Hello,

Hope someone can help me out. I have a Volvo S80 V8 of 2007 (185.000 km), which was always maintained by Volvo. Last week I had a sudden loss of brake power being able to push the pedal to the floor with no resistance at all. It happend 2 times at very low speeds and with turned wheels manouvring in and out a parking lot. I am getting afraid that it may also happen at higher speeds.... The Volvo garage cannot find any clue as the diagnostic system reports to be healthy. No leaks, no fluid loss, air or whatever. During failure no warning lights popped up. After the incidents the car drives and brakes perfect. When will be the next time? I think this is surely a safety issue for Volvo and it should not be allowed to happen. Who can help me?

 

That is a traditional failure mode for the master cylinder itself on any car. They use soft seals, and if once it doesn't seal, then you would replace it.

 

were you able to pump the brakes back to pressure? - if you have an internal seal problem in the master, ie loss of pressure without an external leak, I'd think you should be able to pump up pressure. Given it seems to correct itself, I'd also be suspicious of the ABS controller and its valves, or perhaps a fault in the brake pedal position sensor (which I'd think the Volvo tech would be able to test). Considering the severity of the safety issue, I'd go back to the Volvo dealer and talk to the service manager about getting some master technician help from Volvo corporate if need be. Also - did you get any braking action? Another common fault is a loss of vacuum boost at first start up after the car's been sitting overnight due to a failed check valve or vacuum pump. In that case, you'd have to press really hard on the pedal to get any braking action but once you drive the car (say 100 feet) the engine produces enough vacuum to return the feel to normal.