Air Release Bleeder Valves

Frequently Asked Questions: Air Release Bleeder Valve

What is a grease gun air release valve and what does it do?

An air release valve (also called a bleeder valve) is a small threaded fitting that screws into the grease gun head and vents trapped air that causes the gun to stop pumping. Air enters the barrel during cartridge changes and bulk loading. Without a bleeder valve, this trapped air compresses instead of pushing grease forward, making the lever feel normal but delivering no grease at the coupler. The S-ARV vents this air so grease flow resumes immediately. Available in manual (S-ARV/M) and automatic (S-ARV/A) versions.

What is the difference between the S-ARV/M manual and S-ARV/A automatic valve?

The S-ARV/M requires the operator to press a button to vent air, while the S-ARV/A vents air continuously without any operator action. The manual version gives precise control: press to open the vent port, pump until grease appears, then release to seal. This minimises grease waste. The automatic version uses a self-actuating mechanism that opens for air (low density) and closes for grease (high viscosity), requiring no intervention. Choose manual for occasional cartridge changes; choose automatic for high-reload fleet environments.

How does the air release valve eliminate air locks?

The valve provides an escape path for trapped air that would otherwise compress in the barrel and block grease flow. In a sealed grease gun head without a bleeder, air has nowhere to go except back through the grease column (which is extremely slow). The S-ARV creates a direct vent from the head chamber to atmosphere. Air, being less dense than grease, rises to the valve port and escapes. Once the air is purged, grease fills the chamber and normal pumping resumes. The manual version requires the operator to open and close the vent; the automatic version handles this continuously.

What thread size is the S-ARV air release valve?

The S-ARV is manufactured in three thread options: 1/8" BSPT, 1/8" NPT and M10 x 1. These match the standard bleeder port threads on grease gun heads worldwide. BSPT is standard on STAR guns and most UK, Australian and Asian equipment. NPT is the North American standard. M10 x 1 appears on European-made guns. The valve threads directly into the existing bleeder port or plug port on the gun head. Specify your thread when ordering.

How do I install an air release valve on my grease gun?

Unscrew the existing head plug or worn bleeder valve from your grease gun head, then thread the S-ARV into the same port by hand until snug. No special tools required for installation; hand-tight plus a quarter turn with a spanner is sufficient. The tapered thread creates a seal without PTFE tape under normal conditions. If your gun does not have a visible bleeder port, check the head for a small hex plug opposite the outlet; this is the bleeder port on most designs. The S-ARV is a direct drop-in replacement that takes under 30 seconds to install.

Can I add an air release valve to a grease gun that does not have one?

Yes, most grease guns have a threaded port on the head that is either fitted with a simple plug or left open with a set screw. The S-ARV threads directly into this port, converting any standard grease gun into a bleeder-equipped gun without drilling or modification. Check your gun head for a small threaded hole (typically 1/8" BSPT or NPT) on the top or side of the head, opposite the grease outlet. If a plug is present, remove it and thread in the S-ARV. If no port exists (rare on professional-grade guns), the gun cannot be retrofitted.

How do I use the manual air release valve to bleed my grease gun?

After loading a new cartridge or bulk-filling, press and hold the S-ARV/M button down, then pump the lever 3-5 times until grease (not air) appears at the valve port. Release the button immediately when grease appears; this seals the port and stops grease waste. The gun is now primed and ready to dispense. If air persists after 5 pumps, the air pocket may be large (common after bulk loading); continue pumping with the button held until solid grease flows. Cap the coupler end during bleeding to direct all flow through the bleeder port.

Why does air get trapped in my grease gun after changing cartridges?

Air enters the barrel in the gap between the old cartridge removal and new cartridge insertion. When you unscrew the barrel from the head, the pump chamber is exposed to atmosphere. When the new cartridge is inserted and the barrel reattached, a pocket of air sits between the cartridge nose and the pump chamber. This air compresses on each lever stroke instead of pushing grease forward. The faster you perform the cartridge change, the less air enters; but some air ingress is unavoidable without a sealed loading system. The S-ARV eliminates the problem regardless of how much air enters.

How do I fix a grease gun that stops pumping with grease still in it?

A grease gun that has grease in the barrel but delivers nothing at the coupler is almost always air-locked. If your gun has an S-ARV/M: press the button and pump until grease flows from the valve, then release. If your gun has no bleeder valve: disconnect the coupler, point the extension downward, and pump until grease flows (this forces air out through the outlet path, which is slower). If neither method works, the non-return valve in the head may be stuck open (preventing pressure build-up) or the follower seal may have lost contact with the grease column. Inspect both if bleeding does not resolve the issue.

How do I clean a clogged air release valve?

Remove the valve from the gun head, soak in mineral spirits or degreaser for 15-30 minutes, then use compressed air or a thin wire to clear the vent port. Grease can accumulate in the valve port over time, especially on the automatic version where small amounts of grease pass through during normal operation. After cleaning, test by blowing through the valve (air should pass freely on the manual version when the button is pressed; on the automatic version, air should pass freely at low pressure). Reinstall and test with a pump stroke. Clean annually or whenever priming becomes sluggish.

Does cold weather cause more air lock problems in grease guns?

Yes, cold temperatures increase grease viscosity, which makes air locks harder to clear through normal pumping. Thick cold grease moves slowly past air pockets, meaning more pump strokes are needed to push air through the system without a bleeder valve. The S-ARV solves this because it vents air directly from the head regardless of grease viscosity. In cold-weather service (below 0 C), the automatic S-ARV/A is particularly valuable because it continuously vents air without requiring the operator to remove gloves and press a small button.

Does the air release valve need regular maintenance?

Minimal maintenance is required: clean the valve port annually and check that the seal functions correctly. For the manual S-ARV/M, press the button periodically to confirm it moves freely and springs back to sealed position. For the automatic S-ARV/A, verify that air passes through when you blow gently (indicating the mechanism is not stuck closed with dried grease). If the valve leaks grease during normal pumping (when it should be sealed), the internal seal is worn and the valve should be replaced. Replacement is inexpensive and takes 30 seconds.

Is an automatic air release valve worth the upgrade from manual?

The automatic S-ARV/A is worth the upgrade in high-reload environments where operators change cartridges multiple times per shift. Fleet depots servicing 10+ vehicles daily, agricultural contractors greasing multiple machines per round, and construction crews with frequent cartridge changes all benefit from eliminating the manual bleeding step entirely. For workshops where cartridge changes happen once or twice per day, the manual S-ARV/M is sufficient and gives the operator more control over grease waste during bleeding. The automatic version is factory-fitted on the STAR S-706A V-Series for this reason.

Are the S-ARV valves compatible with all grease guns?

The S-ARV fits any grease gun head with a standard 1/8" BSPT, 1/8" NPT or M10 x 1 threaded bleeder port. This covers the full STAR range (S-701 through S-741), plus most professional-grade lever action and pistol grip guns from other manufacturers that use these standard thread sizes. The valve is not compatible with guns that have proprietary non-standard bleeder port threads (rare on professional equipment) or guns with no bleeder port at all (typically entry-level consumer models). Check your gun head for a threaded port before ordering.