Can over cooling be caused by air?
I know most mentions of lack of correct bleeding revolve around over-heating.... I have over cooling - my temp gauge never reads 12, always the tick before that, so I read through the advice here and assumed a bad stat (I've already replaced it but with a cheap one) so I just bought a new stat from the dealer and installed it and still same problem. One thing though, my thermostat cover's bleed screw is jammed in tight and the nut is worn away.... I tried with WD40 and pliers and various things and I just could not get it loose, so I can't bleed from the stat housing - is an air bubble there likely to be causing my problem? I'm going to call the dealer today and see if they've got a new cover in stock (I ordered in and got a new bleed screw but I cannot get the old one out at all).... do you think that will solve it or am I barking up the wrong tree completely?
Thanks
Doogie
I believe the needle should always be at 12 o'clock
to get the most from the engine. The engine control management system is designed to work with a thermostat set to a specific temperature whether it's 88 C or 82 C (or 81 C I think). A temperature that is constantly lower than this may not allow the computer to control the engine properly for operation at peak performance. Maybe others here on the board may have additional insight.
Here's an excerpt on a similar topic
http://www.northstarbmw.org/index.aspx?ns=TechArticles
"Thermostats maintain the correct temperature for both the passengers and the motor. If your thermostat is allowing your engine to run cooler than recommended the engine computer may never allow the fuel injection to work properly, causing poor fuel mileage, high emissions, poor performance and possibly fuel dilution in the motor oil. Typically, you would see this as a drop in engine temperature in cold weather, especially in highway driving. In the last few years BMW is using a computer controlled thermostat to allow for tighter control of engine temperature. This is done by building a "normal" thermostat that runs at a very high temperature. Incorporated in the design is a very small electric heating element that is controlled by the engine computer. By using the coolant temperature sensor as a feedback signal the engine computer can regulate the engine temperature by supplying current to this heating element as needed to cool the motor. Unfortunately BMW missed the mark in an early design of these thermostats on the six cylinder motors. An unacceptable level of failed thermostats has led to many cars being recalled to have the thermostat replaced with the newest design. Owners of affected vehicles will receive a notice in the mail from BMW."