Need a Brake Line Guru

[MGD72Monte]

OK, maybe just someone that knows more than me. Incidently I know this is not on suspensions but I did not know where to run this thread.

 

I replaced the rear rubber flex hose and all steel brake lines on the diff as part of a rear end refurb. As soon as I put brake fluid in there I had leaks at every fitting except one. I managed to tighten the leaks away except for the one between the main line coming from the front and the flex hose. I tried everything I could think of, removing, retorquing, checking threads. Other than adding an extension to my line wrench to get more torque (not realistic) I couldn't think of what else to do so I removed the new flex line. The flare on the steel line looks good by the way and it was sealing fine with the old flex line.

 

Here is a pick of the old flex line on the left and new one on the right.

 

 

The new one has a larger inner opening and correspondingly wider taper which likely means less contact with the flare to seal? Otherwise, I have no clue what is going on. I'm thinking of trying the old flex line tomorrow. I don't remember having this trouble when I did the front. Everything seemed to go in without having to call in a wrestler to torque the lines down.

 

Any ideas?

[Sam (Bones)]

I would point my finger at the steel line flare first, a bad flare is normally the cause

[jim's 70]

[stangeba]

I'm remembering a problem like this and it involved metric parts.

Not clear on the details but it was a 1957 Mercedes Benz. The SAE replacement lines almost worked but leaked. They looked the same to the eye. Good luck and let us know where NOT to get the flex line from.

[MGD72Monte]

I would point my finger at the steel line flare first, a bad flare is normally the cause

 

Thanks, I'll guess I have to digest that. The flare looks good to me and that is the existing line that held onto the old hose without leak for 20+ years. I'll have another look at it tomorrow. My thought was to go for the last part changed but maybe I need to rethink or maybe take up knitting instead.

 

 

Originally Posted By: stangeba

I'm remembering a problem like this and it involved metric parts.

Not clear on the details but it was a 1957 Mercedes Benz. The SAE replacement lines almost worked but leaked. They looked the same to the eye. Good luck and let us know where NOT to get the flex line from.

 

Well I'd doubt it is a metric issue or the other two fittings would also leak. Thanks for the encouragement, I'll let you know how it turns out.

[LS5]

..hmmmm. unless it's my eyes here besides the Seat and Larger Flare as you have mentioned, Does it look like the Thread Pitch is Slightly larger in Diameter ??? Causeing the leak. almost like haveing to put Plumbers tape on the Male end and thread that new line on to make up the thickness difference ?? I know it sounds silly but it looks ever so slightly larger in diameter... Failing that the Wrestleing idea still comes to mind as a Good "Figure Four" lock my do it or an "Arm Bar" hold might work....LOL..!!!

Darren.

[Mikstudie]

First thing I would do is get another flex line and see if it is different. I have seen this many times,eliminate the most logical cause before starting to pull your hair out. It's a aftermarket part this happens all the time.

 

If that doesn't work get a brass male/female adapter, screw the adapter into the hose and the steel line in the other end of adapter. Brass is very soft and forgiving and genrally has a larger male flare surface. I have used this method on many applications.

[cny first gen 71]

If it an aftermarket part made in china its just different enough to not work properly.

[MGD72Monte]

Well, after that frustrating experience, and a series of straight days working on the Monte I did not get back to it today, I needed to take a break and do something else... and let my hair grow back.

 

Thanks for all your thoughts and informative points, I'm hoping I can get to the bottom of this.

[MGD72Monte]

Well today was another day and after some procrastination, I decided to go back into the abyss and try again to resolve that leaking brake line. This time I tried to use the old flex line, filled the system and found that, although improved, the static leak was still there despite some agressive torquing. So I drained the rear portion of the system yet again (an uncomfortable mess every time) and decided to cut the steel line and reflare it (thank God there was sufficient extra line to do so). I also went to the store and picked up a new flare nut as the old one was starting to look a little tired of being muscled.

 

After some uncomfortable under the car flaring (twice) and rebending the line it seems to finally be sealing! at least statically. I now have to find time to remove the master cylinder and bench bleed it to get the air out and confirm it can stand the full pressure.

 

Here is a pic of the flare I cut off. The only slight defect I can see is at the 3 o'clock position but how the heck did it manage to seal for 20+ years. The shop that installed it must have had a gorilla on staff to torque it down .

 

 

Thanks again for the inputs, good diagnosis Sam and Jim, I definetly did not think the existing flare was the problem. Another lesson learned the long way.