Key Takeaways
- Properly priming the M12 grease gun prevents air locks and ensures consistent flow, avoiding tool damage and frustrating project downtime.
- If automatic trigger-based priming fails, a manual method using the bleed valve and rod lock provides a reliable secondary fix.
- Users should always purge the gun before first use to eliminate factory-test grease and prevent potential lubricant cross-contamination.
- The cordless M12 model delivers a powerful 8,000 PSI and can dispense up to seven grease cartridges on one battery charge.
- GenuineTools provides authentic Milwaukee power tools and grease guns at significant discounts of up to 60 percent off MSRP.
Priming Your M12 Milwaukee® Grease Gun: What You Need To Know
To prime the Milwaukee M12 (2446-20) grease gun, point the hose in a safe direction and pull the trigger several times until a consistent bead of grease flows from the coupler. This "automatic" method removes air pockets from the 8,000 PSI pump to prevent seal damage and ensure reliable lubrication. For first-time use, always purge the tool by dispensing grease into a rag to clear any residual factory-test lubricants.
If the trigger method fails, use the manual priming process by locking the follower rod into the plunger and pressing the side bleed valve. Slowly push the rod forward while holding the valve until grease appears, then disengage the rod and seat it fully into the cylinder. Properly priming your cordless gun allows it to dispense up to seven cartridges on a single M12 REDLITHIUM™ battery charge.
Authentic Professional Tools Up to 60% Off MSRP. Why Contractors & DIYers Choose GenuineTools!Get Milwaukee®, DeWALT®, Ring, etc tools at unbeatable prices. Highly rated by verified customers who trust authentic equipment. Why Choose GenuineTools:
30-Day Money-Back Guarantee: Full refund for defective or unopened items; opened items may be subject to a restocking fee. |
How to Prime the M12 Milwaukee® Grease Gun
Before you begin priming your Milwaukee® grease gun, be sure to have these materials ready:
- A charged M12 REDLITHIUM™ battery pack
- A loaded grease cartridge installed in the cylinder
- A clear, open area to point the hose safely
- A clean rag to catch any initial grease discharge
Then, follow these steps in order. Each one builds on the last, and skipping ahead is what causes most priming failures with this tool.
-
Insert the battery pack: Slide your M12 REDLITHIUM™ battery firmly into the battery port until it clicks into place. The gun won't operate without a secure connection, and a partially seated battery can cause inconsistent trigger response during priming. If you're using the tool for the first time, make sure the battery is fully charged before starting.
-
Point the hose away from your body: Hold the hose assembly by the spring strain relief (not the coupler tip) and point it away from your face, hands, and anyone nearby. When grease finally breaks through during priming, it can release with force due to the built-up air pressure inside the cylinder. This is especially important on first use.
-
Pull the trigger to start priming: With the hose pointed safely away, pull and hold the trigger, then release. Repeat this cycle several times, as grease typically begins flowing from the coupler within a few trigger cycles. Once you see a consistent bead of grease coming through, the gun is primed and ready.
- Purge the tool before first use: Before putting the M12 grease gun to work on any real lubrication job, dispense grease until the flow is clean using the exact grease you plan to use. To purge, simply prime the gun as described above and dispense grease into a rag or waste container until the flow is clean and consistent with no discoloration or mixed grease coming through. This takes less than a minute and protects your equipment from grease contamination right from the start.
Priming your 2446-20 will help it deliver reliable and consistent grease flow.
How to Manually Prime the M12 Milwaukee® Grease Gun
Manual priming kicks in when the automatic trigger method isn't moving the grease. This happens most often with a brand new cartridge, after the gun has been sitting unused for a while, or when air has gotten into the cylinder during a cartridge change. The process uses the rod and bleed valve system built into the gun.
Work through the following three steps carefully and in order. Rushing through any one of them is what causes the process to fail and forces you to start over.
-
Pull and lock the follower rod: Reach under the cylinder and pull the follower rod back firmly toward the rear of the gun. Once it's fully extended, rotate the rod handle 90 degrees to lock it into the plunger. This action engages the rod with the plunger so you can manually force the grease forward. If the rod won't pull back, press the bleeder valve to release built-up pressure inside the cylinder first, then try pulling the rod again.
-
Press the bleed valve while pushing the rod: With the rod locked into the plunger, use your thumb to press in the bleed valve located on the side of the pump body. While holding the valve in, use your other hand to push the rod slowly forward into the cylinder. Keep steady and even the pressure on both the valve and the rod, as jabbing or pushing too fast can create new air pockets rather than clearing the existing ones.
- Release the plunger once grease flows: Watch the coupler tip of the hose. The moment you see a consistent bead of grease appearing, rotate the rod handle back 90 degrees to release it from the plunger. Then push the rod completely into the cylinder to seat the plunger fully against the grease cartridge.
From here, the gun is manually primed and ready. Pull the trigger to confirm normal motor-driven flow before connecting to any grease fitting. If grease flows cleanly, you're good to go.
Troubleshooting Your M12 Milwaukee® Grease Gun
|
Problem |
Likely Cause |
Fix |
|
Unable to pull back rod |
Pressure build-up in cylinder |
Press the bleeder valve to release pressure, then retry |
|
Unable to push rod forward |
Rod is locked into plunger |
Rotate rod handle 90° to disengage from plunger |
|
No grease when trigger is pulled |
Empty cylinder or air pocket |
Check cartridge level; re-prime gun if air pocket suspected |
|
Grease flow is slow or inconsistent |
Air pockets in cylinder |
Manually prime using bleed valve and rod method |
|
Grease appears discolored on first use |
Factory test grease mixing with new grease |
Purge tool fully with your chosen grease before use |
Authentic Milwaukee® Grease Guns Are Available at GenuineTools
GenuineTools carries different Milwaukee® grease guns and other power tools.
If you're in the market for the Milwaukee® M12 Grease Gun or any other tool in the M12 lineup, GenuineTools stocks authentic Milwaukee® products up to 60% off MSRP for contractors and DIY enthusiasts who want the real thing. We also provide a 30-day money-back guarantee for all purchases.
From Milwaukee® grease guns to impact drivers, we carry the power tools you need to complement your existing Milwaukee® lineup.
GenuineTools has authentic Milwaukee® products that are priced very competitively.
Customers trust our authentic Milwaukee® selection and our transparent and affordable pricing. We also ensure that our customer service is personalized, so you’ll receive expert advice suited for your specific needs.
Shop Milwaukee® Grease Guns at GenuineTools →
Frequently Asked Questions (FAQs)
When should I prime my M12 Milwaukee® Grease Gun?
Prime the gun any time you install a new grease cartridge, when the gun has been sitting unused for an extended period, or when you pull the trigger and no grease comes out despite the cartridge being loaded.
Air pockets are the most common culprit, and priming clears them out so the pump can draw grease consistently through the hose and coupler.
How do I manually prime the M12 Milwaukee® Grease Gun?
Pull the follower rod back and rotate the handle 90 degrees to lock it into the plunger. Then press the bleed valve while slowly pushing the rod forward into the cylinder. Hold both until grease appears at the coupler tip, then rotate the rod handle back to release the plunger and push the rod fully in.
How many grease cartridges does the M12 Milwaukee® Grease Gun dispense per charge?
The Milwaukee® M12 Grease Gun dispenses up to 7 standard grease cartridges on a single M12 REDLITHIUM™ battery charge. That's more than enough capacity for a full day of routine maintenance work on most job sites, making it a highly practical cordless option for tradespeople who hate stopping to recharge mid-job.
Do I need to purge the M12 Milwaukee® Grease Gun before first use?
Yes. Milwaukee® recommends purging the gun with your intended grease brand before using it on any equipment. Every unit is factory-tested before it ships, which leaves a small amount of residual test grease inside the pump body, hose, and coupler. Dispensing into a rag until clean grease flows through eliminates any risk of cross-contamination with the lubricant you're actually using.
What Milwaukee® Grease Guns Are Available at GenuineTools?
GenuineTools carries the Milwaukee® M12 Model 2446-20 and various M18 models. All products are authentic Milwaukee® stock, not third-party replacements or grey market imports.
*Note: Pricing and/or product availability mentioned in this post are subject to change. Please check the GenuineTools website for current pricing and stock information before making a purchase.