Brass unions in steel brake lines.

[MagicRat]

I have to replace some brake lines on a '97 Jetta. To speed up the job, I plan to use new prefabricated lines (already with flares and fittings).

For the rear, I need 2 lines due to the length. I will have to use a brass union to join the two together.

My question is, in theory, are these unions ideal for brake line use?

I have used them in the past, without a problem, but I seem to recall some mechanics think they are a bit 'mickey-mouse'...

Your thoughts?

[Mavrick14]

Nothing mickey mouse about them, i use them every day. Double check all connections for leaks and you'll be good to go.

[curtis73]

As a rule, they are a no-no, but in practice they seem to do just fine. Under extreme brake pressure (which can exceed 2500 psi) is not enough to burst the fitting, but it can be enough to rip the threads out of the soft brass.

I've used them a lot without issue. I wouldn't call them mickey mouse, but I also wouldn't call them ideal.

[Mavrick14]

Originally Posted by curtis73

As a rule, they are a no-no, but in practice they seem to do just fine. Under extreme brake pressure (which can exceed 2500 psi) is not enough to burst the fitting, but it can be enough to rip the threads out of the soft brass.

I've used them a lot without issue. I wouldn't call them mickey mouse, but I also wouldn't call them ideal.

That's not a valid point. The same fittings joining your unions are used to mate your hard lines to your flex lines, abs units, junction blocks, prop valves etc.

This isn't a "no-no" and there is no rule of thumb not to use them.

[MagicRat]

Originally Posted by Mavrick14

That's not a valid point. The same fittings joining your unions are used to mate your hard lines to your flex lines, abs units, junction blocks, prop valves etc.

This isn't a "no-no" and there is no rule of thumb not to use them.

Upon further investigation, I think it depends on where the union is.

Fittings to flex lines and blocks are often 'out of the way, less likely to be harmed by impacts, flying debris, road hazards, etc. Unions in similar locations are likely fine.

However, it seems like a 'no-no' to use a union where an armored brake line is supposed to be. An armored steel line that gets snagged or hit by something may resist the damage more than the soft threads and fittings of a brass junction.

FWIW, my work on this Jetta must pass a Ministry of Transportation of Ontario (MTO) safety inspection. The inspector says it's okay to use unions, so I'm good to go.

Thank you all for the input.

[curtis73]

Originally Posted by Mavrick14

That's not a valid point. The same fittings joining your unions are used to mate your hard lines to your flex lines, abs units, junction blocks, prop valves etc.

\

This is not correct. The factory as a rule doesn't use brass fittings. There are gold-coated steel fittings that look brass, but the only time a brass fitting is used is on heavy banjo fittings on some rear brakes lines. In those cases they are made of an alloy that looks like brass, but is only about 40% brass. The rest is nickel and steel.

Look closely at factory brake lines. They don't use brass. As a rule, the burst strength of brass is not sufficient in some panic braking situations. Period. I stand by it. Actually, you are right in the most semantic way... its not a rule, its a law. OEMs don't use brass because they can't. The DOT won't let it happen. If the factory put a car on the road with brass brake fittings would be illegal because the DOT forbids it.

In this photo, notice that all of the factory lines have steel fittings. The line-lock installed in the vehicle does not. While not immoral or particularly unsafe, there is a reason why the DOT doesn't allow it.




Now take a look at this photo. I promise you there is not one ounce of brass in this photo. What looks like brass is an irridite coating to prevent corrosion. Many times the OEMs will use other colors for the irriditing to "color code" the sizes, but this IS NOT BRASS.

[Mavrick14]

Yes, factory does not use brass fittings - but we are not the factory. When you replace a broken or rotten brake line on a car with standard fittings, you are likely to be using brass fittings. Therefore, the line you are replacing will have brass fittings mating with your flex lines.

I agree that steel is stronger, but the point i am making is that brass fittings and unions are completely legal and safe.

[curtis73]

Originally Posted by Mavrick14

I agree that steel is stronger, but the point i am making is that brass fittings and unions are completely legal and safe.

Safe, maybe. Legal, not by a long shot. The use of brass is strictly forbidden by FMVSS 106 and 116.

Of course, the EPA also states that you must replace a muffler with a factory replacement instead of a glasspack or flowmaster, but that doesn't mean its enforced.

In many states the use of brass fittings for brake line will be cause for immediate rejection of an inspection sticker because of FMVSS 106.

I'm not saying its unsafe, but according to the law, it is definitely illegal. The only place brass is legal for braking systems is in air brakes. Air brakes only see a maximum of about 150 psi. Hyrdaulic brakes however can easily see 2000 or more psi. As a former engineer for two American car companies and three European marques, I'm very familiar with the MVSS.

[Moppie]

Fortunatly we don't all live in the USA

[Mavrick14]

I dont live in the states either, and as far as i know, there is nothing illegal about brass fittings on brake lines. Like I said, i use them every day on customers cars and I havn't met a tech, including myslef, who wouldnt safety a car because of brass fittings (in Ontario).

[curtis73]

Damn Canadians... you get all the breaks... or "brakes" as the case may be

Again... nothing immoral about it, but its not legal here in the states. Technically the stainless braided AN brake lines aren't legal either since they don't have the FMVSS 106-required "DOT" printed on them, but that isn't to suggest that they aren't safe.

We Americans have a HUGE gap between functional and legal, but a narrow gap between legal and moral. No one enforces brass brake fittings, but radar detectors and tinted windows are evidently something that comes directly from hell. We're quick to make laws that ensure safety, but quick to enforce the laws that make money. You can drive a car that might have a brake failure, but if you smoke marijuana, you are suddenly a felonious baby killer or something. I don't get it.