2005 V70 D5 manual transmission, 135k miles: With ignition off, car in gear and handbrake disengaged, the brake pedal feels hard, with very little travel. On turning on ignition (clutch pedal down) the brake pedal feels soft, with a lot of travel, although the brakes do work OK. What could be the possible/likely reasons for this behaviour please?
Many thanks.

 

Possibly a vacuum leak in the power brake system. Vacuum makes the pedal feel softer, the vacuum helps push the pedal down. If the pedal is hard the vacuum has leaked out or you used it pushing the brake pedal with the engine off.

Am unfamiliar with diesel - does it have an electric or mechanical vacuum pump? Either way it appears to be working. (pedal gets soft after starting)

Try turning off the car with your foot on the brake - if the pedal pushes back up - you have a quick vacuum leak. You should be able to stop the car normally a few times after the vacuum pump stops, unless you have a leak. Could be a check valve, a hose or even the booster.

 

Thank you for these suggestions. I will investigate further.