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Freeing Frozen Brake Line Flare Nuts?

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New User

Nov 28, 2016, 1:52 PM

Post #1 of 7 (2307 views)
Freeing Frozen Brake Line Flare Nuts? Sign In

Hello all,

This is more of a general wrenching type question. I found a leaky, rusted out brake line at the left rear wheel of my 1990 Chevy C-1500 PU. I've assembled the replacement lines and hose and gotten the nut at the wheel cylinder loose, but can't get the nut at the other end of the line loose. I'm using a brake nut box wrench, but still managed to round the corners off it, then further mangled it using a vice grip. Likewise where the flex hose joins the line running forward to the master cylinder.
I expected to replace the flex hose and both lateral lines, but now am stuck until I can figure out how to back out these frozen nuts. I've tried penetrating oil and gentle hammer tapping, but nothing is freeing these 26 year old nuts.
Any of you mechanics have any suggestions? I really don't want to tow it to the nearest garage after all this work and expense.


kev2 profile image

Nov 28, 2016, 2:12 PM

Post #2 of 7 (2302 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

Heat - torch.
My choice is PB blaster penetrating. But its already rounded -
You are at differential ? maybe try removing flex hose then can hold nuts and spin 3way fitting... But often replacement of lines necessary

New User

Nov 28, 2016, 2:17 PM

Post #3 of 7 (2299 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

Yeah, I've already worked a bit on removing the flex hose but stopped before messing it up too. Yes, I'm at the differential. I guess a torch would be safe enough. The tank is a few feet forward of this.

Thanks for the reply!

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 28, 2016, 2:35 PM

Post #4 of 7 (2287 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

Torch - Oxy/acet with fine point tip but many toss all the lines anyway.

Trick 4 U. When stuck it's the line inside the flare not the threads. Just take good snips, wire cutters or what works and snip line right off then you can treat the flare like a bolt, even rounded you should be able to get it out.

Side note or caution is bend new lines so they are exactly where old ones were no wobbling around. Practice with the flaring tool on a pre made longest line you can find and use unions not compression fittings.

Trucks this is routine and many cars as well 20 years newer than this,


New User

Nov 28, 2016, 4:05 PM

Post #5 of 7 (2266 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

Just hosed all the nuts down with PB Blaster and will let them soak overnight. If that doesn't do the trick I'll move on to the more extreme measures.

Many thanks for the great input, guys!

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Nov 28, 2016, 4:12 PM

Post #6 of 7 (2264 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

When you do get them free, they will not come loose all at once. You have to just keep working them back and forth and it will keep getting looser and looser.
Make sure it is not frozen to the line as you will twist it right off.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 28, 2016, 11:43 PM

Post #7 of 7 (2252 views)
Re: Freeing Frozen Brake Line Flare Nuts? Sign In

You said up earlier that a line let go and the flare nuts are where you get stuck. Just do the entire line IMO and not try to save it at all. This is way too common and if you don't watch them all - fuel lines, evap lines, some transmission cooler lines they'll all start going.
PB all of them now then use spray grease on the flares or they'll all give you fits. Fuel filter too not a maybe , will give you fits so lube it now and plan on a fight.

Strong suggestion when these are stuck in a hose, another line, caliper or wheel cylinder toss those too - dirt cheap as things go. Making up lines, cutting to length and flaring ends the tools are cheap as well just takes time to get just right and more important that the holding hardware be fixed or use something so they don't whip around or rub anything or fail quickly.

Just fussy to do not costly for tools or the lines. Brass unions or adaptors as needed can add up more than line will. I choose to buy the longest pre made line and cut to size, others buy this buy the roll to do all lines. Problem is the rolled line IMO again is cheap and rusts faster than the pre-made line and pre-made ones you get two flare nuts to use you don't need to buy new which can cost as much as the line each!
Practice with new clean stuff bending it with tools, hands, wood like hammer handles held in a vise or whatever. This is too important to not get right and cheap enough as said. If one went you be doing others so keep the tools!


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