Why don't brake lines need gaskets?

[bdcardinal]

High pressure fuel line connections on 30,000+ psi diesel fuel systems are metal on metal. Sometimes can be a pain to seal up if there are any imperfections on the mating surfaces.

Yup, I keep all the fuel injector lines for the 6.4 and 6.7 Ford diesels in stock because they are not supposed to be re-used. Same as the common high pressure lines on the EcoBoost engines. People get irrationally angry having to buy extra parts, but when the shop manual says it must be replaced, its not like they have a valid argument.

 

[blupupher]

Still metal to metal.


Water pumps, exhaust manifolds, oil pans. Their gaskets are failure points but they still use them.

Those all have large contact areas with partial sealing areas.
A brake line has 1 very small point of contact with all the clamping force from the 1 nut in the 1 spot.

Think of a 1/4 inch hole in the side of a metal water tank.
Try stopping the flow of water with the palm of your hand, then your thumb. Which works better?

Plus with the flare, the metal pieces form a much better seal than the "flat" seal of the ones you listed.

 

[chrlsful]

low pressure + small (so strong in metalurgy terms) ?
All of us, almost, R using judgment terms (low/hi, tight/loose).
I have no concept the mathmatical terms (how much psi, tq)) but
they can help define for better understanding.
I thought it was just the flair'n the tightening (I really crank...
50, 60 ft lbs?)

 

[PF52]

They had Morton-Thiokol design some special o-rings.

It'll be fine! It's not January.

 

[Astro14]

low pressure + small (so strong in metalurgy terms) ?
All of us, almost, R using judgment terms (low/hi, tight/loose).
I have no concept the mathmatical terms (how much psi, tq)) but
they can help define for better understanding.
I thought it was just the flair'n the tightening (I really crank...
50, 60 ft lbs?)

Brake line fittings take just a few ft lbs. That is all that’s needed to seal them properly.

If you think that you’re tightening them to 50, 60 ft lbs, either you have no idea how much torque that is, or you’re buggering them up. They will strip out long before 50.

 

[Yah-Tah-Hey]

Brake line fittings take just a few ft lbs. That is all that’s needed to seal them properly.

If you think that you’re tightening them to 50, 60 ft lbs, either you have no idea how much torque that is, or you’re buggering them up. They will strip out long before 50.

I replaced all the brake hoses on my 04 Camry a year ago. I think the torque value was something like 14 ft. lbs

 

[Chris142]

Still metal to metal.


Water pumps, exhaust manifolds, oil pans. Their gaskets are failure points but they still use them.

They don't have 1000 psi behind them.

 

[tnt_motorsports]

As others have said it is the flare or double flare of the design. It is like JIC (37 deg flare) fittings for hydraulics. There is no gasket there it's metal on metal sealing.

Just my $0.02

 

[chrlsful]

^^X 2
dont havea tq wrench in my wrist like some. I use such ona lug wrench "clicker' (I set asian/lill guys at ~80/90, p/u trucks at 120/50).
A lill different (flat metal to flat) but my DD has no gasket at the oil pump p/u tube to pump mating.