'97 K1500 Suburban (JB6) Rear Brake Line Selection

So I lost rear brakes in my Suburban again yesterday... As the title states it's a '97 K1500 with the JB6 brake system

I was coming off of the interstate on my way home and noticed the pedal sinking lower than normal as I was slowing down on the exit ramp. I raised my foot and pumped the pedal once and it seemed to improve slightly. Came to a stop and made a right turn, then slowing down at the next stop light I heard a distinct "pop" sound and the pedal sank even farther than before. As soon as this happened the "BRAKE" warning light on the dash (same one to indicate that the parking brake is on) lit up and has stayed on constantly since. Pedal now goes almost all the way to the floor before it does anything, and there's not much there at all.

I managed to limp the truck home and get it parked on the street, but didn't get much of a chance to look at anything yesterday as it was pretty wet and nasty outside. I did pop the hood and observed that the brake fluid level in the master cylinder didn't appear abnormally low, which I thought was strange. Maybe the ABS module stops flow to a circuit if it detects a large pressure loss?

Today I went and looked underneath, and can tell pretty clearly that my passenger side rear hard line has sprung a leak near the spring perch. Same failure I had previously IIRC.

So I'm looking for opinions on replacement rear brake lines. I'd like to stick with stainless steel for durability. I see that Dorman has a complete hard line kit for my Suburban that claims to be "upgraded stainless," part number 919223. $135 on RockAuto.

Dorman 919223

I really don't think I need the complete kit, but that's a decent price for everything if I have other issues later. However I'm skeptical of Dorman part quality for all the usual reasons.

Inline Tube has just the rear lines that I need in stainless for $50, and I've heard good things about them.

Inline Tube SCTB95R5

They also have a complete stainless kit for $155 but again, I don't really need everything at the moment.

Inline Tube SNTB1015

If there are any other good options I'm missing please let me know.

I have a set of Russell braided soft lines for this truck and a leftover case of Wilwood 570 fluid, so I'm thinking it may not be a bad idea to throw those on and bleed the system while doing this as well. Any input/thoughts are appreciated.

I'd go ahead and replace all rear lines showing corrosion if I had the time (and money) to do so sonce you've already got to deal with bleeding the system.

No input on line type or brand here beside some kind of coated line.

I have personally had bad experiences with Dorman products. At my home and in shops I was in. I have had very good results with Inline Tube products and recommend their products when given the chance. I believe the "pop" noise was when the internal cups/seals in the master cylinder traveled farther than normal and now I personally would be worried about that master cylinder. It may work just fine but it would be a concern. IMO, I would at least do both sides at the rear.

movietvet said:

I believe the "pop" noise was when the internal cups/seals in the master cylinder traveled farther than normal and now I personally would be worried about that master cylinder. It may work just fine but it would be a concern.

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I did wonder about that...

RockAuto has a Raybestos master cylinder that fits my application (MC390259) for $38 and it's been confirmed that they're the current supplier for many GM brake parts. (The ACDelco equivalent is probably the same part, and is $83!) I might order one of those just in case.

Raybestos MC390259

df2x4 said:

I did wonder about that...

RockAuto has a Raybestos master cylinder that fits my application (MC390259) for $38 and it's been confirmed that they're the current supplier for many GM brake parts. (The ACDelco equivalent is probably the same part, and is $83!) I might order one of those just in case.

Raybestos MC390259

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For that price, I would just install it. Your choice of course. If you do, make sure you do a "bench bleed" before install.

I second the Inline Tube product. I replaced both of the hard lines on the rear axle of my GMC last year, no complaints and the price seems reasonable IMO.

Get some brake clean in the mean time and hose everything down.

The only piece of the Inline Tube full kit that I have on my truck is the rear axle portion. The rest got replaced with NiCopp. Some of the flares had burrs on them that would not seal regardless of how hard I tightened them.

Due to a crack in the line where it rubbed up against the axle, I R&Rd my rear brake lines on my Suburban (1999 K1500 5.7L, LT, JB6 Brakes) with SS Tubes TRA9521SS back in 2022-11.
They arrived well packaged and were a drop in replacement and had all the correct bends premade.

Only difficultly I had was on the brake cylinders, the threads were in terrible shape and I just could not get a good seal until I ran a tap (I believe 3/8-16 UNC, but don't hold me to it) in the cylinder's threads to clean them out.
Then the new lines threaded in smoothly, and sealed perfectly when tightened (5 side crowsfoot at 90° to the wrench, 13 [ft-lb] per the 1999 FSM, Pg. 5-140).

As an alternative to buying pre-made, consider buying cunifer pipe and a flaring tool. At 3/16'' this pipe is a common size and the same as the front lines. You have the option of new fittings or reusing the originals if in good enough condition. Admittedly I lean towards this on account of the sheer difficulty of getting long sections of pipe sent in the mail to the UK.

I recently had the rear line fail too and the same illuminated dash light. Didn't hear a 'pop' - not to say there wasn't one though. With pipe sorted, the dash light extinguished itself without any further efforts from me - but not immediately. No problem with master cylinder.

fancyTBI said:

The rest got replaced with NiCopp. Some of the flares had burrs on them that would not seal regardless of how hard I tightened them.

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A less than perfect flare in cunifer (NiCopp) will seal when tightened sufficiently. SS and steel are much less likely to oblige.

Pinger said:

A less than perfect flare in cunifer (NiCopp) will seal when tightened sufficiently. SS and steel are much less likely to oblige.

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Correct. And I was past the warranty window to get new ones. I also didn’t have a flare tool that would adequately flare SS.