Bad PBU in Kohler K-304-K

Is there anyway that a bad PBU or Mixer Cap could have been causing hot water to run out of the cold side of another faucet in the same bathroom?

I recently replaced the Pressure Balancing Unit and Mixer Cap in my Kohler k-304-k to solve a problem with inconsistent water temperatures. The new parts completely solved my problem with the shower but they also seem to have solved another problem I'd been having with the sink faucets in the same bathroom. Hot water would run out of the cold side for 30 sec or so before running cold.

More info if needed:

All the plumbing in this upstairs bath was installed about 10 years ago and worked great up until a couple years ago when the cold side of the faucets started running hot for the first 30 sec or so before they would run cold. It did this in the winter and summer and I saw no patterns in usage like it only happening after running hot water somewhere else in the house. It was pretty much always hot for 30 sec or so before it ran cold. We started noticing the inconsistant shower temperatures a few months ago.
Thanks!

That is possible. The pressure balance unit has a cylinder that moves/slides when the pressure changes on either the hot or cold side thereby balancing the pressure coming out of the fixture. If that seal between the hot and cold fails, water can pass through the PBU even when the fixture is closed.
There maybe another underlying problem that is causing the hot to flow into the cold through the defective PBU.

Do you have a recirculating hot water system?
What type of plumbing system do you have ?

Mr_David said:

That is possible. The pressure balance unit has a cylinder that moves/slides when the pressure changes on either the hot or cold side thereby balancing the pressure coming out of the fixture. If that seal between the hot and cold fails, water can pass through the PBU even when the fixture is closed.
There maybe another underlying problem that is causing the hot to flow into the cold through the defective PBU.

Do you have a recirculating hot water system?
What type of plumbing system do you have ?

Click to expand...

I don't have a recirculating system just a tank water heater in the basement. The bath in question is on the second floor.

Mr_David said:

That is possible. The pressure balance unit has a cylinder that moves/slides when the pressure changes on either the hot or cold side thereby balancing the pressure coming out of the fixture. If that seal between the hot and cold fails, water can pass through the PBU even when the fixture is closed.
There maybe another underlying problem that is causing the hot to flow into the cold through the defective PBU.

Do you have a recirculating hot water system?
What type of plumbing system do you have ?

Click to expand...

Thank you for the reply. I don't have a recirculating system. I have a tank water heater in the basement and the bath in question is on the second floor. My city does not use check valves and I don't have an expansion tank.