04 sierra brake lines

[green55]

Hey y'all -- i feel stupid asking this question, but I've never done brake lines and don't want to mess it up.

I have a mix of flexible, braided lines and hard lines coming from the master cylinder to the proportioning valve and then from the proportioning valve back to the ABS module. The lines from master cylinder -> proportioning valve look great.

The lines from proportioning valve -> ABS module don't look so great where they run along the frame. Should I replace these with entirely hard lines? I don't see anywhere that has an option with braided + hard line combo. I checked rockauto, etc

Attached pictures in case I'm not explaining well. Truck is a 2004 GMC Sierra Denali w/Quadrasteer, but I'm pretty sure the Quadrasteer part only makes a difference on the brake lines at the rear axle

 

[Blue85]

When I did my '05 XL, I bought the whole vehicle stainless kit (Dorman, I think). I didn't swap the lines from the MC, as you're saying. I liked the factory ones more than the hard lines that came with the kit. I don't think the flex is really important over the distance from that block to the ABS module. I suspect it's more for ease of assembly in the factory. Speaking of which...pre-bent lines sound great on paper, but can only be installed as-is if you remove the body from the frame. Leaving it alone, you'll be bending and rebending the lines 10x to get them snaked through where they need to go.

Do you have a bi-directional scan tool? Bleeding the ABS is hard without one. I ended up pushing tons of fluid through until I could get some semblance of brakes. Then I'd skid the truck on gravel (i.e. my driveway, my road) a few times, bleed more and repeat. I think the key is to get ABS active at all 4 corners (or at least any you've let air into).

Unfortunately, when I did this, I only replaced the front lines and now it's blown a rear line, so I'll get to do all of this bleeding again.

 

[green55]

Yeah I've watched a bunch of youtube videos of people doing it and the general opinion is that it sucks to do with pre-bent lines and needs a lot of patience. But it does seem doable on the trucks with maybe just detaching the bed from the frame to snake the rear line. TBD when I get in there -- things are almost always harder than people make it seem on youtube.

I don't have a bi-directional scan tool. But maybe this will be an excuse to get one bc that plus lines will still be cheaper than what the shop would charge to do it all.

I may postpone this for a bit. I need to do it soon-ish but urgency dropped some. I was originally going to tackle now because I was replacing a bad torsion bar crossmember mount and couldn't lift the crossmember enough to get the old mount out. The torsion bar hit the ABS module before I got enough clearance. Options were to remove the torsion bar or the ABS module. I noticed that my brake lines looked pretty bad, so figured I'd do the lines, remove the ABS module, replace the torsion bar crossmember mount, put it all back together. Once I looked into doing the brake lines, seemed like it may extend the project more than I wanted so I went for the torsion bar and was shocked that it actually came out pretty easy and wasn't rusted in place.

So the truck is back on the road for now and need to find another good time to bring it down for a bit. I'd like to get all of the small things squared away soon on my 04 so I can start to tackle the rust on my 89 Jimmy. Looks like our squarebodies are pretty close to twins based on your profile pic.