No, the truck does not need to be running.
I have found that if the ABS fuse is removed, that will help.
Did you install the calipers on the correct sides?
The bleeding screws need to be up

 

Yes both the bleeding screws on the calipers are facing upwards

 

Well I say "nope" but I've never tried it.

You will be dealing with the extra pressure from the power brakes.

I guess the correct answer is, the experts do it with the engine turned off; so why would you think that would be a better way.

The vacuum method works well

Because when I tried to bleed them with the truck off the pedal kept going to the floor as soon as I started it. And it feels soft.

 

Find a gravel road and engage the ABS. I bet you need to burp it.

 

Could be a booster issue.
Could be a bulging brake line issue.
Could be an air pocket in the master cylinder.

How long ago did you change out the rubber lines?

 

Would I have to bench bleed the master cylinder then?
I haven't replaced any rubber lines yet but I am going to.
I didn't think it had abs but when I looked into it more I found out it did.

 

Would I have to bench bleed the master cylinder then?

Just unplug any connections and then unhook the brake lines. Put rags to catch the fluid so it doesn't eat your truck. Bench bleed it in place.

Try the ABS burp, first.

 

Try the ABS burp, first.

How would I do that?

 

Gravel road. Reasonable, safe speed. Slam on the brakes. Pedal should pulse as the truck tries to maintain consistent wheel speed on the variable surface. May hear a "grinding" noise as the ABS pump churns.

I am sure there is a way to trigger the pump with a jumper wire, but I don't know it.

 

Sometimes you have to keep working on it to get the air out of the ABS. Mine was a bit of a pain too.

 

By working on it, do you mean bleed the brakes a couple times?

 

Yes, that's what I had to do . I was a little impatient so I started driving while the pedal was still a little soft but the bubble worked it's way out within a week . Brakes are great now.

 

Well the engine is not running . the brake pedal is the down did the wood stick of the driver seat . take it off caliper then the new caliper ....then the brake pedal did the pedal several times then the wood stick off that brake pedal ..

so that caliper did not do the brake pedal down then you was the caliper new and then the brake fluid is air brake fluid and the master cylinder air !

the repaired changed ABS/calipers / and the brake lines brake pedal is down the floor ...

 

... the repaired changed ABS/calipers / and the brake lines brake pedal is down the floor ...

I get it, it's frustrating. But the simple reality is that hydraulics ALWAYS work unless something is faulty, so the trick is to find out what's wrong. Start with the basics: Do you have a fluid bleeder kit? Connect it to the FURTHEST (typically passenger side rear) caliper and SLOWLY suck out fluid and hopefully a little air. Next drivers side rear. Next passenger side front, then drivers side front. The nice things about the kit, they're cheap AND they suck (brake fluid that is). I always use the kit with the brake pedal UP, that way everything is open to the reservoir and there's no chance of sucking more air past the seals. Sorry you're having trouble, I'd be glad to help you if you were closer. I did my 08 Silverado last year and yes, they can be a bit annoying.

 

I was having so much trouble, I finally bought one of those compressor driven vacuum pumps. It turned out to be more than I needed. I did need to put some grease around each bleed screw while it was loose because I was sucking air past the threads so it was hard to tell when I was sucking air out of the brake line or sucking air past the threads. You could also go with "I've sucked enough brake fluid out by now the air has to be out". Which reminds me to say - make sure you keep checking the brake fluid reservoir and refilling it. And whatever you do, don't be like me and try to have someone pump the brakes while you bleed unless you put the reservoir cover in place first, and then you have to remove it to check it all the time. That's why vacuuming is easier as has been stated. I did it 3 times before I was satisfied...Glad you got yours straighten out too, I'm just kinda leaving this here in case someone else comes along looking.

 

the GM after the ABS vehicles take fuse off and flush it off brake fluid ...
the the brakes very good of the flushing of the brakes .. then the ABS fuse on ...

 

Had the same problem with my '88 K1500 after replacing a brake line. Pedal didn't go to floor but wouldn't firm up, couldn't bleed brakes. My buddy's dad said try tapping on the side of the master cylinder. He was a mechanic for many years, and he was right. Brakes bled easily after that, no further issues.

 

did the rear drums of the shoes did the pistons .leaking it ....
did the trailer brake shoes pistons leaking it 4 years ago ...