Also look up the temperature gauge mod. Unlike in old Mercedes, the temp gauge in the dash has a control board that creates a dead spot at the "normal" temperature range, to avoid complaints from silly people about engine temp varying with load. That board sometimes fails in a way that has the gauge read hot when the engine is running at safe temp. You can solder in a wire and remove the board to get a correctly-reading gauge without damping.

https://www.brickboard.com/RWD/volvo/1172774/220/240/260/280/replace_compensation_board_jumper.html