Brake pedal goes to floor

[Oakley Vest]

So I just installed a Rough country 6 inch lift on my 03 Silverado 1500. I unhooked all the break lines at the calipers to do the lift. When I got everything put back together it was time to bleed the breaks. When I tried they pumped up like normal but after starting up the truck the pedal then sank to the floor. I’ve done this a good 10 times to no avail. My abs lights are on in the cab as well as service break system, but all these lights where still on before I lifted my truck. I even changed out the master cylinder an tried to run the codes on my scanner. But it said that I had to clear trouble codes before I could do the automated bleed. But It won’t let me clear the codes anyway. I do have breaks but there almost absolute. Is there a way to bypass abs so I can have breaks again? I’m lost! 

[davester]

It's not the abs system that's causing the problem.  The abs bleed procedure only gets rid of any air in the abs controller itself, which is a pretty small amount.  If the pedal is going to the floor, the problem is elsewhere.

 

Did you go through the whole bleeding process, from bench-bleeding the master cylinder, to bleeding the wheels furthest from the MC to the closest?

[Oakley Vest]

16 minutes ago, davester said:

It's not the abs system that's causing the problem.  The abs bleed procedure only gets rid of any air in the abs controller itself, which is a pretty small amount.  If the pedal is going to the floor, the problem is elsewhere.

 

Did you go through the whole bleeding process, from bench-bleeding the master cylinder, to bleeding the wheels furthest from the MC to the closest?

Yes already did that. Bleeding while truck isn’t running restores the breaks. But when so start it up all the pressure goes away. 

[Doug_Scott]

Starting the truck enables the power brake booster.  Does your truck have traditional vacuum brake assist or is it hydraboost?  

Have you tried bleeding with the engine running?

When you disconnected the brake lines, did it empty the master cylinder? 

You say the warning lights were on prior to you disconnecting the lines, is that what you intended to mean? 

You are going to need to start by bleeding the master cylinder correctly.  Take it off and bench bleed it until there are no bubbles from the two lines.  Put the master back on and bleed the connection where the two steel lines attach, but, do not pump the brake pedal when bleeding these two lines, just have the person push the pedal down slowly while you crack one line open. Start with the rear line on the master. Close the line before the person releases the pedal. Repeat on the front line.  It's important to not pump the pedal when doing the one part of the bleeding. 

Bleed the rest of the system starting at the right rear, and move to the left rear, then right front, and finally left front.  Do not let the reservoir go empty.  If you still have a low pedal, clamp off the 3 flex lines and see if the pedal gets better.  The hose that makes the largest difference to the pedal is where the air is.  Keep in mind that the trapped air is after the flex hose if clamping off makes a difference. 

[diyer2]

Buy a brake bleeder.

 

[Oakley Vest]

3 hours ago, Doug_Scott said:

Starting the truck enables the power brake booster.  Does your truck have traditional vacuum brake assist or is it hydraboost?  

Have you tried bleeding with the engine running?

When you disconnected the brake lines, did it empty the master cylinder? 

You say the warning lights were on prior to you disconnecting the lines, is that what you intended to mean? 

You are going to need to start by bleeding the master cylinder correctly.  Take it off and bench bleed it until there are no bubbles from the two lines.  Put the master back on and bleed the connection where the two steel lines attach, but, do not pump the brake pedal when bleeding these two lines, just have the person push the pedal down slowly while you crack one line open. Start with the rear line on the master. Close the line before the person releases the pedal. Repeat on the front line.  It's important to not pump the pedal when doing the one part of the bleeding. 

Bleed the rest of the system starting at the right rear, and move to the left rear, then right front, and finally left front.  Do not let the reservoir go empty.  If you still have a low pedal, clamp off the 3 flex lines and see if the pedal gets better.  The hose that makes the largest difference to the pedal is where the air is.  Keep in mind that the trapped air is after the flex hose if clamping off makes a difference. 

I believe it has traditional vacuum break assist. Yes, I have tried bleeding while truck was running, and doing that didn’t build up any pressure at all. Yes it did empty the master cylinder. And yes warning lights have always been on since I bought the truck but they never caused any problems before this. Thank you I will try that.