help with dia-tom filter plz

i just bought a dia-tom filter

I had it set up in my 40 gal tank, i charged it up with a plastic pitcher, the water was running clr, then i put the outtake, and intakein the tank. about every 3 sec or so there is a fizz noise and I noticed a burst of what look like tiny bubbles.

are these bubbles or am i seeing dia-tom earth, with light reflected off of it?

I broke down the filter, washed everything into a 5 gal bucket, it still makes a fizz noise every few sec, i think i am getting air into the loop somehow and it it sucking air through the gasket making thousands of tiny bubbles, is this normal?

also the motor is running really hot, i know that it is air cooled but still this think wont burn you but it is very hot to the touch?

I had a hard time getting the impeller primed as well

are these things just junk????

usually you can find info on bad equipment, did i just get a lemon?

ok, I unpluged the dia-tom filter and let it sit for a few min, then it blew some of the diatom earth into the tank, i was definatly seeing small air bubbles, the diatom powder looked like milk in the water. I also found a card was in the box that siad that the filter motor ran at 145 F, lol thats why it felt so hot. I have let it run on my tank for about an hour and the water looks great.