[1966-TR4]

hi, does anyone know what the normal coolant operating temp is for a 330d?

For the last couple of weeks I have suspected a stuck or sticking thermostat - MPG is down about 10% and oil temp on my regular 60 mile commute is taking longer than normal to get up to 100 on the gauge. Weather has not been especially cold.

Last night I drove home with the coolant temp up on the display via the Hidden Menu. When oil eventually got up to temp, coolant was hovering around high 80s. Once on the motorway, it ranged between 89 and 99, generally mid 90s. Going downhill with no load on the engine I could bring them temp down from the upper to the lower end of that range.

So I guess the question is - does it sound like it's running too cool?

Additionally, does the oil cooler have its own thermostat?

[Watsey]

I asked my BMW dealer what the coolant operating temp range is, and they didn't know. FFS.

I find that my mpg plummets in the winter, especially on short journeys when the ambient temp is (say) <10C. I commonly see mid-20s mpg by the end of a tank of fuel. That's around a 10mpg drop.

The 30d (and presumably the 35d) has an auxiliary electric heater for the cabin because the engines take longer to warm up which means longer for warm/hot coolant available for the heater matrix. This places additional load on the alternator and therefore the engine.

Using the hidden menu I have typically seen 90-108C coolant temps but I remember that it was summer temps when I was checking.

I'm not sure about an oil thermostat. I assume there is one, but I haven't checked in realoem.

[HighlandPete]

Coolant thermostat starts opening at approximately 88°C. Fully open at 100°C.

So you are right in the working range.

[Hooded]

Last time I checked the hidden menu mine reached just over 100c once fully warmed up, but like watsey.. this was also during summer.

[HighlandPete]

The other question... Yes, there is an oil cooler thermostat and a transmission oil thermostat, they are internal, all part of the oil filter module.

[HighlandPete]

Originally Posted by Hooded

Last time I checked the hidden menu mine reached just over 100c once fully warmed up, but like watsey.. this was also during summer.

100°C or above is going to be the top end, (for a diesel) as the thermostat is fully open and getting maximum cooling from the system.

Winter time, many users won't get much above 90°C, unless during a DPF regeneration. Those running maps or mods' may be a bit higher.

[1966-TR4]

Thanks everyone, sounds like I may be chasing ghosts.

[HighlandPete]

Originally Posted by 1966-TR4

Thanks everyone, sounds like I may be chasing ghosts.

If you have been having temperatures anything like me, then warm ups will be slower. Even my petrol is slow to warm. No different than any other winter, but more noticeable once we drop below about 7°C. Hidden Menu is showing temperatures/over distance virtually the same as my first winter.

BTW, the oil control thermostats are replaceable, as a 'layer', within the oil filter module. Not cheap, and not sure how you'd easily test them for efficiency and correct working temperature.

[Hooded]

Originally Posted by HighlandPete

100°C or above is going to be the top end, (for a diesel) as the thermostat is fully open and getting maximum cooling from the system.

Winter time, many users won't get much above 90°C, unless during a DPF regeneration. Those running maps or mods' may be a bit higher.

I’ll check mine soon on a cold day out of curiosity. Yes my car is remapped too.

To the OP.. as long as it’s not dropping below 88/89c again once completely heat soaked after a long drive I think your thermostat is fine!

[HighlandPete]

Originally Posted by Hooded

To the OP.. as long as it’s not dropping below 88/89c again once completely heat soaked after a long drive I think your thermostat is fine!

Holding the temperature, once a thermostat cracks open, is what we expect and is pretty much the case. But there is a caveat, diesel on a light load can still be overcooled, at lower ambient temperatures. Thermostat will be shut, and still the ECT drops.

I've monitored this in several diesel vehicles, where ECT and oil temperature will drop back on an easy run, below optimum running temperatures, due to chilling from airflows around the engines.

I totally understand why active shutter grilles are being introduced, to help keep up efficiency.

[Hooded]

Both E90 320d’s I owned in the past never dropped back below 88c once fully warmed up unless the thermostats were going a bit lazy. Once replaced they maintained 88c minimum in all weather.

[HighlandPete]

Originally Posted by Hooded

Both E90 320d’s I owned in the past never dropped back below 88c once fully warmed up unless the thermostats were going a bit lazy. Once replaced they maintained 88c minimum in all weather.

Not up here in 'winter conditions'. Temperatures around freezing.

My M57 330d (with new thermostats), I'd still see it dropping back, after the thermostat had clearly opened (~88°C) and been running say 8 miles ~90°C. I'd drop down into the village, off throttle, and I'd often see the ECT drop back to ~85°C. Drive through the village at 30mph and it still wouldn't regain the optimum ECT, until out of the village again.

Even the N55 in the 535i will do the same, drop back a few degrees below the running temperature. It is also overcooled at light loads in winter temperatures.

[Hooded]

Originally Posted by HighlandPete

Not up here in 'winter conditions'. Temperatures around freezing.

My M57 330d (with new thermostats), I'd still see it dropping back, after the thermostat had clearly opened (~88°C) and been running say 8 miles ~90°C. I'd drop down into the village, off throttle, and I'd often see the ECT drop back to ~85°C. Drive through the village at 30mph and it still wouldn't regain the optimum ECT, until out of the village again.

Even the N55 in the 535i will do the same, drop back a few degrees below the running temperature. It is also overcooled at light loads in winter temperatures.

Pete, in my opinion the thermostats a bit lazy if it drops down as far as 85c once the engine is ‘fully heat soaked’ even in sub zero temps. From experience of changing lazy thermostats in 2 E90 diesels where it was common for both engine and EGR stats to stick open a little after only a few years use, I can honestly say both my cars never dropped below 88c once fully warmed up properly with new genuine thermostats fitted, and yes we do sometimes get sub zero temps during winter here in the midlands With the new stats fitted they used to sit around smack on 90c with occasionally going a little higher under really heavy load or occasionally dropping back to 88/89c under very light load in cold weather.
I regularly used to check the coolant temps on these E90 diesel cars as the stats failed so often/easily.
Personally I don’t change the thermostats until they start dropping back as low as the low 80s though, that’s when you tend to notice a slight hit in mpg.

[Eddamoo]

Originally Posted by 1966-TR4

When oil eventually got up to temp, coolant was hovering around high 80s. Once on the motorway, it ranged between 89 and 99, generally mid 90s.

When troubleshooting a faulty thermostat, its all about how long the coolant system takes to warm up, not the final running temperature (as the fans will manage this once fully hot). In all my previous cars (petrols and diesels), the Oil temp took roughly double the time to reach 85C than the coolant.

If i'm reading your above comment correctly, your coolant is coming up to operating temp AFTER the oil - that doesn't sound right to me. I am unsure if this is an attribute of the coolant/oil heat exchanger but will try to monitor my 430d on the way home tonight to check and will report back FYI.

All my cars have cooled when going down hills. I live in Sheffield right next to the Peak District - the car often hits 90-100 when driving up to the peaks and drops right back to 60-70C again in the bottom of a valley.

[HighlandPete]

Originally Posted by Hooded

Pete, in my opinion the thermostats a bit lazy if it drops down as far as 85c once the engine is ‘fully heat soaked’ even in sub zero temps. From experience of changing lazy thermostats in 2 E90 diesels where it was common for both engine and EGR stats to stick open a little after only a few years use, I can honestly say both my cars never dropped below 88c once fully warmed up properly with new genuine thermostats fitted, and yes we do sometimes get sub zero temps during winter here in the midlands With the new stats fitted they used to sit around smack on 90c with occasionally going a little higher under really heavy load or occasionally dropping back to 88/89c under very light load in cold weather.
I regularly used to check the coolant temps on these E90 diesel cars as the stats failed so often/easily.
Personally I don’t change the thermostats until they start dropping back as low as the low 80s though, that’s when you tend to notice a slight hit in mpg.

Seen it in too many diesels, to know it is not a thermostat issue. Simply over cooled.

Even in the warm up phase, when thermostats are firmly closed, I can see a drop back in ECT and oil temperature, simply descending down to sea level on a light throttle, over a mile or so. In the 535i it will do this if the ambient temperature is below ~6°C.

[HighlandPete]

Originally Posted by Eddamoo

When troubleshooting a faulty thermostat, its all about how long the coolant system takes to warm up, not the final running temperature (as the fans will manage this once fully hot). In all my previous cars (petrols and diesels), the Oil temp took roughly double the time to reach 85C than the coolant.

I think we will find ECT and oil temperature will vary in heat up times, depending on the engine series. The old M-series diesel were very slow to heat the oil, compared to ECT. I agree that many engines, oil will take twice the time to heat to optimum, in colder temperatures.

Latest designs give more attention to heating the oil faster, (makes a lot of difference to reducing parasitic losses), but can have the downside of slowing the ECT rise.

Take my N55 petrol, that has oil jets aimed at the underside of the pistons, both for cooling and the benefit of faster oil heat up. I find oil temperature, during the warmup phase, trails by about 4°C below the ECT, but levels out as the ECT comes into optimum range. By the time the ECT is 99°C, the oil is also reading 99°C. The down side... warmup is so slow in colder temperatures.

We run VW T5/6 diesel vehicles in the family. They have a digital oil temp' in the OBC sequence. Can see the oil temperature trailing so far behind ECT, at freezing temperatures. Any light load and it will drop back significantly, even after ECT is up to full operating temperature. Freezing air flows simply chill the engine bay and there is not enough waste energy to keep it hot.

[Eddamoo]

Originally Posted by HighlandPete

I think we will find ECT and oil temperature will vary in heat up times, depending on the engine series. The old M-series diesel were very slow to heat the oil, compared to ECT. I agree that many engines, oil will take twice the time to heat to optimum, in colder temperatures.

Latest designs give more attention to heating the oil faster, (makes a lot of difference to reducing parasitic losses), but can have the downside of slowing the ECT rise.

Take my N55 petrol, that has oil jets aimed at the underside of the pistons, both for cooling and the benefit of faster oil heat up. I find oil temperature, during the warmup phase, trails by about 4°C below the ECT, but levels out as the ECT comes into optimum range. By the time the ECT is 99°C, the oil is also reading 99°C. The down side... warmup is so slow in colder temperatures.

We run VW T5/6 diesel vehicles in the family. They have a digital oil temp' in the OBC sequence. Can see the oil temperature trailing so far behind ECT, at freezing temperatures. Any light load and it will drop back significantly, even after ECT is up to full operating temperature. Freezing air flows simply chill the engine bay and there is not enough waste energy to keep it hot.

Great post, very informative. I wish the F3x had a CT gauge. I do suspect the M57 heat oil much faster than my previous cars. Ill try to compare.

[Hooded]

Originally Posted by HighlandPete

Seen it in too many diesels, to know it is not a thermostat issue. Simply over cooled.

Even in the warm up phase, when thermostats are firmly closed, I can see a drop back in ECT and oil temperature, simply descending down to sea level on a light throttle, over a mile or so. In the 535i it will do this if the ambient temperature is below ~6°C.

Pete, Perhaps the thermostat is getting slightly lazy in your 535i if it’s dropping back off again a little once fully heat soaked?
I can only go on my own experience with 2 E90 diesel cars regarding coolant running temp though, and that is that the only time a fully heated up engine dropped back below around 88c on these M47 engined cars was when the thermostats were starting to gradually get lazy. It starts off slightly how you describe, dropping back to 86/87c on low load, then a year later it’ll be 84/85c etc. Seen this happen on E90’s. once the new genuine thermostat is in it stays at 88c+ All the time once fully warmed up for a couple of years at least usually. Once you start seeing drop back to 86/87c it’s the start of a gradual progressive failing of the thermostats in those cars.
I’m hoping they used more reliable ones in the F30 at least.

[SantaEugence]

My 330d, once warm, is dead on 100c never above never below.

[HighlandPete]

Originally Posted by SantaEugence

My 330d, once warm, is dead on 100c never above never below.

The gauge will be reading oil temperature, 100C is about it for a diesel.

[HighlandPete]

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?

I'll dig out some data I've recorded over the years and come back to this one. Including some experiments from running today. @ 4°C.

[HighlandPete]

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?

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.