How to Use a Grease Gun with a Bleeder Valve

Load the gun, then open the bleeder valve a quarter to half turn (or press it, depending on the model) while you pump. Close it as soon as grease, not air, comes out of the vent. The valve lets air trapped in the barrel escape so the pump can build pressure and push grease to the fitting.

What a bleeder valve does

A grease gun works by pushing grease through a small pump. If a pocket of air sits between the grease and the pump, the plunger just squeezes the air back and forth. You pump the handle and nothing comes out the tip. This is called an air lock.

The bleeder valve is a small vent, usually a screw or button on the head of the gun or on the barrel end. Opening it gives the air a path out. Once grease follows the air out, you close the vent and the gun can build pressure again.

Not every gun has one. Some guns are bled by loosening the hose at the head or by pulling the plunger rod back and releasing it. Check your gun's manual if you cannot find the valve.

Before you start

A few minutes of setup saves a lot of frustration and mess. Grease guns can create very high pressure, so treat them with care.

Wear safety glasses and nitrile gloves. Grease can spray from a vent or a loose fitting.
Keep your hands and fingers away from the tip and the vent. Grease forced under the skin by a high-pressure gun is a medical emergency, even if the wound looks small. Get medical help right away if it happens.
Wipe the grease fitting (the Zerk) clean with a rag so dirt does not get pushed into the joint.
Make sure the equipment is off, parked, and cannot move. Support anything raised on a jack with proper stands.
Have a rag and a small container ready to catch the grease that comes out of the vent.

Prime the gun step by step

Priming is the stage where the bleeder valve does its work. The steps below fit a typical cartridge-loaded manual gun. Models differ, so follow your gun's manual where it disagrees.

Unscrew the barrel from the head. Pull the plunger rod back until it locks, then remove the old cartridge or empty the barrel.
Remove the cap and the foil seal from a new grease cartridge, and slide it into the barrel. Screw the barrel back onto the head by hand until it is snug.
Release the plunger rod so the spring pushes against the back of the cartridge.
Open the bleeder valve about a quarter to half turn. If yours is a push-button type, hold it down. Do not unscrew it all the way out.
Pump the handle slowly. You may hear hissing or see a little spitting at first. That is the trapped air leaving.
When a steady stream of grease shows at the vent, close the valve. Wipe off any grease around it.
Pump a few more times with the tip pointed into a rag. Grease should come out of the nozzle in a smooth, even flow.

Greasing the fitting

Once the gun is primed, press the coupler straight onto the fitting. Keep it square, because a tilted coupler leaks around the side. Pump slowly and watch for the first sign that the joint is taking grease. Many joints have a rubber boot that swells slightly when full. Stop when you see fresh grease squeeze out at the seal or when the boot firms up.

Over-greasing can blow out seals, so more is not better. Wipe the fitting and surrounding area when you finish. Old, dirty grease that gets pushed out is a good sign, and you can clean it away with a rag.

If you will be working on recessed or awkward fittings, a longer locking coupler helps keep the connection steady so you can use one hand to pump and the other to brace yourself. Release the coupler's lever before pulling it off. Some locking couplers stay on under pressure, so let the pressure drop first.

If the gun still will not pump

If you have bled the gun and still get no grease, work through the common causes below before you assume the gun is broken.

Symptom	Likely cause	What to try
Handle moves, no grease at the tip	Air lock in the barrel	Reopen the bleeder valve and pump until grease shows at the vent
Grease leaks around the barrel threads	Barrel not tightened or worn seal	Retighten by hand and check the seal for wear
Grease leaks at the fitting	Coupler is not square or is worn	Reseat the coupler, then check its seal and jaws
Pumps hard, grease will not enter the joint	Clogged or damaged fitting	Wipe it, try again, and replace the fitting if it stays blocked
Grease comes out of the valve when you pump	Valve still open	Close the valve once grease appears

Choosing a coupler that seals well

Even a perfectly primed gun wastes grease if the coupler does not seal. The coupler is the part that grips the fitting, so it affects how much grease actually reaches the joint. Our best grease gun coupler comparison lines up the options by locking style, pressure rating, and length.

Every ranked coupler on our spec sheet uses a 1/8 in NPT thread, the common size on grease guns. The ones that list a pressure rating show 10,000 psi or 12,000 psi. The gun sets the pressure you actually use, so match the rating to your gun rather than chasing the highest number. For example, the LockNLube XL is rated to 10,000 psi and is 5.5 in long, which suits recessed fittings, and it comes with a rebuild kit.

If you are deciding whether to upgrade a coupler or buy a whole gun, our best grease gun for the money page explains the trade-offs. Most of the products there are couplers and kits, so a coupler upgrade suits a gun you already own.

Storing the gun and keeping air out

Store the gun with the bleeder valve closed and the tip capped or wrapped to keep out dust. Keep a partly used cartridge in the gun, or cap it and keep it clean. Dirt in the grease wears out joints faster than skipping a service.

If the gun has sat for a long time, expect to bleed it again. Air creeps in as grease settles. When you swap cartridges, repeat the priming steps rather than pumping and hoping. Taking a minute to purge the air keeps the gun working smoothly the next time you need it.

Frequently asked questions

Where is the bleeder valve on a grease gun?

It is usually a small screw or push button near the head of the gun, where the barrel meets the pump. Some guns put it on the end of the barrel. If you cannot find one, your gun may be bled another way.

Can I take the bleeder valve all the way out?

No. Open it only a quarter to half turn. Removing it completely can let grease spray out under pressure and may cause you to lose the valve.

What if my grease gun has no bleeder valve?

A common method is to loosen the hose at the head, pump until grease shows, then retighten. You can also pull the plunger rod back and release it a few times. Check your manual for the right method.

How do I know the air is gone?

Air comes out as hissing or spitting. When you see a smooth, steady ribbon of grease at the vent or the tip, the air is out and you can close the valve.

Should I use the bleeder valve every time I change a cartridge?

Yes. Swapping cartridges lets air into the barrel, so priming with the valve each time helps prevent an air lock.