I bought my S80 back in August (first time Volvo owner)
with 207,000 miles on it ,
It has the 2.9 liter twin turbo...
I decided to go ahead and replace the timing belt ,belt tensioner ,water pump,
and idler pulley ...
My dad said I coul've let it go for awhile but figured 1. he's old school
when most engines used timing chains.. 2 it's better to be safe than sorry
and end up with a unpleasant surprise .....

here are the pictures I took...

if I'm not mistaken the idler looks worn and older than the tensioner

 

I think the interval is 110,000 miles for belt change. It was probably done once at about 110,000. It would have been fine for a while, but was getting close enough to another 110,000 miles that doing it was not a bad idea. A lot of manufacturers are going back to chains so your Dad will be new school.

 

2.8 liter

 

Owner's manual says 2.9 liter ,and VIN matches up for that engine
And from research finding out that it's better to do the belt replacement at 75,000
miles.....

 

2.9 liter doesn't have turbos

 

There is a 2.9 twin-turbo

The B6294T is a 2.9 L (2,922 cc) straight-six. Bore is 83 mm (3.3 in) and stroke is 90 mm (3.5 in) with a compression ratio of 8.5:1. It is twin-turbocharged and intercooled with a power output of 272 PS (200 kW; 268 hp) at 5200 rpm with 380 N·m (280 lb·ft) of torque at 1800–5000 rpm. It features dual VVT.

Applications:
2003[160]–2006[70] Volvo S80 badged as S80 T6[70]
2003–2006 Volvo XC90 badged as XC90 T6

 

Thought it was a P2 chassis, nevermind.

 

105,000 or 10 years per Volvo

Service Manager Bulletin 21-044

Engine Code/MY
Engine Version
Replacement Mileage
Vehicle and Regulatory Description Notes
91
B6294T
105,000 miles / 10 years w tensioner & idler pulley

 

It is a P2 Chassis through 2006