XP4 working...but not working! Really confused, please help!

by Dawn
(Scotland, UK.)

Hello

My less than 2 year old XP4 filter has been giving me some problems, and despite trawling through the FAQs, I can only find previous Qs that are half-similar to mine, and I feel I'm going round in circles and know less than when I started!

Anyway. The filter will run, and is maintaining water quality, but it is frequently making a rattling/spluttering noise. This is followed by the flow stopping completely, then resuming after some more dry sounding rattles. It almost sounds like it's air getting trapped then expelled. But I don't think that's what it actually is!

I can find no leaks. Everything fits true and flush, nothing is loose or coming loose and the impeller turns (with or without cover on). The rattling noise seems to be coming from the impeller though.

I read in another FAQ that if the impeller spins, I do not need a new motor. Is that correct? I also read that if the magnet is still strong, I do not need a new impeller. Is that correct? I thought it would be the impeller. I tested it on my fridge, and it practically flew out of my hand! As you can probably tell I'm really stuck and more than a little confused. I know I have it all set up and primed correctly, I've been using XPs for almost 7 years.

Incidentally, my original XP2 is still going strong with no replacement parts (touch wood)!

Thanks so much for any help.

A: The symptoms you describe point to either an air leak on the intake side (above the water line) or an aerator is discharging air bubbles too close to the filter intake causing air to enter the filter system that way. The problem is actually called "pump cavitation". My guess is that if you looked at the side of the filter you would see that the canister is not completely full of water and has air in the top. I would talk to someone locally about this or you can contact the manufacturer,
Mars Fishcare, directly.