Quote:
Originally Posted by Hooded
Pete, Perhaps the thermostat is getting slightly lazy in your 535i if it’s dropping back off again a little once fully heat soaked?
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After my own experience with the E91 330d and replacing the EGR thermostat and then the main thermostat due to it getting lazy, I realised the cooling systems and airflows are 'overkill' for typical Highland winters.
When I got the petrol 535i, I was disappointed that it didn't have the radiator shutter system that some F10/F11 models were fitted with. So started reading the temperatures, the first winter with the car, back in 2012. Warm-ups are so slow in winter, not much different from the diesel to be honest. Thought it would be better than it is, being a petrol engine, particularly after having the E39 V8 lump, which warmed up very fast considering its mass.
Looking at the records I've kept, there is very little change in my ownership. I'm getting the same temperatures, at the same ambient temperatures.
The comments on the ECT dropping off, under light loads, doesn't just apply to when the engine is up to temperature, also applies lower down the temperature in the warmup phase, when the thermostat is still closed. Was the same with the 330d.
Today I ran the temperature menu, started at 4°C and by the next village, after 3 miles at 55 - 60mph, ECT was 56°C. Running through the village the temperature dropped back to 54°C. Wasn't until accelerating out of the village did it start rising again.
After 10 miles, (yes 10 miles) the ECT was only 85°C. As I had caught up with a truck, (~45mph), the oil temperature also levelled out at 85°C. Next 1/2 mile or so was a light load, ECT dropped back to 82°C. Same as I've always seen at the lower ambient temperatures.
It took another 2 miles, at 30mph, to get both oil and ECT to 99°C, when I stopped for 5 minutes. Next bit of the trip was 4-miles at 30 & 40 mph, ECT never went above 99°C, oil peaked at 100°C for a few seconds and dropped back to 99°C.
Return trip, back through the glen (ambient at 4.5°C), I saw my normal winter running figures, 102°C ECT and 105°C for the oil.
I drop into the village off throttle, ECT drops back to 97°C, oil back to 101°C. Again, typical of what I've seen over the past 7-years.
Watching the temperature in warmer temperatures and at constant speeds, I detect the ECT thermostat cracks open around 99°C, you get the delay or dip before climbing to ~102°C.
What I've noted and it's pretty consistent, I'd get these drop offs in the diesel below 7°C ambient. The petrol it's about 6°C.
Once above those thresholds, there isn't the drop off. To me, it teaches over cooling, not enough waste heat to keep to temperature. Perhaps I should try a piece of cardboard in front of the radiator, like folks did in the old days.
My next BMW must have active grilles. Will put an end to too much cooling and slow warmup times.
