Lately, when I cruise down a hill and lightly apply the brakes, the pedal sinks a bit lower than normal and the "BRAKE FAILURE" light illuminates. However, the brakes are fine if I apply the pressure quickly or pump the brakes several times.

Also, when the car is idling and I hit the brakes, the engine RPM drops. The lights also dim a little. I suspect this is an alternator issue, because this also happens when I roll 2 or more windows up at a time. Can anyone help me with these issues? Thanks!
Josh

 

Likely a brake master cylinder failure. If it's original I would replace it as well as the brake junction box (octopus). At least it should be diagnosed by a brake man, preferably an independent Volvo mech. Brake fluid (DOT4) should be replaced every two years, and changing the brake fluid can sometimes make a significant improvement. But the "brake" light indicates the switch in the junction box has been tripped. I would have it replaced. I would not do it myself because there's too many brake lines to mess up unless you have experience.

Post back.

 

I've got a '90 240dl and the brake fail light was intermittent. Brought to my mech and the light went away, but so did my brakes. Any ideas? PLEASE HELP!!!

 

He might have just killed the bulb? 1. First check for any leaks 2. Flush and fill with the correct order, if you do not do it properly will not work. Instructions are on forum or in Bentley Book. Next if still no brakes replace master cylinder...repeat flush to get any new air out that you've introduced to the system.