Kohler Shower dripping

[Mpt1123]

Here's an odd one for everyone. I have a Kohler Rite-Temp shower faucet that periodically will not get hot enough. It gets hot, just not enough for a comfortable shower. I've done this several times and here's the process. I replace the valve and the plastic diverter. This does not fix the problem right away. A few days later the water gets hot again and the problem goes away for about a year. I would have bet on defective parts but I've done this 3 times now, so something else is causing the problem. Now for something new. When my wife fills the washing machine on the first floor, the shower (on the second floor) starts to drip water. Very weird. I am on well water with a constant pressure system that was installed two years ago. The only thing I can think of is that the pressure system is somehow forcing water through the shower valve and it's triggered by the need for water for the washing machine. Any thoughts or ideas are greatly appreciated.
Thanks.

 

[Smooky]

Have you cleaned the valve body as suggested here?
http://helptopics.us.kohler.com/link/portal/5641/5712/Article/2303/K-304-Rite-Temp-Valve-Cleaning
After cleaning the valve and before installing the PBU and cartridge, I would turn on the water to blow out any debris that might be in the water lines. If you clean it out good, blow the lines out, then replace the cartridge and pressure balance unit you should be good to go.

 

[Sponsor]

 

[Mpt1123]

Thanks, I'll give that a try and let you know.

 

[Mpt1123]

I took the faucet apart and there is no aspirator in the valve body, so there's nothing to clean. As for the dripping from the shower head, it turns out that when I originally installed the faucet years ago the instructions said not to use any spacers when mounting the mixing cap to to the valve body. The instructions with the new mixing cap says to use 1 spacer. When I reinstalled it after checking for the aspirator, I removed the spacer, tested the shower by filling the washing machine and .... no dripping. I suspect that the spacer provided just enough of a gap to allow the water pressure from the constant pressure system to pass the o-rings in the mixing cap and out of the shower head.