C5 Noob with some brake issues.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 132
Likes: 0
From: Portland Oregon
C5 Noob with some brake issues.
If the car is running and I press the brake pedal everything seems normal until the pedal gets towards the end of it travel, at which point it begins to make some noise like it's venting air down at the pedal. Is this normal? I'm having some break issues and I'm wondering if it's realted.
The problem I'm having when braking is as I begin to press more firmly on the pedal, the pedal always feels quite firm, put as I press harder, it seems to have less braking force. It's as if the brake assist goes out so it momentarily have less clamping force, and then I have to press really hard, and it seems to bite. It's definately not due to heat as it happens at low speed when cold as well as from higher speeds. I recently put stainless lines and higher temp fluid, then bled the brakes and the feel exactally the same. I also replaced the pads just to be sure it wasn't that the pads had been cooked and were no longer any good. The old pads looked fine really.
Any ideas?
PS I'm scheduled to be at the speedway tomorrow
and I haven't been able to figure out what the problem is so I'm a bit aprehensive. 
Thanks
Josh
The problem I'm having when braking is as I begin to press more firmly on the pedal, the pedal always feels quite firm, put as I press harder, it seems to have less braking force. It's as if the brake assist goes out so it momentarily have less clamping force, and then I have to press really hard, and it seems to bite. It's definately not due to heat as it happens at low speed when cold as well as from higher speeds. I recently put stainless lines and higher temp fluid, then bled the brakes and the feel exactally the same. I also replaced the pads just to be sure it wasn't that the pads had been cooked and were no longer any good. The old pads looked fine really.
Any ideas?
PS I'm scheduled to be at the speedway tomorrow
and I haven't been able to figure out what the problem is so I'm a bit aprehensive. Thanks
Josh
Burning Brakes
Joined: Dec 2004
Posts: 1,234
Likes: 2
From: New Jersey
Sounds like the booster is leaking internally.
From what you've described it sounds like your vacuum port is not sealing all the way through the pedal travel.
If the vacuum port doesn't seal then when you apply the brakes air will be pulled into the front chamber causing "hard pedal."
If the atmospheric port leaks then air will be pulled in constantly causing "self actuation" or "soft pedal."
Both will make hissing or wooshing sounds.
FYI: This is not the Vette booster, but they all operate basically the same.
From what you've described it sounds like your vacuum port is not sealing all the way through the pedal travel.
If the vacuum port doesn't seal then when you apply the brakes air will be pulled into the front chamber causing "hard pedal."
If the atmospheric port leaks then air will be pulled in constantly causing "self actuation" or "soft pedal."
Both will make hissing or wooshing sounds.
FYI: This is not the Vette booster, but they all operate basically the same.
Last edited by Mighty-Mouse; Mar 11, 2005 at 06:01 PM.
Burning Brakes
Joined: Dec 2004
Posts: 1,234
Likes: 2
From: New Jersey
I should add:
A soft whooshing sound is normal to hear when you first apply the pedal. That's air rushing into the booster.
Most people never notice it because it is so soft, until you mention it to them then they listen for it and hear it all the time.
You can do a simple test:
1. Turn on the engine
2. Let idle for a minute
3. Turn off engine
4. Apply the brakes, pedal to the floor at a moderate rate
You should get at least 2 pumps from the pedal before it goes rock-hard.
2nd test:
1. With the engine running
2. Apply brake pedal to the half way of it's travel and hold
3. If leaking the pedal will become harder and harder to hold
Repeat the 2nd test but with the pedal to the floor.
Of course this is WITH OUT THE CAR MOVING.
A soft whooshing sound is normal to hear when you first apply the pedal. That's air rushing into the booster.
Most people never notice it because it is so soft, until you mention it to them then they listen for it and hear it all the time.
You can do a simple test:
1. Turn on the engine
2. Let idle for a minute
3. Turn off engine
4. Apply the brakes, pedal to the floor at a moderate rate
You should get at least 2 pumps from the pedal before it goes rock-hard.
2nd test:
1. With the engine running
2. Apply brake pedal to the half way of it's travel and hold
3. If leaking the pedal will become harder and harder to hold
Repeat the 2nd test but with the pedal to the floor.
Of course this is WITH OUT THE CAR MOVING.
Last edited by Mighty-Mouse; Mar 11, 2005 at 06:05 PM.
