I've got an '88 320i coupe which i just got a few days ago. I got it from a dealer and during the test drive i noticed that the right side and floor of the passanger footwell (left side of car as mine is right hand drive) was a little damp. I didn't pay atention to it as i thought someone must have just had wet shoes. Then i went back to test it the next day and it was even wetter. Anyways, the dealer said he'd fix it before selling me th car (we assumed it was just some rain water comming through the firewall).
However, i had to unscrew the cap off my expansion tank tonight with the engine still hot, as the pressure started to build up when i was unscrewing it, i just saw a whole heap of water gush down the side of the car just behind the front wheel, passanger side. And sure enough, it became wet inside the passanger footwell. I had a look with a torch and it seems that the heating pipes go around that area behind the dashboard so could one of them be leaking? and if so, why doesn't it leak constantly when driving, surely that's when the highest pressure occurs. I'm really in need of some idea, at least how to stop it temporarily if anyone knows what this is or it has happened to them as i've got puddles in my car at the moment. Thanks heaps in advance!