Rear brake drag/caliper failure/hose

[oblivionnewtonjohn]

2003 KJ Sport:

On my commute home, I noticed smoke and then smelled the fluid. I get home to see the rear drivers side Jeep center cap has melted off it's mounts, lugs are super hot, rotor looks gnarly. Oddly, I notice fluid in both rear fender wells.

From my brief inspection, the hoses and lines look to be intact. I won't know until tomorrow morning as I am on the clock at the moment.

I will put on jack stands, see how rear wheels turn. I assume new caliper, rotor, pads, bleed the system as I am sure the fluid got boiled?

What are some diagnostic test to check the hoses?


After I replaced suspension this past summer, I had the brakes bled, tech mentioned a bad bleeder valve, may call to see if their paperwork notes which caliper.

 

[RenKJ]

if I were you I would put an order in for a new caliper straight away, the piston will not have survived overheating that bad and piston seizing is probably what caused it in the first place.

 

[oblivionnewtonjohn]

if I were you I would put an order in for a new caliper straight away, the piston will not have survived overheating that bad and piston seizing is probably what caused it in the first place.

Oh that's a given, I am mainly concerned whether the hoses need to be replaced. I'll know more tomorrow when I inspect further.

As I said, I had the system flushed this past summer. Maybe it was simply a caliper piston failure and not trash in the line.

 

[duderz7]

If you're already replacing the caliper and concerned about the hose I'd go ahead and replace it. Soft hoses do go bad. It would be better than doing the job twice.

 

[JasonJ]

Oh that's a given, I am mainly concerned whether the hoses need to be replaced. I'll know more tomorrow when I inspect further.

As I said, I had the system flushed this past summer. Maybe it was simply a caliper piston failure and not trash in the line.

If you're already replacing the caliper and concerned about the hose I'd go ahead and replace it. Soft hoses do go bad. It would be better than doing the job twice.

Agreed.. they're really just layered rubber and thread reinforced... they will and can melt, the inner layers can collapse and cause a one-way valve scenario that causes a caliper to lock up and fail to release.

Given what you are describing, just change them... relative to the cost of what's needed already, it's small and a proper way to make sure the same issue doesn't reoccur.

Don't cut corners or shortcuts with brakes.. that's for sure. If it's questionable, don't question it... replace it.

 

[oblivionnewtonjohn]

After reviewing further, it's definitely drivers rear caliper. The rotor on that side I replaced this past summer as a set is discolored, appears to have heated up quite a bit. Smelled heavily of brake fluid though I saw no leaks. I assume piston failed and squirted out, burning up from the heat? Still odd I had fluid in both rear wells, but see no signs of it on the axel. No sign or smell on the passenger brake assembly.

The rear passenger is fine though I noticed a tad bit of drag in one spot when rotating with the drivers side completely disassembled.

Should I bite the bullet and replace passenger rear caliper as well just to deal with it all at once?

You make a good point about the hoses and I will replace for good measure.

 

[tommudd]

After reviewing further, it's definitely drivers rear caliper. The rotor on that side I replaced this past summer as a set is discolored, appears to have heated up quite a bit. Smelled heavily of brake fluid though I saw no leaks. I assume piston failed and squirted out, burning up from the heat? Still odd I had fluid in both rear wells, but see no signs of it on the axel. No sign or smell on the passenger brake assembly.

The rear passenger is fine though I noticed a tad bit of drag in one spot when rotating with the drivers side completely disassembled.

Should I bite the bullet and replace passenger rear caliper as well just to deal with it all at once?

You make a good point about the hoses and I will replace for good measure.

Always replace in pairs , one will be new and working easier then the other if not , also be a good time to replace the flexible hoses back there to be sure. Cost a bit more but will save headaches later

 

[dillon]

Agreed.. they're really just layered rubber and thread reinforced... they will and can melt, the inner layers can collapse and cause a one-way valve scenario that causes a caliper to lock up and fail to release.

I have had that exact thing happen before, took a bit to realize what was happening.

 

[LibertyTC]

Agree with Tom.
Brakes are not something you want to cheap out on. Calipers, lines, rotors, pads etc.
My rear brakes were completely re-done, and years later, still in good reliable shape.
If the e-brake is a rotor/in hat design, new spring kit & pads there too.

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I like to inspect all brakes once a year.

 

[oblivionnewtonjohn]

I got rear brake hoses, gees they are hard to separate even after soaking in Kroil. I tried a flare wrench, line wanted to twist on me so I stopped, not enough room at the bottom to hold with vise grip and wrench up top.

Hard lines are NLA so I am worried, how do I separate the flare nuts?

 

[ltd02]

I got rear brake hoses, gees they are hard to separate even after soaking in Kroil. I tried a flare wrench, line wanted to twist on me so I stopped, not enough room at the bottom to hold with vise grip and wrench up top.

Hard lines are NLA so I am worried, how do I separate the flare nuts?

When I did my 02 rear wheel cylinders years ago (Drums on the 02), I think the vinyl coating on the hardlines had fused the nut going to the wheel cylinder. i wound up replacing the hardline back to the junction block on the diff. I took the old one and measured it's length and took the end fittings to NAPA and matched the length and ends with some straight preflared ones. These new style brake lines are super easy to bend without kinking if you take your time. Use an old coffee can or something for the bends. This was not really a bad thing in my case since the hardines were getting sketchy. If you need to do this too then just cut the hardline at the nut and put a 6 point socket on them to get it off the caliper. Don't horse it off, just steady pressure to break them free.

 

[oblivionnewtonjohn]

When I did my 02 rear wheel cylinders years ago (Drums on the 02), I think the vinyl coating on the hardlines had fused the nut going to the wheel cylinder. i wound up replacing the hardline back to the junction block on the diff. I took the old one and measured it's length and took the end fittings to NAPA and matched the length and ends with some straight preflared ones. These new style brake lines are super easy to bend without kinking if you take your time. Use an old coffee can or something for the bends. This was not really a bad thing in my case since the hardines were getting sketchy. If you need to do this too then just cut the hardline at the nut and put a 6 point socket on them to get it off the caliper. Don't horse it off, just steady pressure to break them free.

I have the brake assembly broken all the way down/separated. I cannot get the flare nut (top) on the soft hose to turn without the hard line/flare body (bottom) wanting to twist. I have tried a vise grip on the bottom flare body, not enough room for a regular box end 16mm wrench up top to get a sure grip on the nut.

You may be right, I may have to make new hard lines. Looking at the FSM it does not detail the process, I assume they consider it straight forward barring fusing/rust etc.

 

[ltd02]

I see what you mean. I'm still living in a drum brake world. I'd probably just give it a good turn and if the hardlines twist then just replace the hardlines too. I'm sure there is some way to get up in there to brace the hardline while turning but these things are made to go together. Coming apart is less important to the original assembly. I have a project vehicle with drums all around and I managed break the rusty 51 year old front soft lines free with channel lock pliers and a flare wrench. I had the room to do this though...

 

[oblivionnewtonjohn]

I have the hard lines off, rear drivers is 16" and rear pass is 42". I checked O'Reillys in which the closest they offer is 20" and 40" so too long and too short even if I get creative with the bends.

Unless I make up customer length lines.....no good deed goes unpunished.
I have them soaking in Kroil in hopes I can break loose and reuse them.

 

[ltd02]

The 20" would be okay. You can just bend them a bit where they are straight to make up that difference. I had a very long one and put a coil bend in it to take up the difference. If there is a place in the 42" where they have an excess bend that you could skip the 40" might work. Had that happen when I did my 98 Ranger rear hardlines. I've started buying a 25' section with fittings and bending and flaring my own these days.

 

[oblivionnewtonjohn]

I got 3/16 lines per NAPA database, 8"x2, 30" and 12" with union couplings. So, what size is the end that threads to the distribution block on the axle? Because 3/16 seems a hair small, wiggles. Different thread pitch on that end?

 

[ltd02]

I got 3/16 lines per NAPA database, 8"x2, 30" and 12" with union couplings. So, what size is the end that threads to the distribution block on the axle? Because 3/16 seems a hair small, wiggles. Is it 1/4 on that end?

The 3/16 is the line size but the end nuts can vary. Most common for SAE is a 3/8-24. I'm thinking my 02 took a metric M10 at the block. That was 7-8 years ago so not positive.

I've been using the following kit on my non-KJ project and you can see there are different size fittings for the same tubing. https://smile.amazon.com/gp/product/B07C8KHL59/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Probably something like this: https://smile.amazon.com/Steel-Tube...&sprefix=metric+brake+,automotive,153&sr=1-12

 

[oblivionnewtonjohn]

The 3/16 is the line size but the end nuts can vary. Most common for SAE is a 3/8-24. I'm thinking my 02 took a metric M10 at the block. That was 7-8 years ago so not positive.

I've been using the following kit on my non-KJ project and you can see there are different size fittings for the same tubing. https://smile.amazon.com/gp/product/B07C8KHL59/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Probably something like this: https://smile.amazon.com/Steel-Tube...&sprefix=metric+brake+,automotive,153&sr=1-12

Awesome, thanks. My stock hard and soft lines appear to be ok to me. I will reuse for now and invest in the two products you listed to redo my lines later. I don't have time to keep running to multiple stores trying to make up lines right now.

 

[oblivionnewtonjohn]

I decided to go with a new hard line setup, cheaper than sourcing parts, buying a decent flare tool, $35 shipped, will be here Friday:
https://www.ebay.com/itm/192476011155

I saw some OEM on the OEM Chrysler sites, rear passenger $46 IF it really is still in stock, BUT, drivers rear was $312!!

 

[oblivionnewtonjohn]

Lines appear to be of good quality, correct 3/8-M10 fittings, bends. Not bad for $35 shipped, made in Detroit.

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