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It’s not supposed to happen. You’re trying to get a tire pressure reading or add air to your tire.

Instead, air escapes the tire valve when you put the air compressor nozzle over the tire valve stem. Your tire pressure is now going down instead of up, which wasn’t the plan!

There are two main reasons air is escaping; we will go into detail below. Briefly though.

Air is escaping because either the tire valve has dirt inside or is defective, or the air compressor nozzle you use to fill up with air is damaged.

Let’s get into the details, but before we do, try pushing down harder on the tire valve. 

It is normal for a little air to escape while pressing the nozzle over the valve. Sometimes you may lose 1 or 2 psi before the nozzle finally seats against the valve. 

Give the compressor nozzle a wiggle and listen to see if the hissing reduces at a certain angle. Often adjusting the angle at that, you present the nozzle to the valve, allows a tight seal.

Tire Valve Problem

Is your tire quite new? If so, the valve will be new too. It’s always replaced at the same time as the tire. 

Have you ever left the valve cap off? 

The cap doesn’t stop air from escaping but does protect the valve stem from dirt and corrosion. 

Almost all car tire valves are two way Schrader types and have a pin in the center of the valve. This pin, when pressed down, is designed to let air escape or allow air in. 

When you place the air compressor nozzle over the valve, it pushes the pin down, allowing air into the tire. 

The compressor nozzle should seal over the valve stem and prevent air from escaping the tire even though the pin is pushed down. 

If air is escaping, the valve’s inner workings are fine, but the valve stem – the part that you screw the cap on – may be rusted or have dirt on it, preventing a tight seal. 

Clean this area up and try again. Has that worked?

Here’s a quick tip to see if the valve is faulty. Try using the air compressor on your other tires and see if you get air escaping on these as well. 

If so, it’s not your tire valve at fault but the compressor.

A final note: If your tire has been leaking air more than the other, the valve has worked loose and is leaking slowly. 

You’ll need a special – but cheap – tool to tighten the valve. It’s called a tire stem valve tool, and they cost about $5.

Air Compressor Nozzle Problem

We have ruled out the tire valve being the problem. If air can escape the valve, air can almost always be pumped in. 

If the valve stem looks clean and non-corroded then turn your attention to the air compressor nozzle you are using to get air into your tire.

Gas station air compressors are often damaged

Gas station tire free – or paid – air compressors are renowned for being abused by motorists. 

Often the hose doesn’t retract properly, or the nozzle sits in the dirt. It probably gets used tens of times a day, and few people will take care of it the way they would if it was their own. 

If the nozzle is letting air escape have a good look at it. Is it perfectly circular, or has it got a dent in it? A small ding will stop a perfect seal on your tire valve.

Can you get a tight seal on the other tire valves? If not, this indicates that the nozzle is damaged and your tire valves are fine.

If you don’t have your own compressor, go to the tire shop. They will either allow you to use their air compressor or will top up your air for you. 

It makes perfect business sense for tire shops to do this for potential customers. They get a chance to check your tires for damage and low tread, which may mean more business for them. 

Even if your tires are fine, you are more likely to think of them first when replacing them in the future. Reciprocity

Final thoughts

Air compressors are cheap and make it really easy to inflate tires and check tire pressure at home without going to a gas station or tire shop. 

This is really useful if you have a flat and need to get air in the tire before driving to the tire shop. 

Even a short journey on a badly underinflated tire can damage the sidewall beyond repair.

Often read next: Do Tires Leak Without The Air Valve Cap? Here’s When!

In conclusion

If only one tire has air escaping, it is likely to be the valve in that tire. Clean around the outer area of the valve stem and check for corrosion. This is likely to be the cause if one tire leaks air more quickly than the others.

If all your tires leak a little when you try to fill them with air, check that the air compressor nozzle is clean and hasn’t been damaged. Many gas station ones are.

Consider buying an air compressor and pressure reader yourself. It’ll save you lots of time and hassle, and if you check your tires regularly, it will give you an early warning if a tire has a slow leak.

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