hi all - having some issues with my '90 740 turbo wagon not heating up in the colder weather - engine starts and runs fine, fuel consumption remains around 25mpg highway (330k km) but the engine does not seem to be warming up as much as she usually does - in warmer weather temp gauge is pretty much vertical, now it sits about 1/4 (45 degrees from vertical) and only creeps up a little more when not driving on the highway - last winter she seemed to pump out a lot more heat and warmed up a lot faster, where should i start my troubleshooting? or should i just resign myself to the fact that she is getting older?