Return Pump Clicking?

[dan]

I shut off my return pump for the last feeding of the day, when I plugged the sucker back in it started making a crazy clicking noise and the water is only getting halfway up the return line continuously changing levels up and down.
I shut it off, removed the hose clamp and fitting, cleaned it replaced the parts and the put the pump in the sump. It works when it's not connected to my return line, when I connect the two the clicking starts. Any ideas?
Lifeguard 1200
40gal cube
Small sump maybe 10-15g
The pump is directly under the tank.

I tried emptying the sump to lower the waterline but it still won't work. As of right now I just have a power head moving things around.

 

[AdInfinitum]

Not directly familiar with that brand but...First guess would be a bad impeller or broken impeller shaft. When you had it apart to clean did you pull the impeller shaft right out (assuming it's not one piece with this pump)? It could be broken in the middle inside the impeller. Also the impeller head could be separated from The magnet so it spins but then slips when under load.

 

[dan]

I did not pull out the impeller. I did start the pump in the sump with no connections. It worked and spewed water everywhere, so as it was running I pushed the return line on and it worked, well it's working until I can get a new one later today. Everybody still looks happy so far :/

 

[heath]

maybe an air lock...but its good that's its working...

 

[Pipes]

If you have a check valve on the return line check that too. It could be the flapper in the check. I've seen them ripped apart on a sump pump and making a similar noise.