Among the three Volvos I find myself around (and now possibly a fourth),
the biggest noise items I found were:

Exhaust
Fuel pump
Piston slap / rod knock
Valve noise

The exhaust is the biggest one. My sedan has a fairly rust, one muffler
system. Extremely loud and obnoxious. My wagon, whose timing is more or
less stuck at 20deg BTDC, is significantly quieter because more of the OEM
exhaust system is intact. I'm sure verifying the timing will help some,
but I doubt it will cure any diesel-like noise.

The fuel pump is also a source of some noise, on my sedan it's not even
musical. It's just REALLY loud. On my wagon, it'll get scratchy below
half a tank, and on the friend's (hopefully) new wagon, it's a faint
humming, but it is noticible.

The piston slap I've only heard on the friend's 764T. Genearlly any
thrashed B230 made before 89 or 90 will have it. This means the turbos
are noisier, but not necesarily the only ones. This is what makes his car
sound like a diesel at any temperature. It's noisier than a late model VW
TDI, but otherwise pretty quiet for a diesel as the joke goes. Short of a
rebuild with the pistons that have skirts, there's nothing you can do.
You can of course play around with different oils, which may help some.

The other real big noise I had on my sedan was a clicking noise, kinda a
valve noise. Valves could be out of adjustment, exhaust manifold gaskets
could be gone, and/or the valve dampers could be in poor shape. This
didn't result in a diesel like noise, but a constant clicking. When I
pulled the head I had the valves ground and adjusted, and I used new
exhaust manifold gaskets. Very quiet now (except for the exhaust noise).

The other stuff listed (mechanical fan and accessory bushings) will
contribute to a general noisy feeling, but didn't really leave me with an
impression of my cars sounding like a diesel. Only the friend's B230 did
that for me so far. If you are going to replace the accessory bushings,
which isn't a bad idea, go for the polyurethane replacements. Nick at FCP
Groton has them for about the same price that you'd pay a dealer for new
rubber ones. IPD, and (probably) RPR also carry them.

- alex

'85 244 Turbo
'84 245 Turbo