Momcozy M5 Not Suctioning? I Fixed Mine Fast

You sit down to pump—and nothing. No pull. No milk. Just frustration.

If your Momcozy M5 isn’t suctioning, take a deep breath. You’re not alone. And yes—it’s fixable.

I’ve been there. One day it worked fine. The next? My pump felt like it gave up. No warning. No error message. Just weak suction and wasted time. I almost gave up on it.

But after digging around (and scrolling way too many forums), I figured it out. I’ve helped other moms fix theirs, too.

In this guide, I’ll show you:

• Why your Momcozy M5 might stop suctioning
• How to fix it step by step
• What to do if nothing works

Let’s get your pump—and your peace of mind—back on track.

Quick Diagnosis — What Suction Issues Feel Like

How can you tell if your Momcozy M5 isn’t suctioning right—or just having an off day?

Here’s what happened with mine when it started acting up:

• The pull felt super weak. Almost like it wasn’t even trying.
• No milk was collecting, even though I knew I wasn’t empty.
• I heard a faint hissing sound from one side.
• And sometimes, the rhythm just felt… off. Like it had changed overnight.

If that sounds familiar, you’re likely dealing with low suction—or no suction at all.

And yes, there’s a difference.

Low suction feels like the pump is barely doing anything. You might get a little milk, but it’s slow and frustrating.

No suction means the pump is running, but it’s not pulling. At all.

The good news? It’s usually nothing serious.

Most of the time, it’s an easy fix. And we’ll walk through those next.

10 Common Reasons Your Momcozy M5 Isn’t Suctioning

If your Momcozy M5 isn’t suctioning, it’s likely one of these reasons. I’ve dealt with every single one—or heard them from other pumping moms.

1. Parts Not Assembled Right

This is the top reason—by far.
Even one piece out of place can kill suction. Make sure everything clicks in snug, especially the duckbill valve and top cover.

2. Duckbill Valve Is Torn or Loose

If suction feels weak, check the duckbill.
A tiny tear or stretched tip can break the seal. If it doesn’t snap shut on its own, replace it. (I swap mine every 1–2 months.)

3. Flange Doesn’t Fit Well

Too big, too small, or not centered = bad suction.
Your flange should sit flush on your breast with your nipple centered. If it feels off or leaky, it probably is.

4. Air Vents Are Blocked

The M5 has small vents near the collection cup.
Moisture or milk can clog them, especially if you store parts while damp. Wipe them dry and check they’re clear.

5. Membrane Is Worn or Missing

This little silicone piece is easy to miss—but it’s key.
No membrane means no suction. If it’s stretched or torn, it won’t work right. Check that it’s snug and smooth.

6. Motor Is Weak or Fading

If everything’s clean and connected but still weak, the motor could be dying.
Mine got loud before it stopped working. If yours is under warranty, contact Momcozy support.

7. Milk Collector Is Too Full

I’ve made this mistake—trying to squeeze in one more session.
Once it’s too full, suction drops fast. Empty it between sides if needed.

8. Wrong Mode or Suction Level

Sometimes I bump a button by accident.
Make sure you’re in expression mode, not massage. If it feels weird, reset it.

9. Battery Is Low

Low battery = weak suction.
Even if the light is on, the power may dip. Try a full charge or plug it in mid-session.

10. Moisture Inside the Pump

Steam, spills, or too much washing can let water in.
Let it dry fully before you reassemble. Never use it damp—it can mess with the motor.

Step-by-Step Troubleshooting Guide

Okay—if your M5 isn’t suctioning, this quick checklist usually fixes it. I run through it anytime mine acts up. It takes 3–5 minutes, tops.

Quick Fix Checklist:

1. Take it apart completely.

Lay every part on a clean towel. Look for damage, grime, or anything missing.

2. Check the duckbill valve.

Pinch and let go. If it doesn’t snap shut, swap it out.

3. Look at the membrane.

It should be smooth and springy. If it’s loose or cracked, replace it.

4. Clean and dry everything.

Even a drop of water can mess with suction. Dry all parts well, especially the air vents.

5. Reassemble carefully.

Click every part into place. Make sure the motor and cup are aligned right.

6. Reset the mode.

Hold the power button to clear any weird settings.

7. Test one side first.

Use just one cup to check suction. It’s easier to feel what’s happening.

8. Plug it in.

If your battery’s low, charge it or use while plugged in.

9. Try again.

If suction feels stronger now, great! If not, you might need to replace a part—or reach out for help.

Flange Fit Problems — The Hidden Cause of Suction Loss

Flange fit can make or break your session. Too big, too small, or off-center? That’s enough to ruin suction or cause leaks.

I didn’t notice my size was wrong at first. It looked fine—but I was always adjusting it. My output dropped. Turns out I needed a smaller insert.

Why Flange Fit Matters

If the flange doesn’t seal well against your skin, air sneaks in. That breaks the vacuum—and poof—no suction. You might feel pinching or rubbing. Or you’ll see milk pool instead of flow.

How to Measure Nipple Size

Here’s the method that worked for me:

• Gently measure your nipple (not areola) in millimeters—right after a warm shower or pump session.
• Add 1–3mm to find your best flange size.
• Don’t guess based on your current flange. Go by the numbers.

Want a no-guess method? Try a printable flange size guide. Print, cut, and measure—it’s easy.

My Favorite Inserts

I love silicone flange inserts, especially if you’re between sizes. Here are some popular options moms (and I) recommend:

• 17mm — for narrow nipples
• 19mm and 21mm — for a snug but comfy seal
• Combo kits — with duckbill + insert (great if you’re replacing both)

You can find these on Amazon or Target in the U.S.—and buying multipacks usually saves money.

When to Replace M5 Pump Parts

Pump parts don’t last forever. They stretch, tear, or just wear out—and that means less suction.

Here’s a quick chart I keep taped inside my pump bag:

Pump Part	Replace Every	Signs It’s Time
Duckbill Valve	Every 1–2 months	Not snapping shut, feels loose
Flange/Insert	Every 2–3 months	Cracking, warping, discomfort
Membrane	Every 1–2 months	Torn edges, suction loss
Collection Cup	Every 3–6 months	Cloudy, stained, or leaking
Motor (Pump Unit)	As needed (warranty)	Weak pull, loud noise, no suction

What to Do If Your M5 Still Isn’t Working

Tried everything and still no suction? Don’t panic.
Sometimes the issue is rare—or the part is faulty.

Contact Momcozy Support

Go to the Momcozy support page. They replied within 24–48 hours when I contacted them.

What to Send

Have this info ready:

• Your order number or receipt
• A clear photo of your full pump setup
• A short video showing the suction problem
• The pump’s serial number (usually under the motor)

That makes it easier for them to help—or send a new part fast.

Pro Tip: Take Photos Early

Snap a few pictures or take a quick video before reaching out.
It’ll save time and help explain the issue better.

If your pump is under the 1-year U.S. warranty, they’ll usually offer a free replacement.

Final Thoughts — Don’t Panic, Just Reset

I know how frustrating it is when your M5 stops suctioning—especially when your baby’s crying and you’re on a tight clock.

But most of the time? It’s something small. A loose valve. A wet part. A flange that’s just a little off.

Give your pump a reset. Run through the checklist. Swap out tired parts.

Still stuck? Reach out. You’re not alone—and help is there if you need it.

Want to compare the Momcozy M5 vs M9? Or figure out your perfect flange fit? I’ve tested both—and I’ve got more tips to share.

Grab my free troubleshooting checklist or sign up for more real-life, mom-tested pumping help. 

Frequently Asked Questions: Momcozy M5 Not Suctioning