View Full Version : Clutch & Brake in - car rolls. Start engine - brakes engage. Why?

05-12-2011, 08:23 PM
My driveway is on an incline. When I go to start my car in the morning, I put my foot on the brake, depress the clutch, and the car starts rolling. Once I start the engine, the brake pedal sinks about an inch and the car stops rolling. The only way to avoid the rolling it is to use my e-brake.

I've bled my brakes but that didn't help. My best guess is the brake booster has a leak so there is no pressure after the car has sat overnight. Anyone have any better ideas before I start throwing parts at this problem?

murdered APR a4
05-12-2011, 08:52 PM
mine does the same thing but it stops fine so im not concerned

J Ozzie
05-12-2011, 10:23 PM
mine doesn't! SUCKAAAAA lol

Keep an eye on your fluid to see if you have a small leak.

05-12-2011, 11:38 PM
Easy way to tell if you're booster is holding vacuum:

Start up car
Run for 30 seconds
Turn off car
Walk away for an hour
Come back
Pump brake pedal

If the brake pedal is easy to push the first time or two but starts to stiffen up, the booster is holding vacuum.

You should have SOME brakes, definately enough to keep from rolling in a driveway, maybe you're not pressing the pedal very hard?

05-13-2011, 12:15 AM
With no vacuum you'll have to really heave down on the pedal to get the car to stop.

Here in the UK we typically use the "e-brake" (or handbrake as its called here) for parking, and for holding the vehicle on hills and inclines and while at junctions etc.

Why is holding the car on the e-brake a problem?

J Ozzie
05-13-2011, 01:24 AM
i always hold the car on the E brake and every time i park it.. E brake up

05-14-2011, 08:18 AM
Thanks for all the input. I generally try to avoid parking with the handbrake on so the pads don't sit in contact with the rotors, especially after some spirited driving. It's not too big a deal to use the handbrake to hold the car when I start it. I just wanted to make sure this wasn't a sign that my booster or master cylinder were on their way out. I'll check for vaccuum and fluid leaks to be safe. Thanks again!

05-14-2011, 12:06 PM
It is the booster that isn't having any vacuum left in the morning. Not a fluid problem. The leak is probably quite small and insignificant. It could be the booster itself is leaking off the vacuum, or it could (more likely) be a leaky check valve or it's vacuum connection (at the firewall or right at the booster).

J Ozzie
05-15-2011, 04:06 AM
listen to Walkie this guy knows his shit!

Check all your lines..

05-15-2011, 05:53 AM
I have a booster available for 50 shipped or 75 shipped if you want a master with it to make it a complete bolt on swap.

05-15-2011, 06:15 PM
the issues is either the brake booster not holding vacuum or the one-way valve going to the booster that isnt holding the vacuum, check both