Rear brake line developed a leak. can i just replace the small broken section or do i need to replace the whole line?

You may only need to replace a section instead of the whole thing. I took mine to my repair shop and they fabricated a piece to fit the rear section that was rusted through. They cut the old line where it was solid forward and coupled the two together. The rear is easy to get to. If you replace the whole line all the way to where it goes forward, it takes a lot and is pricey for the hours they have to put in.

Most likely you have a cylinder in the rear leaking, and it's just slinging it off as you go. Your van should have front disc brakes and rear drum. Cylinders are normally $10 to $20 each. Wouldn't hurt to inspect both

Did you get a good bleed with fluid coming out at all four wheels? If they bled good, and the pedal still goes to the floor, you need to check the brake master cylinder-it is probably shot with an internal leak. An internal leak will not let fluid pressure build up, so no brakes.

Did you keep the brake fluid reservoir from going dry while bleeding? If it went real low, air might have got back into the lines.

It is not uncommon when bleeding brakes on an older vehicle for the master cylinder to suddenly develop an internal leak and require replacement . Here's why: pushing the pedal all the way to the floor causes the master's piston to push in farther than ever before. The rubber cups then travel over a section of the cylinder not usually touched by the cups-old fluid can develop a crud there and when the piston pushes over it, the cups can get ruined. To avoid this when bleeding brakes, put a short piece of 2X4 wood block under the pedal. Then the pedal will not extend the master's piston beyond it's normal travel. Of course on a new master cylinder, you do not have to do this. A new master cylinder does require bench bleeding before installing, however, to ensure no air pockets develop from there.

The front reservoir (the small one)is for the rear brakes.Have you pulled the rear brake drums and checked the wheel cylinders for leaks?
Is the rubber seal on the reservoir cap in place?
Follow the lines carefully to the rear brake hose and on the axle to the brake cylinders too.
Lastly,it can be leaking from the front section of the master cyl internally to the rear section of the master cyl but not likely.

is the metal line or the rubber line leaking? if its the rubber hose just get a new one at the local parts store they are specific to your vehicle.
if its the metal line buy a roll of tubing if you want to replace the whole line dont forget the correct fittings. if you just want to repair a section get a piece of line apx 2 ft longer then the section you want to repair with the correct fittings and that will cover it. Best repair replace the whole line do not patch or will end up repairing it again down the road.

If it is the rubber line attaching to the caliper, you need to replace the short rubber hose. The hoses do wear out over time from all the flexing stress involved. All parts stores sell them.
If the leak is from a steel line, that section of line will have to be replaced. Not likely any GM dealer would still carry a parts line for a discontinued Cutlass, nor would any parts store ever carry brake line sections (except for the rubber hoses). One could find the same section from a salvage yard, or have a shop construct the broken section from brake line tubing, with proper fittings at each end.
In most cases, it is the rubber brake hose that develops leaks. So, back to the parts store. When replaced, the brakes will have to be bled, to get trapped air out of the brake lines.

You can replace line in full section or just a piece. Full section would be my suggestion, remove brake line from end to end that is bad..this doesent mean you have to remove the complete line clear up to the front of car,it should be in sections. After removing bad section take it to auto parts store and as the can give you the correct size without guessing. Most sections bought at auto stores are straight and can be bent useing brake line bender.They useually cost around 15 to 20 dollars.....after bending and replacing be sure to bleed brake system.....nedd more help fill free to contact me...good luck

You CANNOT repair a leaky line, I'm afraid. You will need to replace the leaky section. Don;t forget to bleed the brakes afterwards.

Broken brake line or loose fitting OR it can be most likely a faulty whel cylinder

You need to remove it. It can be replaced in sections using couplers but it should not be put together with ferrule type unions. You may need an adapter fitting on the master cylinder. Make sure everything is secure and cannot vibrate. use as many of the factory mounts as possible but you do not need to follow original routing exactly (this stuff is put in really tight sometimes) be careful bending tubing any kinks will result in a restriction or early failure..