I just bought a 2004 S40. It has 35,000 miles on it. I have noticed that when I first start the car and just move it about a cars length, the brakes are not working properly. They feel like the old standard brakes, with no power assist. Like the power brakes is not working. Most "power" brakes work off a vaccum assist, but it acts like there is no assist. However, by the time I leave the driveway, everything is OK. I'm not sure if it is the vaccum assist not working, the anti-lock circut not working, or if it is a normal thing. I read in the manual that the car has to get to 4 mph and the abs does a self-test. So, if I move the car a little in the driveway, forward or backwards, the brakes are hard and you have to push on the pedal as hard as you can.
What do you think?
du907

The car has an electric brake booster pump. When you start the car pump the brake pedal you should hear an electric motor kick on and off with a humming sound. It sounds to me like the pump is probably not working.

Also when you first start the car the engine vacuum is very low because the turbo spins when the engine is cold. On cold start-up my turbo gauge shows only about 5 pounds of vacuum and I can hear my brake pump kick on every time i hit the brakes. Thats why I am sure that the pump is your problem.

Thanks for your reply.

I checked the pump. I disconnected the pumps electrical connection and applied 12V from the battery. The pump ran making that humming/buzzing sound you mentioned. Also, when I took the power away from the pump, I could hear the backflow valve click. I then took out the relay and check it with a meter and voltage and it is working. I also checked the fuse, and it is also good.
For some reason, the circut to the vacuum pump is not completing and the pump is not coming on.
du907