In the mornings when the car ('99 C5 Coupe) is cold, the brake pedal goes soft and down to the floor when I first touch it. After that it is fine.

Any ideas???

I had new rotors and pads installed recently - could that have caused something ?

 

Pump up the system and then hold your foot on the pedel for a few minutes. See if if creeps down to the floor. Sounds like your master cylinder might be leaking by.

Bill

 

:o My wife says my original description of the probelm was incorrect...

She says when the car is cold and she begins to back out of the driveway, when she initially steps on the brake pedal it goes down about a half inch and she cant push it any further and the car does not stop -- in about 3 or 4 seconds (about half way down the driveway or time enough to think "oh crap, I have to stop the car") the pedal begins to depress further and the brakes start working. She says this only happens once a day in the morning (and more dramatic when its cold.)

Someone have any idea what to check first?

 

i'm pretty sure there was a tech bulletin about this.the problem is the brake booster or at least it sounds likea booster problem.i will have to check,but i remember reading something about replacing the brake booster for your symptom.
the bulletin i was thinking of was for a 01' for the brake pedal not returning causing the brakes to drag.it's still possible to have a bad booster though[ice/water getting in to the booster/blocking the vacuum passage,etc.].if the problem didn't happen until the brakes were done,i agree,take it back and have it checked

 

Yup, the Calipers/Brake pads are binding up. Take the car back to the shop that did the brakes and have them inspect the brake work they perfomed.

Ask them if they installed the NEW pad retainers that come with the GM pads.

 

They were not GM pads. I will take it in and have them check it all out tomorrow.

 

I agree with the above, this sounds a little like a booster issue, although it doesn't make sense that it just started with the brake work. If the pedal is going down and stopping, but the car is not stopping, something is either preventing the pad from further contacting the rotor (binding), or it is contacting but your wife cannot apply enough pressure to cause the car to stop (i.e. no boost). Without the booster the pedal takes ALOT of pressure to cause the car to slow (try to brake while the car is rolling - turned on but not running - and you'll see what I mean)

In your new description, is your wife applying constant pressure the entire time? Or is she letting up and then repressing?

With the car off:
How does the pedal feel 1st thing in the morning when cold?
Then later when warm (with car turned off)?

If your booster is holding vacuum, the pedal should sink easily the first press, then be very hard after letting it back up and pressing again.

If you do some repeated brake application in the morning when cold, but still in the garage (not moving) do you still experience the same issues when backing out? (i.e. does it only happen the first time the car is rolling and cold)

The reason I have trouble believing it is the pads binding up is because this should happen sporadically, not just the very first press in the morning.

 

Did the people who conducted the brake service, remove the calipers and drain the brake fluid from the reseviour? There could be air in the system. The booster could also be causing the problem. How is the vacuum line and the vacuum fitting on the back of the manifold?



After the car has set for the period of time that the problem occurs, pop off the vacuum fitting out of the brake booster (it should pop out of the gromet easily) and see it you have an inrush of air (vacuum) from the booster reseviour. If not, you have somesort of leak from some where!

BC

 

Took it back to the place that did the work and they removed the calipers and re-bled the brakes. As of today my wife says it is still doing it. I will check what you guys say to check in the next couple posts sometime this week and get back to you.

 

Okay, yes, the pedal sinks easily the first press, then is very hard after letting it back up and pressing again.

With the repeated brake application in the morning when cold, but not moving, we do NOT experience the same issues when backing out!!! (i.e. it only happens the first time the car is rolling and cold and we havent yet touched the brakes.)

Any thoughts now?

 

Try this: With the car OFF, press the brake pedel a few times to pump up the system so that the brakes are tight. With moderate pressure on the pedel, see if the brake pedel sinks to the floor after 4-5 minutes.

Then try the same thing with the car running.

Sounds like the master cylinder could be leaking by internaly. If that is the case, it might need replacing. What type of fluid do you use?

Bill C