2001 S40 Losing Brake pressure

rhlee222 · Post by **rhlee222** » 02 Oct 2013, 19:29

Hi All,
My son has been driving my S40. He said that for the last several days, when he starts his car, the first time he has to stop, the brakes go to the floor. After he lets up on the brakes, he has pressure for the rest of the trip. Does anyone have any ideas? I can't find info. on this symptom.
Thanks,
Rick

Post by **jimmy57** » 02 Oct 2013, 19:43

That car uses an electric vacuum pump to make sure power brake function works. When the engine is cold it does not make its normal level of vacuum and the pump has to function for it to stop well with normal pedal height. So if the problem is only on a start after engine is off for 8 hours then it may be only failure of the pump or its switch or power circuit.
If he lets the car run 4-5 minutes before he drives off and it does not have the symptoms then that points to the vacuum pump

rhlee222 · Post by **rhlee222** » 05 Oct 2013, 15:41

Thanks for the info. He says it happens when the car sits for a while, happens once, then never happens again, until the car sits for a while. I drove it yesterday after it sat for a few hours and didn't get the symptom.

rhlee222 · Post by **rhlee222** » 13 Oct 2013, 17:50

jimmy57 wrote:That car uses an electric vacuum pump to make sure power brake function works. When the engine is cold it does not make its normal level of vacuum and the pump has to function for it to stop well with normal pedal height. So if the problem is only on a start after engine is off for 8 hours then it may be only failure of the pump or its switch or power circuit.
If he lets the car run 4-5 minutes before he drives off and it does not have the symptoms then that points to the vacuum pump

So far, it doesn't happen after letting the car warm up for a few minutes. Thanks for the info.
I can't seem to find the vacuum pump. can you tell me where it's located?
Thanks,
Rick