Finally, my '90 240 is nearing roadworthiness again. I have recently replaced the water pump and thermostat, as the old ones were apparently 22-year-old original parts. However, it seems to take nearly 15 minutes before any warm air comes out of the heater and defroster vents, but it's like a sauna when it does. My old '91 240 and '92 740 (love those B230's...) seemed to take a while too, but not this long. Is this "normal" for these 240's? My DD '84 BMW 533i begins to get some warm air within five minutes. Also, the temp gauge needle goes to the upper range of the black very quickly, not typically into the red though. This happens even after running for only a minute or two, well before the radiator hoses begin to feel very warm. If I drive it long enough, it'll settle around the middle. I don't trust that gauge...is this symptomatic of the faulty compensator board I read so much about?

 

Car should warm up within a few miles, maybe 3. Are you letting it sit to warm up or driving? Once almost warm, it should put out heat.

 

I'll only let it sit while idling for 2-3 minutes at most, but usually a minute or two idling first if the engine is totally cold. It may just be coincidental, but slowly sliding the temperature control bar to cold and back to hot seems to help bring heat...but it may just be me.

 

Sounds like you thermostat is stuck open. What brand of thermostat did you use? From what I have read, use a Wahler brand as that is what OEM was. You can check your new thermostat in a pan of water using a thermometer. Heat up the water on the stove and see what temp the thermostat starts to open. It should open at the temp listed for that thermostat.

By the way, what temp thermostat did you buy? I believe that the in the northern climates, they came with a 92 C thermostat. If you live down in warmer climates, an 88 C is recommended.

I live in the Chicago area and I run the 92 C and even on the coldest mornings it will start to give heat within a 3 minutes of driving. It takes a bit longer if you just let it idle.