Brake pedal stiff at startup

[Boardin_ut]

I have read several other threads and none of them seem to match my issue. If there is one alread I apologize. Just point me to it and I will move my question over to it.

My daughter has a 2005 Aveo. Occasionally, and not every day, when the car is started the brake pedal will barley budge and you have to put all your weight into it to press the pedal. If you continue to drive like that, the pedal and brakes seem to return to normal. Typically once the car has been driven, the issue does not resurface again until it has sat for a few hours or overnight

We also found that if you start the car and we do not move it, then turnn the engine off and then back on again - sometimes it'll take two or three attempts - then brakes work like they should. I took it to the dealer and since I had driven it the problem did not reproduce itsself for the technician.

I am about to take it to the dealer and leave it with them for a few days in hopes it will act up on them at some point. I am hoping that a few of the more savvy mechanics in the forum may be able to provide some suggestions, ideas, or may have heard of this one before. Thanks for looking.

[Daox]

This all has to do with vacuum and the brake booster. As soon as the engine starts up you should have vacuum in the brake booster to make everything feel normal. If there is a leak in the booster the pedal will get hard. It will also get hard if you pump it a few times when the engine is off.

[Boardin_ut]

@Daox:

Thank you very much for taking the time to reply. I had read a thread with an issue similar to mine. I decided to take a chance and replace the brake booster. The problem seems to be fixed so yuor advice is spot on. It does appear to be a leak in the booster.

Appreciate it and have a good weekend.

[rickprado]

This all has to do with vacuum and the brake booster. As soon as the engine starts up you should have vacuum in the brake booster to make everything feel normal. If there is a leak in the booster the pedal will get hard. It will also get hard if you pump it a few times when the engine is off.

Hello, great forum. I recently bought a 2005 and had the exact issue. Spurned like a typical booster problem. I went ahead and replaced it and master cylinder with new OEM unit. 3 days ans almost 500 later, the issue has retuned, I almost rear ended someone today. Same as before.

Any more ideas where to look?