2nd Gen Non-Engine/Transmission Brake trouble

[Sippy_The_Cup]

So I just finished changing ALL the brake lines on my truck to stainless steel and replaced the master cylinder and hydroboost. I bled the brakes using a motive power bleeder from genos garage. I bled till fresh fluid came out all four calipers. Started the truck, brake pedal goes to the floor and I have to pull it back up with some decent force. Turned truck off, pumped the brake, no pressure but the pedal would flick itself back up most of the way. Turned the truck on and pushed the pedal again. It went to the floor again but now is locked down and I can't move it back up at all. It feels like a mechanical hang up not like a vacuum lock or anything. I bled the power steering (turned wheel back and fourth till it stopped draining the reservoir) super stumped please help! Thanks!

 

[Hoefler]

Sounds like the hydra-boost is hanging up

 

[petersonj]

super stumped please help! Thanks!

For members to offer their best help, they need information about your truck - year model, 2wd or 4wd?, auto or manual, trans? miles on vehicle?, etc.

Also, were these repairs done all at once before testing operation after the repairs, or were they done independently? Why were so many repairs done (failed components?, mainentance?, problems?)?

- John

 

[Dan_69GTX]

For members to offer their best help, they need information about your truck - year model, 2wd or 4wd?, auto or manual, trans? miles on vehicle?, etc.

Also, were these repairs done all at once before testing operation after the repairs, or were they done independently? Why were so many repairs done (failed components?, mainentance?, problems?)?

- John

Ditto.

Hind sight - make one major change at a time. That way when something doesn't work - you know what it is.

Onto the repair....

Did you bench bleed the master cylinder? (It is recommended to do that - even if you are using a power bleeder.) How did it feel - Did the unit hang up at all or did the piston return as normal?

Does the pedal lock down when truck is running AND not running - or just...????

Did the pedal go down by itself or did you push it down?

Is the rod between the master cylinder and hydroboost adjustable? Did you adjust it to specs based upon your NEW parts (might need to be adjusted).

DID you put that rod back in?

Do you have any fluid come out of the bleeder when you press on the brake pedal?

Lots of more details are needed to know what you have or have not tried.

I've returned WAY too many parts in the past few years due to them being crap right out of the box.

 

[Sippy_The_Cup]

So to start it's an 01 2500 4wd nv5600 4 wheel abs and no load sensor. I blew a brake line and realized all the other lines were rusty as well so I figured I'd change them all and with 137k on it a new master cylinder (which was leaking where it mates to the booster) and new hydroboost wouldn't be a bad idea since it was all going to be apart anyway. I did not bench bleed the master cylinder which I realize now I should have done. I'm thinking the improperly bled master cylinder may be locking the hydroboost from being actuated? After bleeding the pedal would go to the floor with a really light touch but I'd have to pull pretty hard on the pedal to get it to come back up and reservoir fluid level never changed. Then the pedal locked down as I mentioned before. Thanks for the help and sorry for the initial vagueness

 

[Dan_69GTX]

You might need to remove the master cyl to verify it is fully bled. Should be simple to do, just not what you want to do.

Can you push to the floor WITHOUT the truck running? - If so, you still have air.

If it doesn't go to the floor can you get a hard pedal and get fluid out of a caliper bleeder WITHOUT the truck running?

Regarding the pedal movement. Are you SURE you put the hoses on correctly? If so, I'd question the new booster.

 

[B.G. Smith]

Could be the pedal rod length is incorrect (too long) and is activating the booster all the time. bg

 

[Bromiley99]

What order did you bleed your lines in? From what I understand you want to start furthest away an move towards the master. That would mean starting right rear, then left rear, front right, an finally front left.

 

[Dan_69GTX]

I believe the 2001 needs a scan tool to bleed the ABS unit. Did you do that?

If I remember, I'll see if I can verify that tonight.