I want to start off by saying thanks for such a great site. I am experiencing issues with my 03 S60 non-turbo. About 10% of the time the brakes will go alot further than typical and feel spongy. My first gut was that it is a master cylinder fault. Itook it to the dealer that I purchased it from 7 months ago and they suspected air in the lines. Made since to me so I had them flush the system to get air out of the system. It worked great for a day or so. They reccomended a master cylinder for $800+. I am not sure if this is the culprit because of the inconsistency of the problem so I got a second opinion from a non Volvo mechanic. They said the reason for the master cylinder fault was worn pads and rotors. I have had 3 oil changes from the Volvodealer and they said they check the pads and rotors every oil change and that they were fine. My question therefore is would this somehow affect the master cylinder. My pads have about 3/8" left but I can feel that my front rotors are worn about 1/16th of an inch and maybe a 32nd on the back. At this point I am very confused. I don't feel comfortable dropping the $800 for a master cylinder when I have read some posts on here of similar problems in which the master cylinder didn't fix the problem. Thanks in advance.

 

Welcome to the forum.

So am I. How do you know that your rotors are worn by the amounts you quote?

Volvo recommend that pads should be changed when they are down to 3mm. The minimum thickness for the front rotors is 23.0mm but ifnew pads are being fitted the minimum is 23.8mm. The minimum thickness for the rear rotors is 10mm but if new pads are being fitted the minimum is 10.7mm.

I agree about the $800with no guarantee that it will fix the problem but I would recommend that you get the rotors and pads measured accurately.

 

The spongy brake pedal you mention is typically due to air in one or more brake lines. The intermittent 'slipping' brake pedal sounds like a booster or master cylinder issue. I seem to remember a recall or TSB on brake boosters that affected a few different years. (Try searching around a bit...)

If you are seeing 3/8" of pad on your front brakes and your wear is 'normal' your pads/rotors should be fine. Even a completely worn out set of pads will not affect the master cylinder. (I would suspect total BS there ...)