Help with brake line flare nuts

[JHZR2]

I have a thread on repair of my 2008 MB ML320, but this is more general, so I’m making my own thread.

Here is a failed bubble thread line and nut:

Note the flatness of the bottom of the flare, and the squarish shoulders of the nut.

Now, compare to two nuts I’ve received that are supposedly for bubble flares:

Note how they have a tapered inner diameter?

The right one is OE, the far left is AGS and explicitly says bubble on the box. The middle is SURR, and is supposed to be for bubble.

I don’t think I’m crazy either. It seems that the photos at Advance verify this:

Look at the squarish inside. Is it generally acceptable to use a fitting that has that taper inside? The rest looks the same…

I thought that the Asian M10x1.0 inverted flare type nuts had threads to the very end??

How frustrating. Any insight would be great.

 

[Trav]

Those are for old SAE bubble flares, yours has DIN bubble which needs a lead in on the nut. Go to NAPA or AA and see if they have the correct ones, if that fails call fed hill.

 

[JHZR2]

Those are for old SAE bubble flares, yours has DIN bubble which needs a lead in on the nut. Go to NAPA or AA and see if they have the correct ones, if that fails call fed hill.

View attachment 279772

Just got back from AA again. Nope, they’re all like that too. SURR and AGS branded. Including on all the finished bubble flare lines. They all have the lead in on the nut. Just that slight taper in the ID.

Must be a “good enough for parts consolidation” scenario, for which I’m not a fan. All photos show the squared ID, all the parts at multiple stores show the taper.

Stupid NAPA closes early, but they’re open tomorrow AM, so knocking on wood. Otherwise another week.

 

[JHZR2]

 

[JHZR2]

Those are for old SAE bubble flares, yours has DIN bubble which needs a lead in on the nut. Go to NAPA or AA and see if they have the correct ones, if that fails call fed hill.

View attachment 279772

I just ordered line and fittings from fedhill.

If the fittings from them have a taper I’m going to go insane.

Also just realized that the tooling to do a bubble flare (which apparently is the same as the first step in ann sae inverted flare) isn’t the same as to do a DIN bubble. FWIW…

Maybe again, the taper on these metric nuts is sufficient. I don’t care to find out.

 

[eljefino]

What's wrong with your old nut? Wire brush it and see what you get.

 

[Trav]

I just ordered line and fittings from fedhill.

If the fittings from them have a taper I’m going to go insane.

Also just realized that the tooling to do a bubble flare (which apparently is the same as the first step in ann sae inverted flare) isn’t the same as to do a DIN bubble. FWIW…

Maybe again, the taper on these metric nuts is sufficient. I don’t care to find out.

I would call fedhill first thing monday and tell him what you have and send a pic over if he needs it.

 

[JHZR2]

What's wrong with your old nut? Wire brush it and see what you get.

It was corroded to the line. It was mildly rounded at the corners.

And I need two more for a union. I can get the MB unions cheap and easy, not the fittings…

 

[D60]

Does not help with the line but for the nuts, how critical is OAL? Can you just face it until the c-sink is eliminated?

 

[JHZR2]

Does not help with the line but for the nuts, how critical is OAL? Can you just face it until the c-sink is eliminated?

Huh? Not sure I get the question. Length doesn’t seem to be an issue. They all seem to be the same length.

The issue is if the taper on the ID of the male fitting makes a difference with a DIN flat bottom bubble flare.

 

[eljefino]

Does not help with the line but for the nuts, how critical is OAL? Can you just face it until the c-sink is eliminated?

The female threads it goes into do eventually stop, so that length is important. Otherwise I say find a sanding wheel and make up a jig.

 

[eljefino]

It was corroded to the line. It was mildly rounded at the corners.

And I need two more for a union. I can get the MB unions cheap and easy, not the fittings…

What do you mean you need two more for a union? Unite any way you want-- hint, double SAE flare, the industry standard.

Yeah the corners are rounded, but you got it out, it'll go back in. Run a drill bit through the middle to clean out any rust.

 

[D60]

The female threads it goes into do eventually stop, so that length is important. Otherwise I say find a sanding wheel and make up a jig.

But you'd see the threads below the hex vanish, no? At which point it would be a clue you've ran outta thread??

I think you want it square, I wouldn't sand it personally-- even w a jig. I'd use the big metal thing with a headstock, chuck, carriage and tool post

 

[eljefino]

But you'd see the threads below the hex vanish, no? At which point it would be a clue you've ran outta thread??

I think you want it square, I wouldn't sand it personally-- even w a jig. I'd use the big metal thing with a headstock, chuck, carriage and tool post

Yeah a Bridgeport would work well and completely be the BITOG answer.

 

[burbguy82]

which die do you have?

 

[JHZR2]

What do you mean you need two more for a union? Unite any way you want-- hint, double SAE flare, the industry standard.

Yeah the corners are rounded, but you got it out, it'll go back in. Run a drill bit through the middle to clean out any rust.

The FSM has the instruction that one union is allowable with DIN flare. MB sells the unions. The nuts are a bit tougher to find.

I need to cut the original line at a good spot, Flare that make end with a nut, then fabricate a new line, flare both ends, connect one to the union, the other to the brake hose.

Thus I need two more in addition to the one at the brake soft hose.

But you'd see the threads below the hex vanish, no? At which point it would be a clue you've ran outta thread??

I think you want it square, I wouldn't sand it personally-- even w a jig. I'd use the big metal thing with a headstock, chuck, carriage and tool post

Im still not grasping the question about threads. With a flare and the nut, there’s enough threads still exposed. All nuts I’ve gotten thus far are the same length. Not interested in sanding or milling them…

which die do you have?

I have a tool that does a din bubble flare, which is the issue. The DIN flare has a fully flat bottom, and the nuts available everywhere have a taper in the ID. Maybe they’re more universal? Maybe they’re good enough? I just don’t know or understand. OE has a square ID on the nut so that’s what Iwant…

 

[JHZR2]

I would call fedhill first thing monday and tell him what you have and send a pic over if he needs it.

So, apparently every single auto parts store, and the major manufacturers who sell these parts, are putting the population at risk.

Per FedHill:

So it looks like DIN requires a squared ID, while parts stores selling “Euro” fittings for bubble flares are wrong.

Perhaps in the big scheme of things it doesn’t matter, but for a safety critical system like brakes it’s not a good spot to find out.

 

[burbguy82]

The FSM has the instruction that one union is allowable with DIN flare. MB sells the unions. The nuts are a bit tougher to find.

I need to cut the original line at a good spot, Flare that make end with a nut, then fabricate a new line, flare both ends, connect one to the union, the other to the brake hose.

Thus I need two more in addition to the one at the brake soft hose.



Im still not grasping the question about threads. With a flare and the nut, there’s enough threads still exposed. All nuts I’ve gotten thus far are the same length. Not interested in sanding or milling them…


I have a tool that does a din bubble flare, which is the issue. The DIN flare has a fully flat bottom, and the nuts available everywhere have a taper in the ID. Maybe they’re more universal? Maybe they’re good enough? I just don’t know or understand. OE has a square ID on the nut so that’s what Iwant…

There is a difference bewtween what you want and what is there. The mating surface of the flare should be the same. The square fitting and the square tool should work.

I thinbk this issue could be fixed if you got the correct tool.

Sorry if I am misunderstanding

 

[Trav]

So, apparently every single auto parts store, and the major manufacturers who sell these parts, are putting the population at risk.

Per FedHill:

View attachment 280102

So it looks like DIN requires a squared ID, while parts stores selling “Euro” fittings for bubble flares are wrong.

View attachment 280103

Perhaps in the big scheme of things it doesn’t matter, but for a safety critical system like brakes it’s not a good spot to find out.

So Fedhill got you all sorted out with the right parts? These parts store should not be selling SAE flare hardware for DIN/ISO. Throw a Girling in there and go to one just for fun.

 

[JHZR2]

There is a difference bewtween what you want and what is there. The mating surface of the flare should be the same. The square fitting and the square tool should work.

I thinbk this issue could be fixed if you got the correct tool.

Sorry if I am misunderstanding

There’s a damaged part - an OE DIN bubble flare, and an OE line nut. The line nut has squared shoulders of the inner diameter where the flat bottom of the DIN Bubble would sit.

Every single part from manufacturers has that taper in the inner diameter. They all claim to fit my vehicle, all claim to be for European vehicles, etc.

Either the significantly reduced contact area on the flat backside of the bubble flare is irrelevant, or every single part sold anywhere that I’ve looked is wrong.

So Fedhill got you all sorted out with the right parts? These parts store should not be selling SAE flare hardware for DIN/ISO. Throw a Girling in there and go to one just for fun.

Well they verified that the bubble flare nuts have the squared inner diameter shoulder. So I fuel I’ll get the right thing…