Volvo 850 Wagon GLT the power brakes stop working after being driven for an extended period of time. I'm not sure if it is related to driving time or braking time though. I do know that the ABS Wheel Speed Sensor is bad (No speedometer and the odometer stopped counting at 256K), The Computer Cluster is suspect as we are unable to download codes into code reader... it just says "Error" or something along those lines. Could the computer cause the problem or is it a vacuum hose that leaks when the hose expands/contracts from the heat, or would it be the disks overheating and causing problems?