Pedal goes to the floor

[kkingsrulee]

I drove my '90 RS 305 TBI for the first time in about four months yesterday, it fired up fine, and ran great, but there is a severe problem with the brakes. I topped off the brake fluid before I started it up, yet the pedal (after the car is running) goes all the way to the floor, it's impossible to build up pressure, even though the reservoir is full. Any ideas? The pedal literally goes all the way to the floor and you can feel it hit the floorboard upon braking. Thanks for any help.

[1ADan]

have you tried bleeding the system yet? may want to try that first before anything else. pull the tires, check for leaks and check hoses for any kind of cracking.

no leaks, and all bled, may have an issue with the vacuum booster

[kkingsrulee]

I'll check the lines and bleed them maybe on monday when I have time. But how could there be a vacuum booster problem? Too much boost? That just doesn't make sense, there obviously is no lack of "boost". Two possible theories I am backing are that there is just a HUGE amount of air in the system (The car sat for about two-three months without any fluid in the reservoir). Or that there is some sort of blockage that is preventing the fluid traveling from either the reservoir to the master cylinder or from the master cylinder to the calipers, I'm thinking the latter. Any suggestions are greatly appreciated.

[1ADan]

the booster idea was a bit out there, but i have heard of times where people have had "mysterious" loss of fluid without visible leaks; turns out the fluid was leaking into the booster. rare, but can happen. only came to mind since you said you had to add a bit of fluid to top off the reservoir.

[kkingsrulee]

I've heard of this, but you can usually tell because the fluid escapes through the bottom of the booster by the firewall and you can see the paint bubbled and ruined because the brake fluid leaked down the firewall.