Is it safe to use a hydraulic jack as a stand? If not, why?

Question

"If a jack can lift a load, surely it can withstand the load for extended periods of time?!"

I've come across some conflicting ideas regarding this subject:

• The user guide for my low-profile hydraulic jack warns against using it as a stand for static load-bearing duty. Paraphrased, it says that the jack should be used for no longer than necessary and should not be used for extended periods of time.

• I frequently see roadside mechanics using these jacks to raise vehicles while they work on them (not that I deem them to uphold standards of safety, but it seems to work for them).

• These jacks are typically designed such that it is difficult to release them accidentally.

• Unless the seals in the jack are shot, I don't see how the load would cause the jack to "sag" over time.

Is there some unbeknownst-to-me reason which explains why a jack makes for a poor stand?

Answer 1

There is no such thing as "absolutely, perfectly, 100% safe."

Each tool has its proper and improper uses, and each works either in parallel with other tools to increase safety and dependability, or in series with other tools ultimately reducing safety and reliability.

Will a hydraulic jack hold up a car safely? That depends on the level of risk you're willing to take. In a hydraulic jack there are several failure modes:

1. Structural failure (metal fatigue, fastener failure, weld failure)
2. Slipping, falling
3. Seal
4. Valves (3 - release, and two one way valves)
5. Improper assembly/maintenance/fluid

Further, some of these are slow, almost imperceptible failure modes. If the seal or a valve leaks slow enough that you don't notice, you might start work, not discovering until too late that the vehicle is lowering and finding yourself unable to extract your body from the slowly lowering vehicle. If you're lucky you can call for help. If not...

If you have confidence that all of these are acceptable risks, then sure, for your definition of safe perhaps a hydraulic jack is "safe". I wouldn't trust my life with it, I wouldn't recommend it to any others, but if it's just you then not even the government can force you to employ better safety practices.

Let's look at the jack stand failure modes:

1. Structural failure (metal fatigue, pin/ratchet failure, weld failure)
2. Slipping, falling

There's simply not too much that's safer than a jack stand in terms of supporting a vehicle... except more jack stands.

For me, though, this still isn't safe enough. One jack stand means one failure - thought perhaps unlikely - could result in injury or death. So at minimum I continue to use the hydraulic jack and a jack stand, but more often than not I'll use two jack stands for each lifting point and remove the hydraulic jack simply because it takes up so much room.

What you really need to determine to answer your question is what is your level of acceptable risk, and what's the cost. If you experience a failure, what's the cost of the failure? Given that your life and limb are involved, the cost of failure is so high that, for me, the extra time and cost of setting up a jack stand is always worth it.

Answer 2

TL DR: Nope, I'd say not.

When I was a young man, my Dad always told me, "Use the tool which is designed for the job." For instance, if you are trying to remove a bolt out of your suspension holding an A-Arm, you wouldn't use a body hammer to move it out, you'd use something with a little more heft, like a 5lb sledge or something similar. I'm sure if you used the body hammer, you could eventually get it out, but it's really not meant for this type of work.

Just like the hammer, the jack is the same. It's intended purpose is to lift the car when you need it. Just as you stated, a jack can have a catastrophic failure when you expect it least. Whether it's a seal or what have you, the consequences would be devastating if you were under the vehicle. Things would happen so fast, you'd not be able to get out of the way. Then most likely you'd be trapped. The proper tool for the job is the jack stand, which is meant to keep the vehicle lifted after the hydraulic jack has lifted it.

Another thing to think about is not accidental release, but improper closure of the release valve. I've used jacks before which when I started jacking it, realize the release valve was not fully closed. These, while lifting the vehicle, would also start lowering at a very slow rate as the pressure was released through the valve. I can imagine a situation where the person doing the jacking might not close it enough, then it start lowering at a very slow rate which may be imperceptible. The person then gets under the car as it starts lowering every so slowly. If the person didn't realize it soon enough, they would then be trapped under the vehicle suffering a very slow painful death. Along the same lines, if the release valve was slightly damaged or worn. In either scenario, the jack would lift the vehicle, but wouldn't be holding it in place.

Answer 3

No, I thought it could as well. One time I had a Corolla up in the air while I battled with a speedometer cable (which meant I was going in from the top of the car, underneath, and through the wheel arch). I walked away from the car to get a spanner, I came back and I was looking at where to remove a bolt. I then noticed the car was very low down.

The jack had collapsed, and neither me nor my friend heard it.

It's just not worth it. Axle stands aren't expensive, and they're a whole lot cheaper than your life.

EDIT: To clarify what I meant by "collapse", when I jacked the car up the arm was totally in the air. When I noticed it had collapsed, the arm had moved down to the normal default position. I then started to jack the car up, and as I pumped it up, it would stay up for a few seconds, then slowly sink back down. Internally a seal had popped so it wasn't maintaining pressure.

Answer 4

NO, and I don’t understand why you don’t refer to standard workshop practise which is to lift the vehicle and then put proper stands under it.

Sadly there are too many accidents of either vehicles or tipper trailers falling due to the failure of hydraulics and injuring or killing people.

Don’t rely on hydraulics to keep the mass in the air: stands or chocks or a physical blocking device...

Answer 5

Stands are simple mechanical devices in the sense that typical failures (cracks, bends) are easily observable by a simple visual inspection. That's what makes them inherently safe.

A hydraulic jack on the other hand is sophisticated enough to have hidden failure modes (leaky seals / valves, etc.) which are not instantly obvious and can be easily overlooked.

In the end, it's the amount of risk that you take that matters. If you do DIY repairs on your car, you can afford the risk of accidentally breaking it down (if you don't, you should know that you're taking it anyway). So, if the additional risk of the jack failure will result in damage only to your car, you may be willing to take it. The problem starts when you're also risking your life by not using the stands, perhaps without even realizing it.

Answer 6

No it's not the same as a jack stand or even a brick or a tire on its side.

My primary fear/experience is that a jack will tip. Adam Davis explains the risk of slow leakage, which is a thing, but your more direct risk is of the jack toppling over. Look at the design of a jack stand: it's wide at the bottom and has no wheels. Now look at a jack. Other than 4+ ton floor jacks most of the rest of them are proportionally very narrow and even wide floor jacks have wheels, which means they're not made to sit still.

To the point of it lowering accidentally, jacks and jack stands both move up and down, but a jack stand has a physical catch that must be moved out of the way in order to let it lower. The same is true of hydraulic lifts in shops too. They typically -- if not all -- have physical catches that must be moved in order for the lift to lower. Jacks do not have this safety.

If your jack does have physical catches and it's also not narrow and therefore prone to tipping over then I'd say SURE use it.

But I'd put a jack stand under it too ;)

Answer 7

Hydraulic jack seals blow.

Because hydraulic jack seals blow one should never put body parts under a load (vehicle) raised with a hydraulic jack.

Let me state that again so that it sinks in: Hydraulic jack seals blow.

Using jack stands is like wearing seat belts. It might take years until you get into a car accident or see a jack seal blow. But after it happens once, you'll make sure that you're prepared next time. And next time will happen.

Answer 8

It's not safe.

The probability for a jack to lose pressure slowly and even rapidly due to extreme failure is exponentially higher than a welded jackstand coming apart.

Also there's the argument that jacks do not have a equal footprint meaning they are more susceptible to tipping over one way over another. Jackstands don't have this issue, as the base is uniform.

You are also relying on one piece of equipment that wasn't designed to SUPPORT the vehicle for extended periods of time, instead of a piece of equipment (JACKSTAND) that is designed to HOLD the vehicle for extended periods of time.

Jackstands have less failure points, are better designed to prevent tipping, and using multiple jackstands provides the safest and lowest risk possible of being crushed by a vehicle.

Now if you are just changing a tire on the side of the road and aren't getting under the car, sure.....jack away. If the car falls there's rarely any damage done which is why manufacturers supply jackscrew type jacks and it says not to get under the vehicle even with those.

Answer 9

You'll see it done. It's not as safe as using a stand. There are more ways for a jack to fail than for a stand to.

You'll also see cars propped up on a pile of bricks. That isn't as safe as a stand either.

But stands can fail too. Nothing is 100% safe, other than not being under the car at all. But I expect you're under there to fix something that will make driving it safer? Best not go near the car at all!

"If a jack can lift a load, surely it can withstand the load for extended periods of time?!" is very flawed reasoning. Might as well say "If a man can lift it, he can hold it up for ever." Patently untrue.

Answer 10

NO!_Not Safe_very Unsafe! Wonderful detailed explanations in this thread. If the work you're doing on your vehicle requires you to get under the chassis then you Need a Jacks-stand. Borrow or buy 2 of them and use them. Don't let you life become a statistical data point proving the everyone should use jack-stands when doing anything at all under a car that has been jacked up by any kind of jack! Would you let your daughter or son under that car without jack-stands? I would sincerely hope not.