I recently discovered the driver's side floor was very wet in my 98 GS 300 with 108K miles.
I first had this problem 5 years ago after the evaporator core was replaced to fix an a/c problem (a very extensive and costly repair). The a/c radiator assembly was also damaged in the course of that repair and had to be replaced. Water under the carpets (both sides) shortly thereafter was due to the AC drain not being properly reseated into the external tube during that repair/replacement.
Now I have water under the driver's side carpet again. All the drains have been checked and are clear. The mechanic says the translucent AC drain is clear and does drain when the car runs. Leaning up under the dash, he thinks the leak is a slow drip he saw which appears to come from the heater box joint. The approximate $1600 cost of tearing out the dash to get to the heater box to fix the joint is excessive given the value of the car.
My questions -- is this a common problem? It seems an unusual coincidence to have both these issues with the heater box/evap core. I don't see many postings on the topic. Did the prior replacement of the evaporator core require splitting open the heater box? Is it likely or possible that the heater box joint/seal could have been damaged during the replacement of the evaporator core? What is the nature of the material sealing the heater box joint in this particular model? The mechanic tried sticking some butyl tape on the small part of the joint he could reach (without removing the dash) but that didn't stop the leak.
What should I do? Are there any other possible causes or fixes for this problem? Has anyone else had this experience?
