off the jack entirely.
Before releasing, check that the jack is still sitting straight. If it has leaned at all during the lift, the load can shift sideways when you open the valve. Make sure the surface under the jack is flat, level, and solid. On soft ground, a wide board under the base prevents the jack from sinking or tipping as weight transfers. If the vehicle is self-propelled, it should be in park (or in gear for a manual transmission) with the parking brake set and at least one wheel on the ground chocked with a block.
Stand to one side while releasing, not directly in front of or behind the jack. On mechanically operated jacks, the handle can kick or pop up during lowering. Never straddle the handle.
Lowering Onto Jack Stands
If you’re transferring a vehicle’s weight onto jack stands rather than lowering it to the ground, the release process requires extra care. Position the jack stands directly under the vehicle’s designated lift points before you start lowering. Check your owner’s manual for those specific locations.
Open the release valve just enough for the vehicle to descend slowly onto the stands. The weight needs to come down flush on top of each stand. Problems happen when the jack is tilted or the vehicle’s weight lands off-center on the stand, which can cause it to kick out. Once the stands are bearing the full weight, you can lower the jack the rest of the way and slide it out. Give the vehicle a firm push from the side to confirm it’s stable on the stands before you get underneath.
Cold Weather Affects Descent Speed
If you’re working in a cold garage or outdoors in winter, your jack may behave differently than expected. Hydraulic fluid thickens as temperatures drop, which makes it flow more slowly through the valve. At near-freezing temperatures, the response can be noticeably sluggish. The ram may hesitate before it starts to move, or descend unevenly.
This isn’t dangerous in itself, but it can catch you off guard if you compensate by opening the valve wider than usual. Once the fluid warms up from use, the viscosity drops and it flows more freely, so a valve setting that seemed barely open enough in the cold can suddenly allow a much faster descent. Start with small adjustments and be ready to tighten the valve back if the speed picks up.
When the Jack Won’t Release
If you turn the release valve and nothing happens, a few common problems could be at play.
A stuck one-way valve is the most frequent cause. This internal valve is supposed to open when you turn the release knob, but corrosion or debris can seize it in the closed position. You may be able to free it by working the valve back and forth (open and closed) several times. If that doesn’t work, the valve needs to be disassembled and cleaned or replaced.
Air trapped in the hydraulic system can also prevent proper lowering. Air compresses where fluid doesn’t, so it creates a spongy, unresponsive feel. To bleed air from the system: raise the jack to full height, loosen the fill/bleed screw (located on the cylinder, not the safety valve) about halfway, then lower the jack fully. You should see air or fluid escape. Tighten the screw, raise the jack to full height again, and repeat. Do this two or three times until the action feels firm and consistent. Top off the fluid through the bleed screw hole before you finish.
Low fluid levels cause similar symptoms. If the reservoir doesn’t have enough hydraulic oil, the jack can’t build or release pressure properly. Check the fluid level through the fill plug and add hydraulic jack oil (not brake fluid, not motor oil) until it reaches the bottom of the fill hole.
A damaged seal inside the cylinder can also prevent the ram from descending, because fluid can’t flow back through its normal path. Worn seals typically also cause the jack to slowly sink under load. Replacing seals is possible on many jacks, but at the price point of most consumer floor jacks, replacement is often more practical than repair.