How to test all new brake lines and flares with no master cylinder installed

[Brian4618]

I am in the process of restoring a 72 k10, has drums in rear and disc in the front. I was wondering if anyone has a trick to test all the flares I have made, as I bent and flared all the new lines. I would use the brake pedal and fluid to test it, but the cab is still removed.

Thanks, Brian

[NEWFISHER]

Clamp the master to a jig or frame work near where it will normally mount. Install the lines and "bench bleed" the master.

[BR3W CITY]

I've seen fuel lines tested by hooking a union to the brake line then the other end to a air hose fitting and using high pressure air to test the lines that way. I've used it on other things non-automotive as well. Not sure how it would work on brakes with the piston and everything but it tells you if there is a gaping problem pretty quick.

Not sure if you could use compressed air to put pressure on FILLED lines, but it might be possible.

[Snailed]

You need pressure over 1500psi to properly test a brake system...150psi shop air would be just for massive oversights like BR3W said. Your leg and the stock brake pedal with master will probably be the most convenient way to do this.

[ray_mcavoy]

Even though shop air pressure is considerably lower than the brake's normal operating pressure, it does make an excellent way to test newly installed brake lines to see if the flared connections are making a good seal.

I've done it several times and would rather locate a leak using air instead of having brake fluid weeping out of a connection and dripping onto a freshly painted frame/chassis.

I just pressurize the empty brake lines/system by connecting shop air to the line(s) that would normally connect to the master cylinder. Then I spray all of the connection points with soapy water and watch for bubbles. It doesn't take much to cause a leak with flared fittings where the seal is made by the metal-to-metal contact between the flared end of the line and the seat. It's often just a matter of tightening the nut a little more to stop the leak. And it's real easy to see that it's tight enough when the soapy water stops bubbling.