brake line fitting leak

[John G.]

After installing new flexible brake line hoses front and rear on my '64 and bleeding the system of air everything seemed ready to go when I finally got a hard pedal. .. A check of the brake fluid level in the master cylinder several days later revealed a LOW fluid condition? ..

Turns out both rear flexible hoses had a leak at the at the same flare nut/hard line fitting connection. One leak was fixed by tightening the hard line flare nut fitting just a smidge more. The other leaky side flare nut fitting connection was already fairly well tightened down. A tad more flare nut tightening didn't do anything to stem the leak. It's about as tight as it's going to go, IMO.

Is it ok to 'lap in' the flare nut seat and flared pipe end using valve lapping compound to effect a better seat seal? .. Has anyone done this? ..

John

[mike cobine]

Re: brake line fitting leak

Do you have the regular soft steel lines or the stainless steel lines? The stainless are harder and have been known to have such problems occasionally because the seat won't mold to the other.

If you have a flare kit, try reshaping the flare slightly with it. It could be the shape is slightly kinked or nicked and isn't smooth.

I'd avoid any compound unless you can flush that line thoroughly.

[Duke W.]

Re: brake line fitting leak

There is often a slight geometry difference when you combine new and old flare fitting parts due to one already being formed to its previous mate. I find they will seal more reliably if you tighten - loosen, tighten - loosen - at least three times as this will help form the male and female portions to each other to create a tight seal.

The same can be said for new male and female parts. "Forming" them to each other by multiple tightenings should yield a good seal.

Applying more torque to an already tightend B-nut that has a slight leak runs a risk of striping the thread due to excess torque. Repeated tightening to the proper torque will essentially "tool" the male and female parts to each other.

Duke

[John G.]

Re: brake line fitting leak

Mike ..
Yes, I forgot to add - the short hard line that goes along the trailing arm is the original factory soft steel type. I felt there was no need to replace it as it and the attendant flare nut fittings were still in very good condition. Before I broke out the tube flaring kit I tried Duke's method first . .

Duke ..
Your suggestion did the trick! .. The final tightening of the flare nut into its seat mate felt more uniform, too. No leaks! . .

Thanks for the replies . .

John

[John D.]

Re: brake line fitting leak

Loctite makes a hydraulic sealant that when properly used is wonderful stuff. I use it on various places on the fuel injections. Loctite #545 is available from Travers Tool or other industrial tool catalogs. It is not typically available at auto part stores. Use it sparingly and apply it with a q-tip. One of my friends used SS brake lines on his '67 and had several leaks. We used #545 on the ferrel end of the fitting. Be very careful not to get any into the lines. That was over 10 years ago and still no leaks. Cost is about $28.00 for a small bottle.

[Duke W.]

Re: brake line fitting leak

That's a good reason to use OE type plated mild steel lines rather than stainless. Given the typical service that restored cars see, common plated mild steel brake tubing will probably last at least 50 years, maybe a hundred.

For sure if people don't change the brake fluid every couple of years the lines on a restored car are more likely to corrode from the inside out. Any water splash on the outside dries quickly once the car is off a wet road, but moisture than gets absorbed into the brake fluid will stay there forever unless the system is flushed periodically with new fluid.

Duke

[Wayne C.]

Re: brake line fitting leak

I'm a bit surprised that someone doesn't make copper washers to overcome these bad hydraulic connection seats, such as the problems with stainless lines.

[Clem Z.]

try mc master carr catalog as they did have

copper washers for kerotest fitting. i still have some left over from years ago as i used them mostly on fuel lines to get a good seal