filter help?!?

I have an emperor 400 that came (used) with a tank I bought last weekend. It seemed to make a grinding noise so we replaced the impeller thinking that could be the problem. The unit is clean and assembled properly. Any other ideas? My husband is an engineer, so I thought for sure he could figure it out :thud: LOL!! The part that is in the tank seems like it is not strong enough to pull enough water into the filter. It is adjusted so that it is running right now, and is quiet, but the water is only trickling out of the top, but the biowheels are moving. Will this be sufficient enough to function, or am I not getting enough water turnover (gallons per hour or whatever?)

yeah, we've really tinkered with the more obvious stuff, not sure what else to try. I guess I didn't really pay for it, so I'm not out too much if I can't get it working right, but I really hoped it would

the tank was about 6 or so inches shy of being filled all the way and although it was still fully submerged in water it now seems to be working a little better. When I did a search about this there were a couple of suggestions to just let it run for a day or two. I think I'll try that since its not making the noise any longer. Maybe I was just overly worried b/c I knew it was a used filter!
Later this week we'll be trying to set up the magnum 350 with biowheels I think the fun has just begun