Check the harmonic balancer to make sure it is not slipping. Does the steering effort increase? Is your engine running hotter? Is the AC not running very efficiently? These are all examples of loss of belt drive/friction which is a classic sign of harmonic balancer failure. You might not know if the steering effort is increased since the car is so new, but the other signs might be there.

Use some white-out and paint a white line from the outer metal grooves of the harmonic balancer, across the rubber insert, to the center of the harmonic balancer where it is bolted to the crankshaft. Drive the car around for a while... then see if there is a break in the line. If so, you've got a bad harmonic balancer. Rule this out before diving down any more rabbit holes--it's an easy diagnostic step to take, and a common problem in 20+ year old Volvos still running on their original harmonic balancers.

The issue is the rubber insert, which degrades with age. Degradation may be advanced by a "heat event" such as a cooling system failure which heats up the engine significantly. New HBs are about $200 OEM from the dealer, or about $50 from FCPGroton (but questionable MTC part).

You're going through the exact same problems I faced this past fall, and it turned out to be the harmonic balancer (after new alternator/volt regulator/wiring harness/battery/etc).

kourt
87 245
austin, tx