rounded nut on brake line.

I'm attemting to disassemble my brake lines to sub in a braided set, and one ******* fitting is resisting. The bike is a naked with ABS, and the first line from the m/cyl attaches to a metal tube which leads back to the ABS 'machinery' under the seat. The junction consists of a metal cube about 20mm per side, bolted to the frame, threaded female, with a 10mm nut on the end of the tube, threaded male to join into the block. There is very little clearance to work with to get at the nut, and it rounded off when I attempted to back it out. You can see the nut and the block in the detail shot of the right front of the frame , below.







The nut needs to remain functional, cuz it'll be needed to reattach to the new brakelines, so it's not just a matter of cutting it off with a Dremel or chizelling an edge and 'driving' it free. I can't try to break it free with heat from a torch cuz of all the wiring etc nearby. I can back out the 8mm bolt that holds the block to the frame and get a little bit of room to work with, but I'm not sure there's enough room to get a set of "Nutbuster" pliers onto it. The 10mm wrench from the Suzuki toolkit that I used was not a very tight fit to the nut, and I think that was big part of causing the rounding. Perhaps if I got a closer tolerance 10mm wrench? Or maybe teamed two wrenches, or got one with a broader working face? (The Suzuki wrench is only about 4mm broad, and the faces on the nut are more like 7mm...). Maybe a 12/32" wrench (= 0.375 inch) or 25/64" (if such a thing exists = 0.3906") could be forced onto the 10mm fitting ( = 0.3937"). Or maybe I could buy a good quality closed end 10mm wrench and cut a slot in the back end so that it would fit over the 4mm line leading out of the nut, then work it onto the nut? (I presume it would take a grinding wheel to cut wrench quality chrome vanadium steel?)

I'm not sure what other options I have... Penetrating oil, of course... A shock-hit with a hammer...

Any other suggestions? Any one have any experience with a similar situation?

If I was you I would use a bolt extractor kit like the once below, then go to your local fastener shop and show them the bolt and they will replace it with a stainless steel one or what ever they have closest to yours. Also spray a bit of lub in there like GT85.

thanks endo, but (a) the nut is not accessible from end-on, and (b) it needs to survive the loosening. I edited the original photo to circle the nut in question, as you must be misunderstanding which nut I'm having trouble with.
cheers,

Could you undo a different fitting like the other end of the black hose on the right, undo the bolt to release the block and then feed the whole unit out into the open maybe under the tank and get a spanner on the block and some mole grips on the rounded end? I don't have this model but access to the rounded part seems to be the problem.

[Nobbylad]

If you unbolt the block from the frame, can it be moved further towards the front or rear of the bike for you to work on? Presumably if you remove the lever and m/c you can move them closer to the frame and pull the block through to a more workable space?

[rictus01]

your first mistake was as you've said, using the bike toolkit should be a last resort not a first one, if you've badly rounded the nut off then even a decent normal spanner isn't going to help much, however you can get spanners that grip on the flats not using the corners, one of those may do, short of that needle nose molegrips would be another option.

Cheers Mark.

[keith_d]

Can you undo the other end of the brake line and the bolt holding the block to the frame. Then slide the whole assembly out to get a bit more working space and try another set of flats.

I've had a similar problem with a rounded nut on a car brake assembly and ended up using a tool which cams onto the nut, so the harder you push the more it bites onto the nut. Something like a cross between a stud extractor and an adjustable spanner. Effective but I had to replace the brake line afterwards.

IF the nut isn't re-usable you might be able to get a made to measure brake line in your local car shop.

Looking at your photograph I would suggest that you firstly remove the bolt that attaches the "block" to the frame, this should then give you more room to ATTACK the rounded off hose/union that appears to enter the block. Firstly try with a correctly/tight fitting open ended spanner if that still wont work use a pair of well adjusted "Mole type" grips. IT IS ALWAYS WORTH VERY CAREFULLY TIGHTENING by a small amount before undoing.
If you support the "block" with a suitably sized open-ended spanner this will support whilst attempting to undo. Thats of course IF my comments make any sense.

Best of luck JOHN

[Sid Squid]

Presumably the spanner you used was open ended, as such it only drives two of the six flats of the nut, if so the rest of the nut sould be OK
It would be best to remove the whole assembly, (this may sound a faff - but it's better than damaging something else as well), and also go get a tool called a flare nut spanner, which looks like this:

thank you all for your contributions - much appreciated. i CAN remove the bolt holding the block to the frame and get SOME more room to work, but it's quite limited, maybe no more than 15mm-20mm. the tube (brake line) runs from the fitting back to the ABS unit under the seat, and it's long, convoluted, and reasonably rigid. for edification, here's the schematic:




the part in question is the nut that secures the brakeline into the block at the end of hose #1. the brake line back to the ABS unit is like most brake lines, not flexible...


particular thanks to sid squid - I think a nice tight fitting 'flare nut spanner', with the block loosened up for extra working room, might do the trick. I had no idea such a tool existed, which is why I was thinking about buying a closed-end wrench and grinding a slot in the back end. brilliant. i'll report up once I have a go ( it'll be a few days till i can get to it...)