Hi. My S60 just had problems today. It was quite dangerous. When I was driving on the rode and trying to reduce the speed, suddenly I found the break pedal became firm and I could not stop the vehicle in a short time. That nearly caused an accident today. After I pulled over and stepped on the pedal several times, the break recovered. Does anyone know what the problem is please? I really do not want this to happen again. I did some homework my own that some peaple said it might be the defects of the master cylinder and some said it might be due to air existing in break fluids. Hope to get help from you soon.

Thanks

 

If the pedal was firm then it is a brake booster issue. The brake vacuum pump might have an issue.