Recently replaced the mixer cap (Kohler GP77886) and regulator (GP500520 PBU)because of a leakey faucet. Parts were received for the Coralais Kohler faucet, installed and now the water will not shut off. I reinstalled the old parts with new "O" rings and again , the water will not shut off. I inspected the brass body and found nothing cloging the water supply. I made sure the regulator was seated properly prior to installing the mixer cap and stem. The replacement parts are identical to the original parts with the exception of the flanged collar. The new mixer cap comes with a flat collar. I have interchanged parts of the new and old along with interchanging the "O" rings. Nothing I have tried has worked. The water will not shut off at the shower stem. The before and after water pressure seem to be the same. Does anyone have a solution?

I see this post is from 2011. Well, I'm dealing with the same issue now. I will add that the new parts (as you have them listed) are different in two ways. The PBU is now the female connection in this unit, where as it was the male with my old parts. Also, curiously missing, are two spring caps which my old parts had but the new ones do not. I have been searching for am answer for over a week now (I can't see dishing out more dollars to a plumber when I already have over $120 invested in this damn faucet). If you have come across an answer since your 2011 post, please share.

Thank you.