Last time I drove the car (1979 model)about a week ago I didn't notice anything different about the brakes--have been pretty weak since I got the car about 8 months back. When I started it today the engine ran very rough and I immediately realized that the brake petal did not feel right. The pedal would go to the floor and the brakes barely worked at all. I checked the fluid and it was still full but I noticed a large vacuum line near the large "canister" had come open (it had been plugged with a screw when I got the car--I had noticed the screw in the end of the vacuum line when I would look for the oil dip stick) I put another screw into the vacuum line (this is a vacuum line that is bigger than the other ones that connect to a plastic air line "manifold" located between the plugged end and the "canister").
Once the line was plugged the engine runs very smooth again but the brakes are only a little bit better. Still practically no brakes---I notice a sound now when I depress the brake petal--it sounds like a plunger moving inside a hand air pump--I'm not sure if it is air escaping or just the sound of something sliding along a surface???anyway, I never heard this before until now.
I'm obviously pretty dumb on brake issues. Any advice on this would be appreciated. I'll probably be seeing a brake specialist soon but the brakes need to be a bit better before I would want to drive it to the shop.

Still love this car though, even with a few problems. I've never had a car before that generates so many comments and looks from others.

Thanks for any help,
79vetteguy (Louis from Mississippi)

It sounds like you need a new vacuum hose for your power brakes. That canister is the brake booster, and you may need a new one of those, too. The hose routes from the back base of the carb to the booster. The booster supplies power to the brakes, so if you have a vacuum leak there, you may not be getting enough "push" on the plunger for the master cylinder. There is a check valve in the hose that is supposed to only allow for airflow in one direction so that all the vacuum is supplied to the brake booster.

Clear as mud??

Add to that there could also be air in the brake lines, which would cause the brake pedal to be soft as well. Even if the power booster isn't working the pedal should still be solid.

Thanks guys for the response---this "check valve" in the vaccuum line---can you see it from outside the line or is it fully inside???Where is it normally located relative to the "brake booster"??? What is really strange is the sound I hear when in the car and I depress the brake petal--it sounds like sometning sliding against another surface, The sound starts as soon as the petal begins to move downward and continues until the petal stops (near the floor)--any idea what could cause such a sound?? seems to be coming from behind dash near firewall???
The brake booster definately lost all vaccuum when the line became unplugged but now that I plugged the line back shouldn't the booster return to normal operation???
Can it be damaged by a temporary loss of vaccuum???

I plan to gravity bleed the brakes this weekend and flush system if necessary to see if this helps--I'll also look for any signs of leaks. Last resort I'll get brakes overhauled and plan to have the caliper pistons with o-rings put in based on what I have read in the other threads on brake problems.

Any other thoughts on this problem would be appreciated.

Thanks

sounds like big problems,aint gonna be cheap,sounds like the booster is shot,there is a big vacuum line that comes off the manifold and goes directly to the booster and plugs into a big plastic fitting that then plugs into the booster that is the check valve. the sound your hearing is probably from inside the booster ,the diaphram is broked loose and sliding around inside.just like an air pump ,you can change the booster yourself,if you dont know enough about brakes let a pro handle it, life is a terrible thing to waste LOL. Ron 78

Thanks Ron,
I'll get it checked out soon.
Thanks again.
Louis from Mississippi