When I bought my 3-series in January, the sales man told me that he had just changed the thermostat and that he thought some air was still trapped in the heater matrix. The Result? when the engine is at idle the heater blows cold air into the cabin and when the revs are above idle we have warm air again. Especially annoying in winter!
I have recently had to change the coolant as the bleed valve cracked and leaked coolant. After aquiring a new bleed valve I set about re-filling the coolant system to exacting instructions from my Haynes Manual. The result you may ask? exactly the same as before!!!!!!!!!!!!!!!!!!!!!!!!
Why is this happening? It is truly annoying! People have said to me that it could be the result of a faulty water pump but I doubt this as my car has never over-heated since buying it.
Does anyone have any handy hints and tips about good ways to the bleed the coolant system correctly?
And does anyone know why the M42 engine doesn't have a bleed valve on the thermostat housing as all other four cylinder engines in the range do?