Replaced a couple of brake lines and two wheel cylinders, and been bleeding the brakes and still don't have any brakes. Is my master cylinder gone? Not sure what to do now.
What does "no brakes" mean - no braking power at all? Less than what you had before R&R? Same as what you had before R&R?
When a brake line is replaced and a section of brake system is thus completely dry, when you start to bleed the brakes, initially the pedal will offer barely any or no resistance as the fluid fills the empty space in the brake lines. As you are continuing to bleed the brakes (correctly), the pedal will be gradually increasing in firmness as air is purged from the lines. If you haven't experienced this, either you didn't bleed correctly or you have another problem in the braking system.
Proper bleeding procedure:
This requires two people or a power bleeder to maintain pressure in the brake system. There are various "one man bleeder" systems sold in auto parts stores - I don't know whether they work as well as two people or a power bleeder.
Any time any bleeder is opened at all, brake system must be pressurized. This means either someone needs to have their foot on the brake or power bleeder must be applying positive pressure to the system.
Bleed from the furthest caliper from the master cylinder to the closest. Which one is furthest depends on the car and its brake line layout. Consult the car repair manual.
If the car has ABS, a specific procedure generally must be followed to bleed the ABS module. Consult the repair manual for the vehicle.
As pointed out, the master cylinder is supposed to be bench bled if it's replaced. You may be able to get away without doing so but it makes bleeding the entire system more time consuming.
Verify you see air bubbles during the bleeding process.
Verify air bubbles cease coming out when you think bleeding is finished. I do this by bleeding every corner again in the proper sequence when I think bleeding is done.