Stripped brake line fitting edges

[faof2]

91 Volvo 240 non-ABS brakes auto trans 112,000 miles.

BACKGROUND - I replaced one of the two front left brake hoses because it was bulging a bit at the bottom (wheel side). The fitting attached to the steel line at this end was tight. I persisted using the proper flare nut tool (11mm I believe) for automotive line fittings and it finally broke loose. The other end (toward the master cylinder) was not so stubborn, but it took some effort to break it loose. After replacing one of the two hoses, I decided to replace the other one because it too had a slight bulge at the bottom. The fitting at the top end of the hose broke loose fairly easily. Then I went for fitting at the lower end of the second hose again using the flare nut tool .It would not budge and as I put more pressure on it, the wrench just rounded off the fitting. So as not to be without brakes, I stopped at that point, applied Liquid Wrench, gravity bled the three nipples on the caliper, and put the wheel back on, meanwhile wondering how I was going to change out that brake hose. I thought I might purchase the steel line that goes from the end of the hose into the caliper and with that in hand make another attempt to remove the fitting from the hose using a pair of Vice Grips .I’ve heard too many stories of vice grips ruining such a fitting. I figure if all fails, I can cut the steel line and replace it with the new one. But I would rather not assume that will all go smoothly. (What if the other end of the steel line is just as stubborn?)
QUESTIONS:
1. How could I have prevented this problem? (I will be doing the other side some day, and I do not want to have a repeat.)
2. What would you do at this point?
3. If I use vice grips, what suggestions might you all have to not destroy the fitting?
4. Is there a tool that would be superior to a vice grip for this application?
5. Will penetrating oil actually help in this situation? I’ve not found it particularly useful myself in other situations, though I am aware that others swear by it.
6. Would it be realistic to think that I could file down the fitting on all six sides so that the next smaller size wrench (10 mm) would fit?
7. What size SAE wrench would be tighter (smaller) than 11 mm?
I look forward to your suggestions.
Jerry

[difflock54]

I had this problem with my previous vehicle. (a 96 Toyota Rav4.)
The top end hose connection to the brake line stripped the corners off the nut allowing the open end flared spanner to slip.
I used a very small vice grip and aligned the jaws carefully on the flats.
I then gave a gentle single sharp tap with a rubber hammer and was able to free the nut okay.
I must confess to replacing it after renewing the rubber hose, rather than replacing the damaged flared nut as I had to get the vehicle back on the road promptly.
The nut was lightly re-threaded on okay with the correct open end spanner but i then 'torqued' it by fitting the vice grip and gave a single non aggressive hammer tap, just sufficient to give a tight fit required.
These brake line nuts seem to be fabricated from quite soft metals and are not robust. I think the open end spanners also can flex open as opposed to a full circumference ring spanner, thus slipping and stripping the flats off when too firmly forced.

[lummert]

Volvo OE brake line fittings appear to be brass.