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Brake Line replacement

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I have a 03' Yukon XL AWD w JL4, and like others my brake lines are toast.  My plan is to replace everything from the combination valve down.  To make things easier, I am looking at the NiCopp lines.  I like the EZ-Fit kit, which includes lines that are pre-cut (not shaped) and flared with fittings.  It's more expensive than bulk tubing, but it seems like it might significantly reduce the time and effort involved.  I do have a couple of questions for those of you who have already tackled this job:


Material:  Any thoughts on NiCopp vs steel? Since NiCopp is much softer, should I go easy when tightening the fittings?  I think the specs call for 18ft/lbs of torque.  Does anyone have any experience with the EZ-Fit kit?

Bleeding:  I usually vacuum bleed my brakes.  Do I need a pressure bleeder to do this right?  Are there any tricks to completely bleeding the ABS module, or do I need a scanner to do it properly?  Do I need to bleed the master cylinder, since I am starting below the combination valve?

Routing:  It seems like the difficult line is the one going from the ABS to the rear.  I saw some articles about taking off the left wheel skirt to get a good angle on feeding the rear line.  Do you have any other tips re the routing of the lines? I don't want to have to drop the fuel tank or raise the body.

Tools:  Other than the pressure bleeder, I guess I need a flare nut wrench (14mm?), is a flex wrench important?  It looks like the access areas and angles on some of the fittings are tough.  Am I missing anything?


Any other advice?  I have attached a photo of the existing lines.  I am assuming that I don't have much time.  Let me know what you think.  


Thanks for all of your help!!!



Edited by ebk
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Thanks for your help, Starman!!  I ordered the Inline set.  Great price for the set, btw.  Also, do I need to get a pressure bleeder and a flex flare nut wrench (is this 14mm) to do this right?  Thanks again!!!

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I recently replaced the same brakes lines. I did not need anything special like a pressure bleeder. The brake lines can be difficult to remove from the ABS pump. 

Flare nut wrenches will not be much help - they will flex and slip on the nut. You may want to have some vice grips handy though. Don't over tighten anything.


Once the system is flushed and bled, clean all the fittings and then stand on the brake for 30 seconds with the engine running. Then check for leaks. Repeat several times. 







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I just replaced mine this week on my 2005 GMC Sierra 1500 Crew! Front passenger side blew out leaving a concert and the rest looked like your pictures. 

I went with the Dorman SS pre-bent kit from amazon I'm pretty happy with it. 

Step 1 - Buy a bolt cutters

Step 2 - Cut everything out gives you more room to maneuver the pre-bent lines into position.

I was able to fish everything into place w/o removing the bed or inching up the cab. I had the truck on jack stands on all 4 corners, removed the wheel wheel lining on the front wheels and also removed the plastic air intake and lower skid plate to make things easier. After I cut everything out I replaced in this order:


1 - Single line to the rear axle, this was easier than I thought coming in from the back end. took ~ 30 minutes to get into place and a pretty straight shot. It snapped into the factory mounts nicely.

2 - Passenger Front, this took ~ 45 minutes as I had to change my approach multiple times. Eventually coming from under the front of the truck, keeping the portion going to the wheel bent until I got the end to the ABS controller in good position to be maneuverable. 

3 - MC lines, pretty straight forward ~ 20 min each.

4 - Front driver, the easiest one ~ 15 minutes. 


I got most of the lines into their factory plastic holding clips except behind the drivers side tire/fender. Just no way I could replicate the routing from the factory. They are solid in place regardless.

I didn't replace the rear axle lines as they are in good shape and I didn't want to destroy the nice plastic brackets holding them in place. I did replace the front flex hoses just to not deal with additional rust and breaking parts. 

Over the course of the repair, I ran into issues with my rear drum wheel cylinders. The bleeders snapped right off. Ended up replacing those, and while I could have stretched my rear drums and pads a little bit more I opted to replace those as well (165,000 miles). My front pads, rotors and calipers were replaced last year. 

I got everything bleed, but had issues with getting the ABS controller to bleed so I had issues with a soft pedal. Ended up taking it to a shop for a final bleed as I was done crawling under the truck and I needed it running by this Wednesday for a business trip. Did that today, the shop complimented me on how well things looked. 


- By cutting everything out, I was able to put a deep socket on the ABS connections to get those out. Much easier then using a wrench. I connected everything from the outside back in. An offset flair nut wrench made final tightening at the ABS module easier. 
- Watch some youtube videos, helped me understand the routing and the various approaches to putting the pre-bent kit in place. Saved me some time solving that puzzle.
- The pre-bent made it hard to mix up the connections at the ABS, but realize there is a pattern of how the pipe needs to be intertwined for the ports to line-up nicely. I had to move the lines over/under each other a few times under there to get them to fall into place. 
- Make sure you have a full box of nitrile gloves, you'll go through them like crazy!
- Take your time, knowing that it would be a bit frustrating to get the lines in place kept my expectations of how long the repair would take in check. Getting the lines in was only half the battle. 

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20 hours ago, Paullys50 said:

By cutting everything out, I was able to put a deep socket on the ABS connections to get those out.


    Nice tip. I will cut the lines and use a socket at the ABS pump next time. That would be easier than vice grips. I only have one question: 


    Why the hell didn't I think of that!




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  • 1 year later...

I know, stale topic but 1 more tip.


I got an Amazon coated/prebent pipe kit.  Cutting the lines off at the ABS module and deep using a socket is the way to go.  But getting the new  line flare nuts to align/thread into the ABS block was a pain, what with the stiff brake line and all.  Chasing the threads (would be better performed with a real tap) with one of the cut-off flare nuts several times really helped.  Press the old brake line nub in to center the flare nut exactly where it needs to be (think: clutch alignment tool).  I had to do this thread chasing several times before I could get the old nut to run in smoothly.  This helped with the confidence factor getting the new lines in (steel flare nut, $500 aluminum pump block).


Torquing the new nuts was touchy as well ($500 ABS pump if stripped).  And no freaking way to get torque wrench in there, anyway.


Anyhow, after the initial bleed, finally got a hard pedal - but with seepage from the ABS block.  One was on the bottom (M/C connection) but also of course, the hardest one of the 5 connections to get to (upper/center).  I got a set of metric crow's foot wrenches, and I'll be dammed - it was 9/16th flare nut that the new lines came with.  Back to the tool store.  Anyhow standard crows foot with a 3/8th extension/ratchet, was able to honk it down a bit more.  Still seeped under really high pedal effort.  Honked it down a bit more, waaay uncomfortable with the thought of stripping.  And success.


Not stale topic: is anyone (roving mechanic) in the Chicago/O'Hare  area have a Tech II (or equivalent to cycle/bleed the ABS module)?

Edited by dye
accidental first save, typos
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