2004 XC90 2.5L High-pitched whine when key turned part way

APCalifornia · Post by **APCalifornia** » 02 Feb 2015, 00:29

Recently have begun hearing a high-pitched whine, like an electric motor on overdrive, as the ignition key gets to position 1. If I leave it there for a minute it stops, but as soon as I start the car it comes back, then it stops for a short while and then comes back. It sounds like a fuel pump motor, but I'm not sure why it would start and stop during driving. Obviously can't hear it very well on our freeways, but driving around town I can.

APCalifornia · Post by **APCalifornia** » 06 Feb 2015, 20:34

OK, thanks to Swedespeed finding a couple of links on what sounded similar. It turns out there have been issues with hoses and a check valve on the brake booster pump getting old. So I followed the noise and found that a tube had become disconnected from the booster. I had done a transmission flush some months ago and probably didn't push the tube onto the connector all the way until the click. It must have worked it's way loose - now it's fixed!