Air Jack Slow or Tipping? Air Bag or Air-Hydraulic, Explained

Your air jack crawls up, stalls halfway, or the bag bulges sideways and starts to tip the load. Before blaming the jack, check the air, the ground and where the load sits.

Here is how bag and air-hydraulic jacks lift, what air they need and how to cure a slow lift. PartsForMachines lists 36 air jacks and vehicle lifts from Sealey, Draper, Chicago Pneumatic, SIP and Sykes Pickavant, rated from 1.5 to 100 tonnes.

Do Air Bag Jacks Really Work, and Will They Lift Straight?

Yes: a modern bag jack lifts fast from very low, and rises straight if the load is centred and the ground firm and level. The bag jacks we stock have an internal telescopic guide: the PAFJ3S 3-tonne air fast jack has a telescopic interlocking steel core and starts at 135mm, and its maker quotes 25 seconds to reach its full 450mm.

If the bag bulges and leans, check the set-up. On soft or sloping ground any jack can tilt and the saddle can slip, so work on concrete where you can and centre the jacking point on the saddle. If it still leans with no load on a flat floor, stop using it until it has been checked.

Air Bag or Air-Hydraulic: How Does Each Lift, and Which Do I Need?

A bag jack suits cars and vans; trucks, tractors and plant call for an air-hydraulic jack. A bag jack such as the CP88221 2-tonne balloon jack feeds compressed air straight into the bag, so it is light and quick; the bag jacks we stock are rated 2 or 3 tonnes.

An air-hydraulic jack uses the air to power a hydraulic system that pushes the ram. That makes it heavier (a 30-tonne high-lift truck jack weighs 126kg, against 20kg for the PAFJ3S bag jack), but it can lift up to 100 tonnes.

Why Is My Air Jack Slow, or Why Does It Stop Partway Up?

Check the air first, then the load, then the hydraulics. A long, narrow hose or undersized couplings can starve the jack, so inlet pressure drops once it runs. Keep the hose short, with a generous bore and matching fittings, and check the compressor keeps up.

If it rises then stops, check the weight against the stage reached: telescopic jacks carry less as they extend. The YAJ10-40LELR telescopic truck jack takes 40 tonnes to 302mm but only 10 tonnes at 396mm. On air-hydraulic jacks, low oil or air in the hydraulics can also stop the lift.

What Air Pressure and Compressor Does an Air Jack Need?

Most air jacks need about 7 to 12 bar (100 to 174psi) and, where the figure is given, 7.5 to 11.5cfm of air while lifting. Bag jacks such as the CP88 models run on 7 to 10 bar, and heavier truck jacks often want 8 to 12 bar. Compare them with what your compressor actually delivers.

Big jacks can need a big compressor: the YAJ201 needs one above 3hp. Draper truck jacks have a 1/4in BSP inlet and come with a connector. No airline? A dual-control jack such as the AM20S 20-tonne manual/air bottle jack can also be pumped by hand.

What Should I Check Before I Order?

• the weight at your lifting point against the jack’s rating at the height you need
• the gap under the lowest jacking point against the minimum saddle height
• the lift range you need, including the extensions supplied
• your compressor’s pressure and air delivery against the jack’s figures, plus the inlet fitting
• where it will work: floor, pit, ramp or roadside

Browse the air jacks range, or contact the PartsForMachines team by WhatsApp, telephone or email with the vehicle and its weight.

Product options, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

How low can an air jack get?

The CP88221 bag jack starts lowest, at 115mm, and the PAFJ3S at 135mm. Low-entry truck jacks start from about 125mm, such as the YAJ10-40LELR at 130mm. Measure under the lowest jacking point before you choose.

What are the extensions for?

They fill the space between the saddle and the jacking point, so more of the ram’s stroke is left for lifting. The YAJ201 comes with 20, 50 and 100mm extensions, and several low-entry truck jacks come with 45 and 75mm ones.

How do I lower an air jack under control?

Use the jack’s own control and lower it slowly. Several truck jacks have a dead man’s handle that also helps control the lowering speed. The 02079 has a ‘Slow Down’ valve, and bag jacks such as the PAFJ3S have a valve for quick, controlled lowering.

Do I still need axle stands once it is up?

Yes. A jack is for lifting, not for holding a load while you work: never go beneath a vehicle held only by a jack. Lower it onto rated stands, on firm, level ground, before you go underneath.

Can I use an air jack in a pit or on a ramp?

Yes. An air jacking beam such as the SJBEX200A runs along the pit or ramp, lifts from 95 to 300mm at 90 to 145psi and has a 2-stage mechanical safety lock. Compact bag jacks such as the PAFJ3S also suit car ramps.

How do I look after an air jack?

Drain the compressor tank daily, because water in the air line causes corrosion and wear. On air-hydraulic jacks, check the oil level with the jack fully lowered and follow the manual for oil type. Some models, such as the AM20S, have service kits.

What does the overload valve do?

It protects the jack and the vehicle from overloading. Several air jacks have one, such as the PAFJ3S, AM20S and 02079, so if a jack will not lift a heavy load, check the weight against its rating before suspecting a fault.

Is a cheap air bag jack worth buying?

Judge it on features rather than price: look for an internal telescopic guide and an overload safety valve, as on the CP88221, and a rating above the weight at your lifting point.