There is a plastic block and two gaskets that go between the fuel pump
and the block. Frequently the plastic block cracks. I'd replace it
if it is cracked, as there seems to be no real repair. Tighten the pump firmly
but not too tight or you'll bend its ears and it will always leak.

You might want to replace the thermostat. Sounds like it might be sticking.
Get a new rubber ring for it also as they get hard and a regular gasket doesn't
work. That might cure the boiling. One thing that makes them run hot is
having the ignition not advanced far enough. I run mine with about 21°
advance (BTDC) with everything connected. Volvos seem to require more advance
than most other cars. On the other hand, if you get pinking or kicking back
against the starter you may have it too far advanced, which can also make
it run too hot.

You don't say what year yours is but if it has the bulb/tube sensor it will
tend to read low rather than high if damaged. Therefore the temp it reads
is probably right. If you have an electric temp gauge that is a different
matter entirely.

If you still have trouble with real overheating in normal operation (NOT
sitting and idling) you might want to check if the internal water tube in
your cylinder head is in the right place and directing flow over the
combustion chamber.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma