Using heat on stuck brake line and gas line fittings, how much real fire risk?

Hi everyone,

So right now my car has been marooned in the garage on jackstands for over a year without much progress, because as you can expect for a 30 year old car I have a bunch of seized brake line and gas line fittings preventing me from finishing my brake and suspension work and gas tank replacement.

Basically all 4 of my brake line fittings for the hard line to flexible brake lines are seized up, and an even bigger slap in the face is the fitting for the fuel accumulator (braided stainless line to the main fuel hard line). I have tried proper brake line flare wrenches, PB Blaster, Kroil, etc. and CRC Freeze Off to no avail to get these loose. I'm pretty much at the point where I probably need heat or to cut things out and replace them. All easier said then done when you the car is on jackstands in a one stall garage instead of on a lift or with the motor pulled and the body on a rotiserre.

By this point the car has been sitting this way for over a year (without a fuel tank on it) and the rear flex lines were cut so it's pretty safe to say that almost all if not all of the brake fluid and the gas has drained and evaporated.

So I've abstained from using heat on it at all so far for fear of it being a fire risk, but should I really be that concerned?

Is using a Propane torch liable to cause an explosion if that's the case?

Probably not, but having just gone round with the seized fuel line on my Suburban recently I'd say just go ahead and cut it out now. You'll thank me later.

I've lit that exact same rear brake line on fire on my Rabbit GTI. Panic ensued. Fortunately I was ready for it and I was armed with wet towels and an extinguisher in immediate reach. Towels were all I needed. The better call was to cut the flex line and use a 6 sided deep well socket on it, and on the other side a good flare wrench very slightly pinched by a pair of vise grips. Also, a clay dam around the connection submerging it in PBlaster overnight helps.

Dumb question, but have you tried that 50/50 mix of acetone/atf with the dam idea flogger mentioned?

I had a similar problem with the accumulator fittings on my GLI. I ended up snipping the line and replacing the whole accumulator and stainless hose for peace of mind. Mine was recently wet though so there was absolutely no way in hell I was taking heat to it.

I'll second the idea of cut the line and use a 6pt socket to remove the fitting.

BTDT.

I use torches on brake line fittings regularly. Fire safety gear is always at hand, but I've never had to use it.

I have used heat on fuel line fittings, only after thoroughly purging line, and no where near the tank or other fuel system parts. it's not something that I'm comfortable with, and definitely a last resort.

Heat on brake lines - OK.
Heat on on fuel lines - great way to burn a shop down.

If they are this far gone I would gut the car and replace everything if its a keeper. Its actually shockingly easy and relatively cheap to run new lines, and nothing is worse than a few hours of struggle every 3 weeks because you didnt just swap out everything.

The "vice grips on a flare wrench" is a neat tip. I will try that some time.

Apply heat to a fuel line.. . . . ... It must be safe I googled it for images of a huge fire ball and a burning car and there were non on the first page so this means it is perfectly safe.. . .. Or all the people that did it are dead.

I guess that I should have added that when I'm doing heat on fuel system parts, the parts are usually in a vise on a work bench. Most often I'm trying to retrieve a brass or stainless fitting, stuck in an aluiminum or cast iron part, that can't easily be replaced.

Yeah, I use heat on brake lines no worries.

When any fittings are really stuck though I usually have better luck with vice grips than flare nut wrenches.

Brake lines: Cut the line and put a socket on the nut.

If you're trying to SAVE the hardline, for whatever unfathomable reason, unthread the hose from the hardline. If you heat the hardline with the flex hose attached, the rubber will explode. It's awesome (goes off like a really big firecracker) but stinky. With the hose off, you just get the nut orange and try to move it.

Fuel lines - I have known people who had me hold a fire extinguisher ready while they torched GM fuel filter nuts. I have never had to discharge an extinguisher. However, there are better ways. Cut the line and replace.

To get brake lines loose I heat with a BernzOmatic torch and touch with bees wax, letting it soak in. Then I repeat, any fitting or bleeder will come right off.

I'd cut, install new fittings and flare the line myself. If a fitting won't come off moderately readily, it usually ends up with a mangling or tearing of the line itself. Especially if Mongo put the previous fitting together.

pjbgravely wrote: To get brake lines loose I heat with a BernzOmatic torch and touch with bees wax, letting it soak in. Then I repeat, any fitting or bleeder will come right off.

That I have to try. Just regular bees wax? I know this sounds dumb but where do you purchase it? The only place I see it is in those specialty stores and it has the honey with it.

dean1484 wrote:

pjbgravely wrote: To get brake lines loose I heat with a BernzOmatic torch and touch with bees wax, letting it soak in. Then I repeat, any fitting or bleeder will come right off.

That I have to try. Just regular bees wax? I know this sounds dumb but where do you purchase it? The only place I see it is in those specialty stores and it has the honey with it.

Hardware stores. It's toilet bowl seals.

dean1484 wrote: Apply heat to a fuel line.. . . . ... It must be safe I googled it for images of a huge fire ball and a burning car and there were non on the first page so this means it is perfectly safe.. . .. Or all the people that did it are dead.

Maybe they just couldn't get a good angle to film themselves. Unlike this guy with Miata flambe' : https://m.youtube.com/watch?v=2RBRCaVjYrM

The clay dam idea is an awesome one, though!

dean1484 wrote: ow this sounds dumb but where do you purchase it? The only place I see it is in those specialty stores and it has the honey with it.

I have lots of it because we used to be bee keepers. I believe it can't be paraffin because that is a petroleum product and it can ruin the rubber parts of the brake system. I will have to check the toilet seal lead in case I run out someday.

Don't need bees-wax. Birthday candle works just as well.

I have had it work and not work.

flogger wrote: I've lit that exact same rear brake line on fire on my Rabbit GTI. Panic ensued. Fortunately I was ready for it and I was armed with wet towels and an extinguisher in immediate reach. Towels were all I needed. The better call was to cut the flex line and use a 6 sided deep well socket on it, and on the other side a good flare wrench very slightly pinched by a pair of vise grips. Also, a clay dam around the connection submerging it in PBlaster overnight helps.

The clay dam sounds interesting. Can you explain the process behind this?

WonkoTheSane wrote: Dumb question, but have you tried that 50/50 mix of acetone/atf with the dam idea flogger mentioned?

I tried the acetone/atf mix early on but it didn't seem to budge.

pointofdeparture wrote: I had a similar problem with the accumulator fittings on my GLI. I ended up snipping the line and replacing the whole accumulator and stainless hose for peace of mind. Mine was recently wet though so there was absolutely no way in hell I was taking heat to it.

The most frustrating part is I have a BRAND NEW Accumulator and a better braided line ready to go on it! If I can get this fitting off without replacing the line I'd consider that to be a major victory.

An empty gas tank with vapors is the one that goes boom. The tank full of fuel has no air,for the air fuel spark thing to work. the dripping fluid will flare up ( at least with brake lines/power steering lines).

I would be somewhat tempted to use a heat gun/hair dryer, if none of the sane options like cut the line, or vice grips and a cheater bar worked.

Contradiction wrote: I tried the acetone/atf mix early on but it didn't seem to budge.

Ah, that's my go-to :( If that doesn't work, the next step in the "loosening fasteners" ladder is the angle grinder for me.

Tap on the connection with a hammer, hard enough to peen it a little.