Brake woes.

September 26, 2006 6:52 AM

I'm having an extremely weird brake problem with my '94 Grand Am.

Alright, so for the past couple of weeks, my car's brakes have been acting funky. Just about 15 minutes ago, when pulling out of the gas station, I depressed the brake pedal, and it *started* off well, then all of a sudden, the pedal gave. Immediately, I pressed it even more (almost to the floor), and my car stopped fine (albeit a little erratically). The brakes themselves aren't making any noise, so I wouldn't think it has anything to do w/ the pads/rotors/calipers.

Also, something I didn't even think of (then again, I'm not that car savvy) that could be a problem: low brake fluid?

I'm sorry if my problem seems to be very broad and undetailed, but like I said, I don't know a whole lot about cars, and this situation has been hard to duplicate. I'd like to get a smattering of possibilities as to why my car's doing this before I have a mechanic drive around for an hour to try and get the problem to come up.

Thanks.

posted by booticon to Travel & Transportation (11 answers total)

it could be air in the brake lines ... leaking brake lines ... a brake cylinder that's going ... low brake fluid ... and although it might not be the pads/rotors/calipers that's causing this, it's quite likely that those are worn down pretty well, too

a mechanic probably won't drive it around to find out but just look at the brake system

my guess? ... you have substantial brake repairs to do
posted by pyramid termite at 7:00 AM on September 26, 2006

Response by poster: Hm, I just checked the brake fluid, and that's fine, so I think I'm going to bring it in tomorrow. What do you think the avg. cost for brake-line replacement is (ball-park figure)?
posted by booticon at 7:19 AM on September 26, 2006

Do you have antilock brakes? I had a 90 Buick which was the same as a 90 Grand AM and my brakes exhibited a similiar problem. It turned out to be a problem with the pump in the ABS controller and would have been very expensive to repair.

Otherwise a bad seal in your master cylinder can cause this problem. A rebuilt unit is often 100-200 and it takes a couple hours to Re&Re plus bleed all the lines.
posted by Mitheral at 7:26 AM on September 26, 2006

What do you think the avg. cost for brake-line replacement is (ball-park figure)?

not familiar with a 94 grand am, but this probably depends to a large degree on the competency of the mechanic and the design of the engine bay / brake line routing.

the parts are not particularly expensive (they're just some metal tubes, probably something like $80-$120 for enough to replace the whole car's worth). however depending on the way the brake system was engineered the new lines can be a real bitch to remove (and more so to put in!)

i've done this once before (on a 96 neon) and it took me a couple hours to remove one line, a couple more to replace. a real mechanic would probably be much faster and have some clever tricks, but if the car has some unfortunate engineering choices it might still take a while. so labor's going to be the major part of your cost.

you could simply have some air in your lines, in which case simply bleeding the brakes might fix your problem. shouldn't take more than an hour to do.
posted by sergeant sandwich at 7:43 AM on September 26, 2006

That exact scenario just happened to me two weeks ago -- it turned out to be bad brake cylinders, which was about, oh, a billion dollars (or $900 at the dealer, OUCH) to repair.

Can you stop driving it and get it towed to a shop? I just had a flashback freakout for you. Be careful.
posted by kittyb at 8:04 AM on September 26, 2006

I'm almost certain that you've got a brake master cylinder that's gone kaput. If you've got intermittent pressure, as well as low brake fluid, it means the fluid is going somewhere. Usually it's leaking past the seal in the master cylinder, which also means you're losing pressure in the system. That's why you're having trouble slowing the car.
posted by ninjew at 8:47 AM on September 26, 2006

i had the exact same problem with a subaru with anti lock brakes. to make it drivable, i removed the fuse that powered the abs system.

it really pissed me off when the subaru mechanic told me that it was stupid to do so, and that the car was perfectly safe. yeah, moron, you're not the one driving it.
posted by lester's sock puppet at 9:13 AM on September 26, 2006

This sounds like a master cylinder to me too. Usually you can do a test without moving. Start your car and keep it in park. Press on the brake and hold it. If you foot slowly sinks to the floor, that's the master cylinder.

The master cylinder is the device that provides the "power" in power brakes. It does this with vacuum from the engine. The usual failure is a vacuum leak. They aren't too expensive and labor should be only an hour.
posted by kc0dxh at 9:33 AM on September 26, 2006

If your break pedal is dropping and the fluid level is remaining the same then the seals inside the master cylinder around the plunger are leaking. You will not see this leak as the fluid is being redirected back into the reservoir. You need a new master cylinder.
posted by Paleoindian at 10:44 AM on September 26, 2006

Paleoindian nailed it. Fortunately, the brake master cylinder in this car was used in many GM cars. You can pick one up at Auto Zone and put it in yourself with a little chutzpah and a Haynes guide.
posted by M.C. Lo-Carb! at 3:26 PM on September 26, 2006

I also was thinking this sounds like the master cylinder or power break booster. IANAM, but that's where I would start.
posted by jxpx777 at 10:54 PM on September 26, 2006