Air in brake lines..
 

Yesterday my brakes started feeling squishy and my brake warning light came on. When I got home, I saw that the fluid in my master cylinder was really low, so I filled it back up. When I drove it again, the brake light went away, but the pedal still feels soft. I know the procedure to bleed the brakes (RR, LR, RF, LF), but I've also heard you need to bleed the master cylinder. Is this necessary, and if so, how do you do it? Also, I've heard I could have gotten air into the ABS system and would need to take it to a shop with Tech II to bleed it. Any ideas or suggestions?
Thanks

Bleeding the master, to my knowledge, is not necessary unless it is a new MC. This is done on a bench, with it out of the truck, and essentially moves the piston (not sure if that is what it is actually referred to as) and removes air from the MC itself. There are kits for this, usually sold by brake manufacturers like SSBC when you buy a kit. I have never noticed anything at, say, Kragen. I dont believe it is normal bleeding procedure, I have never seen anyone yank a functioning MC that was properly bled prior to install, to do it over again. Not sure on the ABS question, to me bleeding brakes is bleeding brakes, I never worried about anything else than the standard operating procedure.

I say bleed them as normal and see what you have. If you still experience problems then go from there. Only other thing I can think of after that is a bad MC.

Use a power brake bleeder. Motul has a nice one that pressure bleeds the brakes from the master.

just go get a nice set of four one way bleeders, tubing to fit them and four coffee cans. i went through this with my bronco [rear abs] tried the farthest from the master theory did'nt work, finally did them all at once, bleed two big bottles through, solved all my issues.

fluid is low again
 

Thanks for the replies guys, but it looks like I'll need to fix something else first. I was planning on trying to bleed the brakes tonight, but on my way to work this morning, the brake warning light came on again. When I got to work I popped the hood and saw that the fluid was low in the master cylinder again. I guess this means i have a leak somewhere? Where should I start looking or is there something else I should check first? Thanks.