Originally Posted by blutak
what did AUC say? I noticed my 330d this week had started bouncing on idle, (slightly misfiring).
I went to Williams BMW in Manchester today and explained that my temps didnt go above 80 regardless of driving style or duration and they just rung me back saying they've tested it and the thermostats are operating correctly for the current climate?
I thought the whole point of a thermostat was to maintain the temperature of the engine regardless of current climate? Any ideas?? They did however say i had a faulty glow plug control unit which will be replaced under warranty.
Does anyone know if 90 degrees C is definitely the operating temperature?
Don't these garages talk rubbish. A thermostat that is rated at 88C means that is the lowest temperature an engine will run, when there is a decent heat soak in the engine and on the run.
Garages often "test" (for lack of a better word) in a workshop, with no air cooling and they get high ECT. Doesn't mean a thing, on a complex cooling circuit, where there are secondary flows such as with the EGR thermostat.
Look at this topic.
I posted the following just yesterday.
The main thermostat is rated at an opening temperature of 88C, hence the 88 - 92C working range we see in typical use. The same thermostat, as used in the Rover BMW M47R 2.0d engine is rated at 88C +/- 5C tolerance. BMW don't seem to declare that data for the BMW models.
EGR thermostat has twin stage elements, first stage 70C opening temperature, with restricted flow, and full flow (second stage) at 90C, to follow the main thermostat opening temperature. Otherwise (as another post states) the faulty EGR thermostat flow by-passes the main thermostat control and chills the engine, and/or prevents efficient warm up and optimum ECT.
If an EGR thermostat opens pre main thermostat (88C), assuming the main thermostat is still in tolerance, the engine will not reach peak ECT in normal use. Although it may still exceed 90C during a regeneration, as there is typically much more heat in the engine.
A 330d will run 90C+ no issues at all, in sub zero temperatures at a steady cruise of about 60mph, once up to temperature. All it requires are thermostats which are working in range.
The only issue with running diesels in colder temperatures is the warm up time, and a little drop off in ECT if the engine loadings are so low there is no spare heat to assist the heat up. Such as on a long downhill overrun. But constant cruising will have plenty of heat to regulate above main thermostat opening temperature, hence typical 88 - 92C ECT on the run.