Lubricate it
Open the pump again and give the inside of a really good slathering with SeaLube, which is a thick teflon grease. Once should keep your head working smoothly and quietly all season. Fall is the ideal time to do it, because the teflon grease protects the seals and other rubber parts from winter cold and drying out.Lubrication does more than just keep the toilet quiet. That squealing is the sound of the rubber seals and o-rings rubbing against the cylinder, and the effect is about the same as rubbing a pencil eraser against it...the rubber wears down. Lubrication prevents the seals from wearing and extends the time between rebuilds. However, nothing that's just poured down the toilet provides much protection...they're thin, and wash out in just a few flushes.