Reading many posts about replacing brake lines/MC/hose, etc. and not much mention about the torque required to make a solid fitting connection. I've just replaced much of my brake system and several connections are leaking... front banjo bolts as well (I'm suspect that the banjo leaks are due to thin copper crush washers)

The Good Book says fitting connections should only be around 20 ft/lbs... but I'm finding that grossly inadequate for a good seal

Experience would tell me that over tightening can distort the conical sealing surface... any experience share would be helpful!

Cheers!

 

I don't recall ever seeing a torque spec (I'm sure there is one). I have installed dozens of brake lines and calipers and wheel cylinders over the years, and never used a torque wrench once. It's really all about "feel" which comes from experience (the experience of breaking bolts and striping threads).

But to your question -
well, you tighten it enough that it doesn't leak and not so much that you break the fitting or strip the threads.

 

lol... advice to live by
Im not using a torque wrench either... I can just tell that I'm beyond 20 lbs. I'm also using the "feel" mode... but seems that I'm having to tighten the fittings more than I "should" based on how the seal is made.

I was surprised how tight the fittings were when I was disassembling the system... but it had also been sitting for 15 years... so... rust.

 

Are you using a new copper washer?
I believe an old washer that has been used or tightened before is harder to seal because the soft copper sealing-face has now been "crushed" which then requires a lot more torque to get a good seal.
Those crush washers usually have a raised sealing surface (like small circular raised lines) that do the actual sealing.

 

The flare has to conform to the fitting, that's what makes the seal. One technique that seems to work, is to tighten the fitting, then back off and tighten it again. And again.

 

This post is just to make visible what Tedster has to say.

 

In my experience if you flare your own lines, they tend to need more torque to quit leaking. The factory flared lines seem to seal a little better.

Just keep tightening them till they quit leaking. You can damage the cone in the fitting, nothing you can do about it but replace whatever it's mounted in. I don't know if you can still buy the new cones or not.

 

All good information, I also go by feel and go as tight as needed to make a seal.
I have seen it posted if you make your own flares when you make the 2nd part of the flare don't go real tight on the die.
The reason is the flare get too tight and has no "crush" left in it to seal.
Just something to think about.


The other thing is SS brake lines. SS is harder and does not have the give for the crush and you really need to crank down on the fittings.
Dave ----

 

thx all... all good advice... and pretty much what I'm finding... just wanted to see if I was having an abnormal experience

FF2: I agree with your comment re not cranking down on self-made double flares... That is most likely the reason I'm having issues. If the cone is too "wide/deep" there's no opportunity for the the sealing function of the fitting. Steel lines are a PITA to flare. I had better results not "over prepping" the line for flaring. I found that if you use a standard tube cutting tool, the end is pretty much ready for flaring... with only minor chamfering required.

I'm using new crush washers... the ones that came with the new flex-hose... but they're much thinner than the originals. I didn't think to check that before I installed all the new stuff. On the caliper sealing side, the washer sits in a shallow recess... if the washer is too thin, the banjo fitting will start to seal against the uneven surface of the caliper casting making for a bad seal. I'll need to replace those.

 

You should have 2 washers, 1 for each side of the hose fitting.


As for steel lines and making your own there is a copper/nickel line, has a grayish color to the out side, you can buy in coils.
It is easy to flare and bend if you need to run the line thru out the car/truck.
Dave ----

 

If I can help it( I usually can) I don't flare the lines at all, I use the pre-flared lines they have hanging in the store. They usually end up a little bit long, so I make a extra curve here and there to take that up. The only time I have to flare a line is when the factory used a odd-ball sized nut like on the master cylinder connections.

 

- Fedhill