Medo pump repair/maintenance

[Charlutz]

I’ve got a Medo LA-45B. I’ve had it for years and it runs when I plug it in, but in a few minutes it starts rattling and not pumping. I’ve never repaired but I assume it’s a bladder or piston assembly. Trying to narrow it down. Anyone with experience would be helpful. Thanks!

 

[AquaStudent]

I have never had one of these pumps or had to repair one but I’m interested in electronics repair. Have you taken the case off to look inside? That would be my first step and may help narrow it down.

Since it’s working at first then goes off balance, what you’re thinking sounds reasonable to me. Was there an event that happened right before it started malfunctioning?

 

[Charlutz]

Taking it apart is the next step. I recall the pump having the same problem some years back just before I shut down my fish room. I took it apart then and couldn’t identify anything amiss so didn’t repair it immediately, then the fish room shut down making the pump repair a non-priority. I’m cleaning the room and hopefully going to set up a tank or few, so wanted to check out the equipment. I’m also in the market for a motor for an AC110 lol. I’ll take it apart and post back here once I have a solution.

 

[Grundsau]

Have you ever changed or cleaned the filter on top?

 

[Charlutz]

My recollection is fuzzy as it’s been years since the pump was running my tanks, but I believe that was the first thing I checked. It certainly would be the cheapest fix. Based on sound only, it seems to be more of a mechanical issue, but I’ll look at the filter too when I take it apart, hopefully I’ll find some time this weekend. Thanks!

 

[Charlutz]

Took it apart and it definitely needs a gasket/O ring. Issue is I can’t find the O ring without a rebuilt kit including the piston for $80. I have an email into a vendor to see if the gaskets are available without the piston.

 

[AquaStudent]

Do you have a set of calipers on hand? I have replaced o-rings using some of the industrial supplies shops like McMaster-Carr and theO-ringStore. Those are definitely designed for more bulk purchases but it would be much less than $80 (and if you need to get a few different kinds to get the exact right fit, you can order a variety).
Post the dimensions here too...it's a longshot but maybe I have a one the right size for a few of the projects I've been working.
Another option I've been wanting to try is 3D printing O-rings using TPU. I have no idea how long it would last, or if it would work, but I'd really like to try.
I can't really tell but is there a split in the membrane in the last photo at about 6 o'clock? Can't quite tell what's going on there.

 

[Charlutz]

Here’s the response I got from a retail store.

“Medo does not offer the gaskets separately outside of the kit. Typically in the time frame that you need to replace the gaskets, the piston will also need to be replaced. There are Teflon seals on the piston assembly that wear and a spring that will loosen over time. Both of these can lead to airflow loss.”

Sounds reasonable and consistent with the fact that I can’t find anyplace that sells the gaskets separately. To answer your question question, the outside diameter is 2” but that gaskets aren’t flat. One side has some grooves, presumably to seat it in place. I’ll probably just suck it up and buy the rebuild kit. I’ll post back once I’m up and running again.

 

[Charlutz]

The rebuild kit arrived today and the gaskets were the problem. New gaskets were soft, pliable rubber and old ones were brittle and cracked. Not sure if the piston needed replacing as, aside from cosmetic signs of age, the old one seemed just as functional as the new one. I replaced the gaskets and filter, put in the new piston and hooked it up. Pump has been running for three hours without issue. I think I could’ve replaced the gaskets and filter (if I could find the right sized gaskets) and saved myself the cost of the rebuild kit. Netting the $20 it would’ve cost me to buy the filter and estimate for gaskets, I’ll call this $60 spent in tuition for an education on how the pump works and I’m ok with that. Hopefully I’m good for a few years and this thread will be a reminder next time of what to try when the gaskets wear out again. Thanks everyone for the help!