The rear tire of our 1995 Honda Civic has a leak. In about a week, the
pressure goes from 30 psi to just about nothing. But I can't find the
leak.

The Honda dealer checked all 4 tires and declared that none leak. But
still, after a week, the rear tire is flat.

Today I checked it myself with soapy water. No bubbles. I removed the
wheel from the car and now it is in our bathtub upstairs and there are
STILL no bubbles.

How can this be? Any ideas?

R.