One problem related to crankcase (pcv) has been reported for the 2004 Volvo S60. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Volvo S60 based on all problems reported for the 2004 S60.
The pcv "flame trap" has clogged in my 2004 Volvo S60 with only 41,000 miles and as it turns out, this is a $1200 job. I wouldn't be so dismayed had I not discovered that this is an extremely prevalent problem and that it is guaranteed to happen to your car prior to 100,000 miles. That there is nearly no amount of maintenance one can do to prevent this problem. The worst part about this problem is that if it's not repaired promptly, it will lead to oil burning and the damaging of various seals in the engine which will lead to catastrophic engine failure. Volvo has extended its warranty coverage for this problem on its s40 model cars which share the engines in the S60, yet has not acknowledged this to be a major problem in its S60 models.