What year is the car? If it is a 97/98 then the fctory hose clamp that goes to the unit isn't long enough to tighten ALL the way down, check if the clamp is tightened and then try to turn the unit, if it moves you have to get a universal clamp that will tighten that far.
Also when you removed the electronics did you make sure the rubber o ring came out with the electronics? If it remained stuck in the factory housing then that is your problem.