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Topic: Pedal goes to the floor, hissing sound (Read 9502 times) previous topic - next topic

Pedal goes to the floor, hissing sound

Some guy in a Taurus pulled out of his driveway in front of me and I had to lock it up to keep from hitting him. The car stopped fine, so I continued on my way to the gym. On the way back it was fine...until I was stopped at a red light. Then out of the blue the pedal goes all the way to the floor, and I hear a hissing sound when I hit the brake pedal. The brakes barely slowed the car down, and I had to drive home in low gear and pump the brakes to get anything out of them. The brake light stayed off. What do you think? Bad brake booster? If so, any recommendations on a replacement? I figure that a stock one for an '87 5.0 would be unobtainable today, but I could be wrong...

Edit: talked to my neighbor of 30 years who is also our mechanic. He's going to see if he can fix it tomorrow...here's hoping he can get what he needs...
[SIGPIC][/SIGPIC]
5.0L Speed density
Explorer intake
'92 Mustang GT cam
GT-40 racing heads
Unequal length headers
Custom-made duals
19# injectors
65mm TB
AFPR
T/C header panel
11" brake upgrade
T/C rear sway bar
Electrical mods: too many to list :D

Pedal goes to the floor, hissing sound

Reply #1 –
My first guess would be booster too, but check your fluid level. If you push really hard with a bad booster, you should still have brakes although the pedal may seems so hard to push you think not.
Check for a popped rubber line in front or rear too.

Pedal goes to the floor, hissing sound

Reply #2 –
Yeah, he mentioned the fluid too, that it could be a leak. I told him to check everything. The sick part is that Saturday I was going to head to NJ for a 11" brake upgrade courtesy of Sick88Tbird. Hopefully I can still make it :disappoin
[SIGPIC][/SIGPIC]
5.0L Speed density
Explorer intake
'92 Mustang GT cam
GT-40 racing heads
Unequal length headers
Custom-made duals
19# injectors
65mm TB
AFPR
T/C header panel
11" brake upgrade
T/C rear sway bar
Electrical mods: too many to list :D

Pedal goes to the floor, hissing sound

Reply #3 –
its the booster.. my 83 did it when I got it... its not fun jamming your foot under the pedal doing 45 down a busy road because if you let off you're going to lock up...
One 88

Pedal goes to the floor, hissing sound

Reply #4 –
Yup break booster. Had it happen when I got the car out this year. Leaving work hit the brakes at the intersection and it didn't do anything. Sounds like a snake under the dash.

Pedal goes to the floor, hissing sound

Reply #5 –
Hmm.. I actually read your post this time.  It sounds like you have a fluid issue of some sort.  A booster will not keep your brakes from working if you can push the pedal down.  A bad booster will either not want to go down (no vacuum, diaphragm busted, super hard pedal) or it will want to stay down, as so in my case. 

You hearing a hissing noise is probably exposing a hole in the diaphragm by having to push the pedal down further.

Your booster is bad (not the cause of your failing brakes) and you have a leak somewhere.  I would start at the rear end checking the wheel cylinders, they are usually the oldest part as no one pays attention to them.  They tend to lay dormant near failing until excessive pressure is applied to them, I've blown out a few in extreme braking situations.
One 88

Pedal goes to the floor, hissing sound

Reply #6 –
When wheel cylinders fail that dramatically, it's usually easy to tell...the inner sidewall of the tire will usually be soaked with fluid.  Like you said John, when it rains, it pours...we'll get to that 11" brake conversion when we get to it...don't stress yourself out over it.

Good luck,
Don
Project 3G: Grandpa Grocery Getter-'85 Crown Vic LTD 2-door, 351W with heavily ported/polished GT40 heads, heavily ported/polished Typhoon Power Plus upper & lower intake, Comp Cams 265DEH retarded 1*, FAST EZ-EFI, HD T5, 8.8" 3.73 trac lock with extra clutches, 3G alt. swap, '99 CVPI front brakes, '09 CVPI rear disc brakes, '00 CVPI booster&m/c + wilwood adj prop valve.

Parted & Gone-'88 T-bird Sport, 351W swap, ported GT40 heads

Pedal goes to the floor, hissing sound

Reply #7 –
like said before, its not limited to the brake booster b/c no booster, like said before wouldnt cause it to go to the floor.  just for kicks take the rear tires off and the drum and inspect the cylnders.  with it going to the floor, your pushing fluid out somewhere.  if you had good brakes and no booster, you'd get a pedal feel as that of manual brakes.

Pedal goes to the floor, hissing sound

Reply #8 –
Hmmm. Yeah, maybe it's both. When I had to jam on the brakes the pedal was REAL hard. It's been like that on and off for a few years, though most of the time the pedal was fine.
[SIGPIC][/SIGPIC]
5.0L Speed density
Explorer intake
'92 Mustang GT cam
GT-40 racing heads
Unequal length headers
Custom-made duals
19# injectors
65mm TB
AFPR
T/C header panel
11" brake upgrade
T/C rear sway bar
Electrical mods: too many to list :D

Pedal goes to the floor, hissing sound

Reply #9 –
If the pedal goes to the floor, it sounds like the MC gave out.

I Had a 85 Mustang GT with bigger rear drums installed and when I tested the car from a 35 mph "brake slam" I heard a loud pop and I had busted the rear rubber brake line. Scared the hell out me.

Pedal went to the floor immediately.
Alan Mackin--Semi Professional Ford der
83 T-Bird 460
83 T-Bird Heritage 5.0
84 T-Bird 5.0
86 T-Bird Turbo Coupe NHRA Stocker & Super Stocker
87 T-Bird Turbo Coupe
88 Bronco II Drag truck 302
95 Mustang GT auto
2004 F-350 CC Dually V-10

Pedal goes to the floor, hissing sound

Reply #10 –
Sorry to jack but I have the same problem, the pedel going to the floor and hissing under dash. I just did the WHOLE rear brake setup including new wheel cylinders, and I'm not leaking any fluid. Would this be the same thing, a bad booster?

Pedal goes to the floor, hissing sound

Reply #11 –
On my 87 sport, I had the same problem, pedal to the floor with the snake, and once my booster was replaced (only the booster) the problem was solved.
Resident "Idiot".

Formerly TBob5pt0 :shoothead


Quote from: JeremyB;165772
Repairing a lock cylinder that is frozen or sans keys requires a drill, gumption, and a midget on a tricycle.
Quote from: Big_D
Forgot to put on intake hose when starting the car, sucked neighbors cat into intake.

Pedal goes to the floor, hissing sound

Reply #12 –
i just hope its not a secondary leak on the primary piston in the master cylinder, but warbird prolly has the fix for ya.  if you notice the rear brakes or front brakes not responding well or weak, it could be the master cylinder.

Pedal goes to the floor, hissing sound

Reply #13 –
Quote
Would this be the same thing, a bad booster?
Generally,

Hissing only while pedal is actually moving down...
- Fluid leak. (pedal drops to floor)
- Booster's foam air filter bad, makes the "normal" sound louder.

Constant hissing, worse when the pedal is held down...
- Bad booster, not sealing internally. (hard to push pedal at all)

Constant hissing, doesn't change with pedal position...
- Leaking cruise control valve or hose. (normal braking)
Death awaits you all with nasty, big, pointy teeth.

1988 5.0 Bird, mostly stock, partly not, now gone to T-Bird heaven.
1990 Volvo 740GL. 114 tire-shredding horsies, baby!

Pedal goes to the floor, hissing sound

Reply #14 –
Constant hissing, worse when the pedal is held down...
- Bad booster, not sealing internally. (hard to push pedal at all)

Sounds about right. Sometimes you hit the brakes there is brakes, sometimes it just hisses and goes to the floor. Fluid level doesn't change, bleed all the brakes and build the rear from scratch. Fronts are soon when I do the 11" brakes.