Omg...help

1969 Stang · 03-27-2002, 10:50 PM

First my brakes a sort of new...front disc rear drum...now the brake pedal has to be almost all the way down for me to stop at a stop sign or stop light...and so on...now when I push the pedal even a little bit I hear a hisss sound...kind of like when you let out the air in a coke bottle slow...what could be the problem...Its scary to drive my car...and now its going to rain...if no one knows just pray...thanks.

PKRWUD · 03-28-2002, 10:44 AM

Sounds like two different problems.

Do you have power brakes? The noise you described sounds alot like a power brake power booster with a torn diaphram. However, when this occurs, the brake pedal tends to become hard, and excessive effort is needed to stop the car.

As far the pedal travel is concerned, if you converted your car to front disc brakes, but did not also replace the master cylinder with one for a disc brake car, you will have a problem like you described.

Take care,
-Chris

Clark Rodgers · 03-28-2002, 12:24 PM

This is exactly what happened to mine and the booster should be the cause of the air leak and make sure you have the correct master cylinder with the two different size reservoirs.

Try and give us some more details like did this just start? What work did you have done? Does the pedal get better if you pump it?

Gearhead999 · 03-28-2002, 09:22 PM

Sounds like it needs a booster. Send it to Booster Dewey and have it rebuilt.

66StangGuy · 03-30-2002, 04:05 AM

sounds like you have air in the line. bleed the brakes and see if that helps. i replaced the brakes in my 66 recently and needed to bleed the brakes. even if you didnt change the brakes you could have run low on brake fluid and ended up putting air into the line. Easy thing to check at least. i had the hissing sound too. if i pressed the brake slowly it seemd to have no sound but if i press it somewhat fast there would be a hiss.

mustangman65_79 · 03-30-2002, 05:06 AM

If u bleed the brakes, and it still does the same, it's the brake master Cyl. Only about $30. I think it will be just that, a new master cyl. My bronco did the same thing when I replaced my brakes. When a master cyl gets worn, along twith the old brakes, it will still work, but when U replace the brakes, the master cyl is now having pressure build up when is wasen't used to having it. What is happening is the pressure of the fluid is bypassing through the seals, back into your Resivor. Also, you'll notice that your new brakes will wear faster then before. This is because the fluid that is bypassing the seals, is making backpressure, so when U let off the brakes, the back pressure will make the brakes rub harder then normal. Making abnormal wear. Hope this helps.

1969 Stang · 03-31-2002, 09:59 PM

update:
went to my uncles friends place...He said I may need a electric vacuum pump or something like that...I have a very mild cam in the beast. Now the master cly. has recently been replaced. I haven't tried bleeding the brakes YET. Now the pedal has changed some I push it in about 1-3 inchs. and it hisses. and from there on get ready to stand on the brakes to stop that thing. It is very hard...The did a test on the vacuum at the brake booster took off a hose. The test is as followed.
at idle 500-600RPM. 10 psi of vacuum. at about 3kRPM it was at 40psi. So does that help anyone...I don't know anymore...
p.s. thanks for all the help.

Rev · 03-31-2002, 10:09 PM

If the pedal goes down deep near the floor, then it is a hydraulic leak for sure or low fluid level. Might be in the master cylinder (new or not) or could be anywhere else in the system (lines, wheel cylinders, or front calipers).

Don't drive it like that. Find the problem and fix it.

Rev

Clark Rodgers · 04-01-2002, 11:20 AM

I guess I am missing something here, if your brake booster goes out what happens? I know when mine has happened the brakes almost go to the floor but work with some extra effort. This sound familiar?

You do bring up a good point about the vacuum that's why I was asking did this just happen or was it after a cam change? or some other maintenance?

PKRWUD · 04-01-2002, 11:19 PM

Your update supplies the answers, and confirms my first reply.

You haven't bled the brakes since replacing the master cylinder. Bleed them.

The pedal becomes rock hard when you hear the hissing. There is a leak in the booster diaphram. Ever notice how hard the pedal becomes when the engine is shut off in a car with power brakes? That's because vacuum is no longer being applied to the booster. The hissing you are hearing is the vacuum escaping from the booster, and the hard pedal is the result. The Power Brake Booster needs to be replaced.

First replace the booster, then bleed the brakes. All will be well.

Trust me.

Take care,
-Chris

Rev · 04-06-2002, 03:14 PM

My bet is that is was a bad master cylider. So what was it?

Rev

03-27-2002, 10:50 PM	#1
1969 Stang Registered Member Join Date: Dec 2001 Location: Pomona, CA Posts: 93	Omg...help First my brakes a sort of new...front disc rear drum...now the brake pedal has to be almost all the way down for me to stop at a stop sign or stop light...and so on...now when I push the pedal even a little bit I hear a hisss sound...kind of like when you let out the air in a coke bottle slow...what could be the problem...Its scary to drive my car...and now its going to rain...if no one knows just pray...thanks. __________________ Go Ahead.... Unleash your beast.... Mine will be waiting.... Ricer Hater's Club - Member #37

03-28-2002, 10:44 AM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Sounds like two different problems. Do you have power brakes? The noise you described sounds alot like a power brake power booster with a torn diaphram. However, when this occurs, the brake pedal tends to become hard, and excessive effort is needed to stop the car. As far the pedal travel is concerned, if you converted your car to front disc brakes, but did not also replace the master cylinder with one for a disc brake car, you will have a problem like you described. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

03-28-2002, 12:24 PM	#3
Clark Rodgers Registered Member Join Date: May 1999 Location: Rowlett,Texas Posts: 306	This is exactly what happened to mine and the booster should be the cause of the air leak and make sure you have the correct master cylinder with the two different size reservoirs. Try and give us some more details like did this just start? What work did you have done? Does the pedal get better if you pump it? __________________ 69 393W Sportsroof deluxe

03-28-2002, 09:22 PM	#4
Gearhead999 Registered Member Join Date: Sep 1998 Location: Oviedo, FL Posts: 992	Sounds like it needs a booster. Send it to Booster Dewey and have it rebuilt. __________________ "Support our Troops" Dave 1968 Cougar 2004 Thunderbird 2007 F150 Harley-Davidson, SuperCrew 1986 LTD 1997 Ranger 1992 Honda Civic

03-30-2002, 04:05 AM	#5
66StangGuy Registered Member Join Date: Feb 2002 Location: Diamond Bar Posts: 258	sounds like you have air in the line. bleed the brakes and see if that helps. i replaced the brakes in my 66 recently and needed to bleed the brakes. even if you didnt change the brakes you could have run low on brake fluid and ended up putting air into the line. Easy thing to check at least. i had the hissing sound too. if i pressed the brake slowly it seemd to have no sound but if i press it somewhat fast there would be a hiss. __________________ 66 mustang-292-Holley 4160-World Castings Windsor Sr.-Hooker super comp headers-MSD box & Coil.3.55 gears. B&M Z-Gate-Black leather racing seats with 4pt harnes.

03-30-2002, 05:06 AM	#6
mustangman65_79 My poor 79 RIP Join Date: Oct 2001 Location: Suisun City, Posts: 2,320	If u bleed the brakes, and it still does the same, it's the brake master Cyl. Only about $30. I think it will be just that, a new master cyl. My bronco did the same thing when I replaced my brakes. When a master cyl gets worn, along twith the old brakes, it will still work, but when U replace the brakes, the master cyl is now having pressure build up when is wasen't used to having it. What is happening is the pressure of the fluid is bypassing through the seals, back into your Resivor. Also, you'll notice that your new brakes will wear faster then before. This is because the fluid that is bypassing the seals, is making backpressure, so when U let off the brakes, the back pressure will make the brakes rub harder then normal. Making abnormal wear. Hope this helps. __________________ '84 mustang GT turbo '85 LTD '89 Camaro Irocz z28 '94 Lightning '96 Trans am

03-31-2002, 09:59 PM	#7
1969 Stang Registered Member Join Date: Dec 2001 Location: Pomona, CA Posts: 93	update: went to my uncles friends place...He said I may need a electric vacuum pump or something like that...I have a very mild cam in the beast. Now the master cly. has recently been replaced. I haven't tried bleeding the brakes YET. Now the pedal has changed some I push it in about 1-3 inchs. and it hisses. and from there on get ready to stand on the brakes to stop that thing. It is very hard...The did a test on the vacuum at the brake booster took off a hose. The test is as followed. at idle 500-600RPM. 10 psi of vacuum. at about 3kRPM it was at 40psi. So does that help anyone...I don't know anymore... p.s. thanks for all the help. __________________ Go Ahead.... Unleash your beast.... Mine will be waiting.... Ricer Hater's Club - Member #37

03-31-2002, 10:09 PM	#8
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	If the pedal goes down deep near the floor, then it is a hydraulic leak for sure or low fluid level. Might be in the master cylinder (new or not) or could be anywhere else in the system (lines, wheel cylinders, or front calipers). Don't drive it like that. Find the problem and fix it. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

04-01-2002, 11:20 AM	#9
Clark Rodgers Registered Member Join Date: May 1999 Location: Rowlett,Texas Posts: 306	I guess I am missing something here, if your brake booster goes out what happens? I know when mine has happened the brakes almost go to the floor but work with some extra effort. This sound familiar? You do bring up a good point about the vacuum that's why I was asking did this just happen or was it after a cam change? or some other maintenance? __________________ 69 393W Sportsroof deluxe

04-01-2002, 11:19 PM	#10
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Your update supplies the answers, and confirms my first reply. You haven't bled the brakes since replacing the master cylinder. Bleed them. The pedal becomes rock hard when you hear the hissing. There is a leak in the booster diaphram. Ever notice how hard the pedal becomes when the engine is shut off in a car with power brakes? That's because vacuum is no longer being applied to the booster. The hissing you are hearing is the vacuum escaping from the booster, and the hard pedal is the result. The Power Brake Booster needs to be replaced. First replace the booster, then bleed the brakes. All will be well. Trust me. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

04-06-2002, 03:14 PM	#11
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	My bet is that is was a bad master cylider. So what was it? Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe