Ok here is what I have going on. I have a 1999 Diamante that is leaking like a sive on the drivers side. It is not coolant as it does not smell like it. Where I am getting the water is in the footwell. when I say water I mean up to 4 inches after a hard rain (I live in Washington). Now I do have to replace a seal on the drivers side door which I hope will cure this but the oddest thing is that I had a semi water proof car cover on the car and bang 3 inches of water in the fooot well as well as a wet carpet under the seat and behind the seat. Can anyone tell me other areas to look besides the obious worn seal. Last thing I want is to replace the seal still get a leak.

 

Have you found anything out on this yet? I have a 2002 Diamante and it has leaked there on the drivers side for a couple years though not nearly as bad as you are talking about. Does anyone know where this may be coming from?

 

Well I got the new door seal and $400 bucks later the leak is still there! Although it seems much smaller/ slower as it only dampens the carpet. I did notice another thing I did not before. The lower bolt for the dead pedal broke out of the firewall leaving a hole. I repaired it by putting a large screw in the the dead pedal and into the fire wall. I am wondering if this was the cause all along. When they replaced the seal they said they ran water over the car as a test and a-ok. I am wondering if there is water getting behind the firewall building up and into that hole. It looks like there is a space between the inside and outside firewalls. Other than that I am at a loss.

 

Funny I found this 13 years later, It's highly likely coming from your air conditioning. older Diamantes seem to have an issue from the air intake where it corrodes and allows water to flow through and out the back footwell.