Originally Posted by Mr Singh
Blimey, you would have thought BMW would make it little easier lol.
So theres a main thermostat and an EGR one too.. I'm guessing that checking the engine temps won't really tell you which item is duff?
We are not supposed to be needing the ECT, or the other hidden data.
No, the temperature won't tell which is at fault, but will gives some pretty good clues. Very low ECT averages are typically the EGR thermostat, can be open from room temperature, so usually a long warm up time/mileage as well.
But often, even after the EGR 'stat change, the temperature is still lower than it ought to be. the main 'stats seem to lose their optimum range and run low, slowly degrading over time, rather than a complete failure.