The front passenger flex hose on my new (to me) 2003 Blazer 2 door 4x4 was frayed so I replaced it today. I did this same job on my old Jimmy, so I wasn't expecting any issues. Not the case unfortunately.

I could not figure out why the brake pedal was going almost to the floor after repeated bleeding. Turns out that there was fluid leaking from where the metal line joins the flex hose. I tried tightening the nut more, but when the truck is running and the pedal is applied a small amount of fluid can be seen around the exposed threads on the brake line. So I'm not sure what happened. Cross threading maybe? I was really careful to prevent this when I first attached the hose, but I don't know what else it could be. To make matters worse, the nut on the brake line is starting to round off (yes I used a flare nut wrench) from all the tightening/loosening.

I gave up for the night since I ran out of brake fluid, but if it turns out that it is cross threaded, do I have to replace the entire line? Any other reason besides cross threading that it would leak? I'm not familiar with brake lines, but googling around it seems that you can't just buy a replacement.

I was really expecting this reapair to take an hour tops.

 

Worse case you can cut the line..get a new coupler and re flare the line if it is cross threaded
some parts stores have the flaring tools in the loan a tool system...its double flared though

 

Did ya replace the copper crush washers?

 

If you can get the line back off, clean the threads off with brake cleaner and look at them, might have been rust or dirt on them happened to me before. If the threads are all tore up you can join a peice of line in or just replace that line to the master cylinder whatever you find easier to do.

 

Yeah, that's not where it's leaking from. It's a very small leak where the flex hose joins the hard line.

I took everything apart again and looked at the threads on the flare nut. They looked okay, maybe a little worn on the first thread or two. When tightening the nut there is a little resistance at first, but then turns easily, so it doesn't seem to be cross threaded. Those first couple of threads might be causing the problem I guess.

I put everything back together, and attempted to bleed the brakes again and to see how much it was leaking. This time the leak wasn't as bad, but now I could see that not only is it leaking past the threads, but seems to be leaking up between the nut and the brake pipe and out the top of the nut. Could this mean that the flare is compromised? I drove it around a little and it seems to stop okay, though the pedal seems a little more soft than it was before I attempted this repair. There is still a very small leak, I could tell since I placed a paper towel around the connection and it was a little bit wet.

I am most likely going to say screw it and bring it to a shop. I don't trust my flaring abilities if that's what needs to be done. I was hoping that there would be a way for me to repair it as is, but looking around here and the 'net it seems that it's not possible (thread tape, thread sealant, etc not a good idea/wont work). Thanks for the responses guys.

Edit: Is there supposed to be any sort of o-ring or gasket in the fitting for the flex hose to the hard line? Just want to make sure it isn't something simple. I compared the old hose to the new and I don't see any o ring on the old hose, but I thought I'd check to be sure.

 

No O ring or seal of any kind, just an inverted flare fitting. It's possible the steel line rusted to the flare nut and when you loosened it, the steel line cracked. If that's the case, the only "fix" is re-flare the end, (which would be difficult due to the short 90 degree bend at the end). Or go back to the next junction and replace the entire line.

 

i do all the brake lines at my work and wouldnt even bother re-flairing the old line and would just replace it, usually way easier, ive only flaired inside a car a few times, usually only if there is a good enough section of line to do it and enough room to work in there.

shop should probably charge under 100 bucks for that.

but yeah that light should just tighten and not leak, since its already possibly cross threaded go ahead and grab some vise grips and see if it will snug up anymore

 

I took the truck to the shop down the street the other day to have them look at the leak. According to them, the fitting was "loose" and all they did was tighten it, bled the brakes, and it was okay after that. No more leak. I really don't get WTF happened. I tightened the crap out of that flare nut, so much so that it was starting to round off even using a flare nut wrench. According to Alldata, you're only supposed to tighten it to 13 ft/lbs. The guy at the shop said something about "$300 set of wrenches" that they used, so maybe they just know how to tighten a nut better than I do? Who knows. I've checked it every day and no leak so far. Weird.

 

My guess would be a set of Snap on line wrenches. Good quality tools do make a difference. Anyway, glad you get her fixed, and thanks for posting back.

 

If it's an after market or generic hose the flaring may not match up. Best bet is to cut off and go with a bubble flare. Thats becoming more standard.