I recently replaced the head gasket on a 3rd gen Prius. Water has leaked below the dash inside the car. I'm guessing this means I should have put RTV sealant on the trim piece that connects to the base of the windshield.
You sure it’s not the AC system drain? I’ve removed the windshield wiper cowling many times and never had a leak internally. Might just be a coincidence.
During the disassembly did you happen to have difficulty removing the heater hoses? What you may have done is compromised the heater core. Another possibility/coincidence is the evaporator housing drain might be plugged allowing for water build up and subsequent leaking.
I don't think I damaged the heater hoses or heater core but if this turns out to be coolant, I will check more in that neighborhood. I have a vague memory of a drain line that I thought was a coolant reservoir overflow tube so maybe that relates to a.c. condensation. Where is the condensation line located?
The evaporator drain is under the glove box in the extreme L/corner by the console and exits out to the undercarriage. You’ll have to pull back the carpet to get unrestricted access. If the carpet is saturated in this area there is a very high probability this is your problem.
