I suspect that your new (old) pump was dirty inside and when you started using it it stired up the trash. You might get it cleaned out by flushing it out. Remove the return hose and block the canister outlet. Put the return hose into a container and fill the reservoir, and turn the wheels back and forth until you flush the system. It takes a little bit of fluid so have at least a couple of quarts before you start. If that doesn't correct the problem NAPA has a seal kit for $16 that has all of the O rings and a new front seal that you can use to repair your original pump.