Air in brake-line - help!

So, my brakes failed on me on Saturday. Towed it to a shop where they replaced the master cylinder which was shot as well as the rotors and pads on the front brakes (fine, the van has 160,000+ miles). They were about to give it back to me, but then said "we have to re-bleed the brakes, there still seems to be air in there." So they bled them a second time and I drove it home fine, brakes all good.

But over the course of the next 48 hours, the pedal became squishier and squishier until it was back to being really dangerous. So I took it BACK, they bled the brakes a THIRD time and test drove it for miles and miles. Then I drove it home yesterday evening and the brakes were nice and tight-braked right away. But this morning...it seems to be getting squishier again. It takes about half the brake pedal to do anything.

Is there some way that air could be getting back in there again? Like maybe they're bleeding the brakes properly but over the course of hours, something lets air back in again? Is there anywhere on a brake system that could do that? Has this ever happened to anyone else? I don't know what to ask the mechanic... Help! Thanks!

You have a leak somewhere, period.
Check the front brake hoses, check the cylinders in the rear, they leak all the time. Check the connections where there is a nut and flared fitting, they get brittle and break easily when moved around during master cylinder installation.
Check where the brake line connects to hoses in the rear, sometimes the factory weld is defective.

If there's no leak, you have to wonder if they bled the master cylinder correctly before they installed it. It can be done on the car with a kit but, is usually done on a bench before it's installed. Here's is an explanation http://www.fd3s.net/master_cylinder_install.html: Scroll towards the bottom.

http://www.howstuffworks.com/master-brake1.htm

Aw geez, how I wish I were a mechanic myself so this wasn't all so traumatizing.

Thank you very much, I'll let you know what it was when it gets fixed...

Aw geez, how I wish I were a mechanic myself so this wasn't all so traumatizing.

Thank you very much, I'll let you know what it was when it gets fixed...

As they say a Home Depot "You can do it, we can help". This past year I put in a: new master cylinder, ABS modulator and new rear wheel cylinders. I spent months reading books and this forum was a big help! The 95 van works like a champ now.

Try getting a couple books and read them. It takes time, but its kind of fun as well.

Soooo, apparently it was a faulty master cylinder. Had a hairline fracture...

Thanks for your help!

A prime example of new parts being bad. A lesson for all. Thanks for posting the fix. Cheers