Chrysler Repair: Air in Brake Lines, dodge grand caravan, grand caravan

Question
We have a 2002 Dodge Grand Caravan.  My brake pedal became spongy and had to push it down to the floor before it would slow down.  My mechanic found air in the brake lines.  He bled the brakes and found no evidence of leaking fluid.  It was fine for one week, then the same problem came back.  Again air in the brake lines, they replaced the master cylinder.  It was fine for about 2 weeks then the problem came back.  This time they found air in the front left brake.  They bled the brakes again and replaced the caliper.  About two weeks later the problem came back again.  Any advice on how to deal with this or what the problem really is.  Thanks for your help.

Answer
Hi David,
Do you have anti-lock brakes system (abs)? If so that system has to be bled after the regular system is bled, and following a procedure that involves the use of the Chrysler diagnostic readout box, according to my '02 minivan manual.
If you don't have abs then all I can suggest is that whoever is doing the bleeding is not doing it properly. You have to really open the bleeders and drive alot fluid through the system to properly get the air out. I can xerox copy and mail you the pages about bleeding the basic system, but the abs bleed will require the diagnostic box.
I would suspect that you may have a caliper or wheel cylinder that beginning to leak would be another possible explanation. Are you loosing brake fluid to any extent?
Roland