97 voyager
 

i have a 97 voyager that keeps getting air in the rear brakes... not sure
why? There is no leak that i can see... (the only place that i cant see is
directly over the gas tank, but there seems to be no fluid loss, if there
is, its negligible over a few months) What happens is all of a sudden the
brakes start to get spongy, and the i lose almost all the pedal. Then i
bleed the rear brakes and everything is fine for months. How in the hell
is the air getting in there? Someone told me that it might be the brake
booster, but why just the rear brakes, and is there any way to test for
that?