Brake strength

I recently got this car from my dad and i've been trying to get it working smoothly, but the one major problem left is the brakes. When you hit the brakes, there is an extreme lack of pressure. It's unsafe to drive on a normal basis as you can't drive it past ~40 until you know you just won't stop quickly if there were to be an emergency. Could this be caused by simply having air in the lines? or is this this something more serious, like a problem with the master cylinder?
Incase it matters: 92 oldsmobile cutlass supreme sedan, 3.1L

a few things could cause that, but air in the lines is definately one of them. When you say pressure, are you referring to how hard you have to press on the brakes to get the car to stop, or are you saying that the pedal travels to the floor with little or no resistance?

Manny Boy is correct that there are several items that can cause the problem. As he indicated air in the lines is one, bad master cylinder is another. I would also look at the vacuum booster on the brakes. If it is bad it will not provide you boost and you will have a feeling of no brakes, however, the pedal will be hard to push not soft. Finally, check and make sure that the rotors and drums are the proper thickness. If they are too thin the brakes will heat up quickly and you will lose a lot of breaking power. Hope this helps.

I have a 92 Olds Cutlass Ciera S. My problem was a cracked brake line and it was slowly but surely bleeding the brakes. Check for wear particularly near the front side of the rear tires.

The braking FEELS normal (there is a normal amout of feedback) you just have to stand on them for them to be effective

That sounds like a bad vacuum brake booster.

Brakes are far from my specialty. Is the vacuum booster difficult to repair? I try to avoid brakework if I can and leave it to experienced mechanics. If I should try to do repairs myself, what should I look for first?

Is your ABS light on?
When mine was bad, I could pull the vacuum hose off the brake booster while the motor was idling and the idle speed didn't change but when I put my thumb over the vacuum line, the motor slowed down alot. That told me there was one big leak in the booster and it wasn't helping me with my brake effort.
Don't play with brakes, they have to work every time you call on them.

Not really. You will need to remove the master cylinder from the front of the booster, unbolt it from the firewall and remove the pedal activator from inside the car. Some of the newer ones take a special tool. I recommend you get a repair manual as they usually spell it out in detail.

ABS light isn't on. Thanks for the tips! if anybody knows anything that might help me at all please email me ([email protected]) or post. I've already got two service manuals, i'll look through them and see if I see anything that might help more.

that also may be due to the horrible design of the rear brakes for gm w-body cars between 1990-95. With out proper preventive maintenance, the rear sliders freeze, and the rear pads no longer contact the rotor surface, leaving the all the stopping to the front brakes.

that also may be due to the horrible design of the rear brakes for gm w-body cars between 1990-95. With out proper preventive maintenance, the rear sliders freeze, and the rear pads no longer contact the rotor surface, leaving the all the stopping to the front brakes.
is there anyway to fix that problem...the pads not catching the rotors? I have that issue...

Yep, the permanent fix is to upgrade your rear calipers with the calipers from '96+ cutlass, lumina, or monte carlo. the other fix is first ensure your rear sliders are operating, If they are not a small brake hone, can clean them up really quickly, and always lube your sliders with brake grease. Once you have the sliders working, apply your parking brake once a week, it causes the rear pads to adjust. If your parking brake is stuck like most of the earlier w-bodies, then manually pump your rear parking break lever with a pair of water pump pliers, ever so often.

Well, the vacuum booster seems to be OK, so i'm going to see if bleeding the brakes, etc. will fix the problem.

So you're saying when you unplugged the vacuum line from the brake booster, there was a sound of air rushing and the engine speed increased?

Yes.
I pulled the car foward a few inches in the driveway not but five minutes ago, and once I put it in park the car's abs light came on. I put it back in drive then back into park, and then the abs light started blinking. When I restarted the car, the abs light did not come on. Something tells me this is either a fluke or expensive.

Check your manuals for instructions on how to get ABS trouble codes. The places to jumper on the Diagnostic Port of a '92 Bravada is the top right and the bottom, 2nd from the LEFT then turn the keyswitch on. The ABS and BRAKE lights should come on for a coupla seconds then go off. At this point the jumper can be removed and a scan tool be connected to get the trouble codes. Do they apply to a '92 Cutlass? I don't know but it might.
Many Bravada ABS troubles can be traced to the wheel sensors but I really can't see them as making for a hard, unresponsive brake pedal.
I wish I could be more help to you.

The ABS system doesn't seem to want to hold codes. Ever since then it hasn't come on. I'm hoping to gather the rest of the tools I need to replace the system fluid saturday. I'll post then; hopefully that will be the problem.