Presuming there is no crack in the casing and you aren't overfilling the tank, I would suggest one possiblity, as it's the only reason any of my Eclipse's have ever done the same thing.

First, make sure the powerhead is firmly in place. If it's loose, it might be tilted back and if so, would send the water backwards. Also check the rubber pad the powerhead sits on. Is unseated?

The small shoulders on the sides of that pad are what channels the water into the media basket, so if it's off kilter, it will allow the water to flow back to the left of the powerhead.

However, if the powerhead is firmly in place and the pad is properly seated but degraded and no longer holding the channeling shoulders up, it's time to replace the pad.

But if that proves the case, I honestly don't know where you can buy only the pad without the entire moror assembly. You could try going directly to Marineland.

Good luck.

I have the Eclipse II and haven't used the pad birdwidow is talking about for several years and it only leaks back into the tank a tiny bit from that area. When mine has done as you described it is because I needed to clean out the biowheel chamber (not the wheel itself, but the gunk that builds up in the biowheel chamber and the water outlet into the tank.) The water level flowing across the filter would get too high because the pump was pulling in more than it could despell and the water would migrate to the edges of the hood and leak over the side in the area where the heater accessory goes. Cleaning the filtering area alway stopped it for me.

debndal:

You are correct. Excess debris would do it too. I also tried it without the pad, and it leaked. Not much, but as the tank sat on furniture, even just a little was still to much for me.

I just wanted to stop by and say Thanks! I had apparently lost the rubber pad under the powerhead at some point in time. We put a couple pieces of tubing under it and that has made it amazingly quieter! Cleaned up all the leak streaks and did a thorough cleaning; it seems to be helping so far!

Youe are welcome, and I was wrong about replacing that rubber pad.

One of the nicest things about Marineland, is their after-market customer service and, it turns out- replacement parts for every product they make, directly from the mfg.

If you get tired of little pieces of tubes, you can order a replacement pad for less than $4.00 directly from Marineland. I didn't check shipping, but doubt it would be much.

See: https://www.marineland.com/store/Flexible-Motor-Mount-for-PFE1-PFE2-PFE3-P333C0.aspx

I did have to order the rubber pad, it started leaking again already. $9 shipping on a $3 part! Outrageous! Well, at least I was able to order just the part I needed instead of a whole new hood. Again, thank you! :D