[1966-TR4]

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.

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.

I maybe worded it clumsily - the coolant is up to temp before the oil. My concern was that without knowing its operating range I couldn't be sure whether it was starting off stuck open, and thus taking longer to get up to temp. Lowering temp whilst going down hill could also be a symptom of that, however it never went below 88/89 in those circumstances and now that I know the range am comfortable that was because the 'stat was doing its job.

In various petrol cars when I've had an issue with a thermostat a downhill coast has knocked down the coolant temp by 25% and it is nowhere near as bad as that in this case.

[HighlandPete]

Originally Posted by 1966-TR4

Lowering temp whilst going down hill could also be a symptom of that, however it never went below 88/89 in those circumstances and now that I know the range am comfortable that was because the 'stat was doing its job.

Yes you are definitely OK, if it isn't dropping back.

We don't appear to be having the same thermostat issues with N47/57 engines as we did in the M47/57 versions.

The N47/57 has just the one thermostat, not the added EGR thermostat which confused the mode of failure. The mode of failure for the main thermostat is usually opening early, gradually dropping from ~88°C, rather than sticking open.

Was the case with my M57, gradually dropped back to running ~85°C. When it dropped below that figure, I was prepared to change it.

[Hooded]

Originally Posted by HighlandPete

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.

Checked the hidden menu coolant temp on my remapped 64 plate F30 330d for the first time during cold weather today (only previously checked during summer on this car).
The weather was around 2c so quite cold and the coolant temp registered as 1c before starting the engine. The journey to the garden centre was quite short just over 10 miles but the oil reached the correct running temp of 100c a Couple of miles before reaching the destination.

Coolant initially warmed up quicker than the oil reaching 70c by the time the oil lifted slightly off the bottom (50c) on the gauge. Note: The oil gauge is very accurate on my car more or less identically matching the oil temp on the hidden menu whenever checking this. As the temps got closer towards 90c the oil temp temp caught up with the coolant temp gradually though and surpassed it by the time it reached over 90c.

As the oil had reached optimum running temp of 100c maybe a couple of miles before reaching the destination I monitored what the coolant was then doing in the cold weather with the heater also on high (missus was cold) potentially drawing a little heat from the engine. With the oil at optimum temp the coolant averaged 90-92c dropping no lower then 89c on very light load going downhill. Once reaching the garden centre I let the car idle a couple of minutes and the coolant sat at 90c.

We left the garden centre after around 25 minutes and both the oil and coolant had dropped to just above 80c after starting up the car back up. The Coolant went back up to 90c quicker than the oil and again stayed around 90-92c most of the time on the 6 mile drive to the next destination. The lowest the coolant dropped to on the second journey was again 89c on light load and the highest it reached this time was 94c accelerating up an incline. On reaching the destination I again let the car idle a couple of minutes and this time the coolant sat at 91c.

As expected even in colder temps the coolant doesn’t fall back below 88/89c again once the engine is fully up to 100c oil temp with a thermostat that appears to be working correctly.

Note: last time I checked the hidden menu temp was during summer in warm weather and the coolant reached a max of just over 100c on load, but that’s also with the AC on high rather than the heater drawing heat away.

[HighlandPete]

Originally Posted by Hooded

The weather was around 2c so quite cold and the coolant temp registered as 1c before starting the engine. The journey to the garden centre was quite short just over 10 miles but the oil reached the correct running temp of 100c a Couple of miles before reaching the destination.

I suggest the N57 engine warms a lot faster than the older M57. No way would my 330d heat that fast at 2°C.

I've just looked at some trips in the 330d, at 1 - 3°C, (new thermostats). After 10 miles the ECT was still climbing, but only 82°C, dropping back to 78°C on the easy descent over 1/2 mile.

Another trip, after 13 miles at 6°C, the ECT was still climbing, but only 87°C.

There are several factors which come into play. Battery condition and whether the electric PTC auxiliary heater is running full capacity, assisting cabin warm up. The mpg during the warmup phase, engine loads over the mileage.

It's one thing I notice with the 535i, all spare heat is used to heat the cabin, no electric auxiliary heating element to help the HVAC system. That definitely slows the warmup phase.

Consider the engine load factor, in the 330d. The above example was reading 36.2 mpg at the 10 miles mark. That's a light fuel consumption, from a 2°C cold start.

Another example in the 330d was 'up the glen' at -4°C, climbing about 200 metres in 8.3 miles. ECT was just tipping from 87 - 88°C when I turned around. OBC was recording 21.5 mpg.

Return trip to home, immediately dropped back to 85/86°C. After the 8.3 miles to home was just 83°C. OBC showing 29.1mpg. Load and mpg reflecting not enough work to heat the engine, simply cooling down over distance.

[Hooded]

Originally Posted by HighlandPete

I suggest the N57 engine warms a lot faster than the older M57. No way would my 330d heat that fast at 2°C.

I've just looked at some trips in the 330d, at 1 - 3°C, (new thermostats). After 10 miles the ECT was still climbing, but only 82°C, dropping back to 78°C on the easy descent over 1/2 mile.

Another trip, after 13 miles at 6°C, the ECT was still climbing, but only 87°C.

There are several factors which come into play. Battery condition and whether the electric PTC auxiliary heater is running full capacity, assisting cabin warm up. The mpg during the warmup phase, engine loads over the mileage.

It's one thing I notice with the 535i, all spare heat is used to heat the cabin, no electric auxiliary heating element to help the HVAC system. That definitely slows the warmup phase.

Consider the engine load factor, in the 330d. The above example was reading 36.2 mpg at the 10 miles mark. That's a light fuel consumption, from a 2°C cold start.

Another example in the 330d was 'up the glen' at -4°C, climbing about 200 metres in 8.3 miles. ECT was just tipping from 87 - 88°C when I turned around. OBC was recording 21.5 mpg.

Return trip to home, immediately dropped back to 85/86°C. After the 8.3 miles to home was just 83°C. OBC showing 29.1mpg. Load and mpg reflecting not enough work to heat the engine, simply cooling down over distance.

Speaking of Battery the car is just over 5 years old and on its original battery, although I’ve had no low battery warnings at all yet. The auxiliary heater was definitely in play today, there was warm air coming through to the cabin in less than 2 miles!

What I find aids engine warm up is accelerating a little on the inclines whenever possible, but of course not revving it too high while the engine is not up to temp yet.

You do see coolant temp drop back when off load if the engine hasn’t had chance to get completely heat soaked fully and up to optimum temp Yet. While mine was still warming up it dropped back from 80c to 76c going downhill, but once the engine was at the optimum oil temp of 100c you didn’t get any coolant drop back below the initial thermostat opening temp of 88c again. Your example above in -4c going downhill on the way back home and dropping back to 83c from around 87c was down to the engine never quite getting heat soaked enough to it’s optimum running temperature before starting back down hill in the cold.

[HighlandPete]

Originally Posted by Hooded

You do see coolant temp drop back when off load if the engine hasn’t had chance to get completely heat soaked fully and up to optimum temp Yet. While mine was still warming up it dropped back from 80c to 76c going downhill, but once the engine was at the optimum oil temp of 100c you didn’t get any coolant drop back below the initial thermostat opening temp of 88c again. Your example above in -4c going downhill on the way back home and dropping back to 83c from around 87c was down to the engine never quite getting heat soaked enough to it’s optimum running temperature before starting back down hill in the cold.

Yes, I'll see the drop back during the warmup phase, if the load reduces. An observation in the 535i, it typically cross references the instant mpg reading 50+ mpg, over a reasonable distance. Fits with no waste heat to spare.

There are no issues once the ambient temperature is above ~7°. Then it is progressive heating and holds above the thermostat opening temperature.

Radiator shutters are definitely the answer.

[Hooded]

Originally Posted by HighlandPete

Yes, I'll see the drop back during the warmup phase, if the load reduces. An observation in the 535i, it typically cross references the instant mpg reading 50+ mpg, over a reasonable distance. Fits with no waste heat to spare.

There are no issues once the ambient temperature is above ~7°. Then it is progressive heating and holds above the thermostat opening temperature.

Radiator shutters are definitely the answer.

Indeed... and also good for preventing stones from hitting the AC condenser which is common on the F3x!

[xpro]

I've been monitoring my 335xd for a while now with a BimmerLink app and the optimum coolant temp seems to be around 80/85c. No higher then that ever.
Oil temps take a while to warm up and also stay around 80c when fully warmed up.
If you drive the car hard the oil will go to 90c for very short periods and then back to 80c..

Bear in mind that with all this cold weather the car will use more fuel, as it takes longer to get upto operating temps as cold start injection will continue to run untill car is at least over 60% on the coolant temp.
I can also notice decline in mpg but i defo put it down to the weather

[HighlandPete]

Originally Posted by xpro

I've been monitoring my 335xd for a while now with a BimmerLink app and the optimum coolant temp seems to be around 80/85c. No higher then that ever.
Oil temps take a while to warm up and also stay around 80c when fully warmed up.
If you drive the car hard the oil will go to 90c for very short periods and then back to 80c..

Bear in mind that with all this cold weather the car will use more fuel, as it takes longer to get upto operating temps as cold start injection will continue to run untill car is at least over 60% on the coolant temp.
I can also notice decline in mpg but i defo put it down to the weather

Remember the thermostat for the 335d is rated at 87°C opening temperature. (88 - 100°C working range, BMW data). You are therefore running with a thermostat issue.

Oil temperature is also much too low at 80°C.

[xpro]

Originally Posted by HighlandPete

Remember the thermostat for the 335d is rated at 87°C opening temperature. (88 - 100°C working range, BMW data). You are therefore running with a thermostat issue.

Oil temperature is also much too low at 80°C.

Hey, its been like that from the day I got it. No faults recored either and Ista confirms this is within the range.

When the regen is on the temps go up to 87c which proves the stat is working fine, which means it won't let the temperatures exceed that value.

I guess if the stat was faulty the temps would be even lower especially when cruising at high speed as the radiator is being cooled.

The 88c figure might have been for older cars, unless there was a change in the thermostats in the newer vehicles.
My mates M4 runs at 79c and that is the range for M motors.

Screenshot from dpf regen

[HighlandPete]

Originally Posted by xpro

Hey, its been like that from the day I got it. No faults recored either and Ista confirms this is within the range.

When the regen is on the temps go up to 87c which proves the stat is working fine, which means it won't let the temperatures exceed that value.

I guess if the stat was faulty the temps would be even lower especially when cruising at high speed as the radiator is being cooled.

The 88c figure might have been for older cars, unless there was a change in the thermostats in the newer vehicles.
My mates M4 runs at 79c and that is the range for M motors.

87°C for a regeneration is very low and the fact your motor increases to that figure, doesn't mean there isn't a problem with the thermostat. If it is opening at a lower than optimum figure (as failing stats often do), it may be pretty consistent, but not high enough.

There won't be fault codes on the 335d, as it uses a mechanical thermostat. M4 is different, that is running a map thermostat, ECT will be monitored including load, to run an appropriate temperature.

My N55 engine runs a map thermostat, the mechanical part is rated at 97°C, with a 'map' similar to the M4's. Typically runs at ~102°C, once stable.

[Hooded]

Originally Posted by xpro

Hey, its been like that from the day I got it. No faults recored either and Ista confirms this is within the range.

When the regen is on the temps go up to 87c which proves the stat is working fine, which means it won't let the temperatures exceed that value.

I guess if the stat was faulty the temps would be even lower especially when cruising at high speed as the radiator is being cooled.

The 88c figure might have been for older cars, unless there was a change in the thermostats in the newer vehicles.
My mates M4 runs at 79c and that is the range for M motors.

Screenshot from dpf regen

The N57 engine does not run below 88c once fully warmed up and heat soaked if the thermostats are working correctly.

How long are your journeys that you are monitoring the temps on? .. Have you tried monitoring the temps through the hidden menu rather than the phone app? I’m just wondering if it’s reporting the correct temp on the app or not.

[HighlandPete]

Originally Posted by Hooded

The N57 engine does not run below 88c once fully warmed up and heat soaked if the thermostats are working correctly.

How long are your journeys that you are monitoring the temps on? .. Have you tried monitoring the temps through the hidden menu rather than the phone app? I’m just wondering if it’s reporting the correct temp on the app or not.

Good point on the app. If it is the same phone app being used for both the 335d and M4, there could be an issue.

Both engines are definitely reading low. The M4 should be reading an ECT of over 100°C, in normal running. The thermostat (mechanical function) is rated to open at 105°C.

[Watsey]

Originally Posted by Hooded

The N57 engine does not run below 88c once fully warmed up and heat soaked if the thermostats are working correctly.

How long are your journeys that you are monitoring the temps on? .. Have you tried monitoring the temps through the hidden menu rather than the phone app? I’m just wondering if it’s reporting the correct temp on the app or not.

Some of the Apps gave a substantial number of sensor reading options. It's possible that the wrong sensor/output has been selected in the config.

[salimshk]

Originally Posted by HighlandPete

Good point on the app. If it is the same phone app being used for both the 335d and M4, there could be an issue.

Both engines are definitely reading low. The M4 should be reading an ECT of over 100°C, in normal running. The thermostat (mechanical function) is rated to open at 105°C.

Well what a fantastic, nail biting discussion between Highland Pete and Hooded. Lmao, no sarcasm here, I've been in the same boat for the last few years.

Highland Pete I have seen your discussions on other forums over the years and you usually have experienced and resolved those niggling issues that other people normally give up on. In this particular case though, I believe you might be wrong, as much as it would be easier for me to accept that you are correct.

I replace the thermostat(s) on every BMW I buy as a matter of course. On all of my previous BM's such as the E36's, E46's, E39's etc, it was simple, replace the stat, ensure coolant temp is between 88 and 92 and that's it, job done, mpg is noticeably improved. On a good stat, the coolant temperature never ever dropped below 88c on these generation of BMW's no matter what the ambient temperature was.

Then I bought my first E92 (330D) around 6 years back. The temperature band was a bit wider but even then after replacing the stat, the temperature did not drop below 88c for the first few years. MPG on a run (70 with cruise control) would be low 40's regardless of time of year. When I then had to replace my water pump a few years later I noticed the temperature would hit 88c and then on light load drop a few degrees below. I replaced both stat's with genuine bmw ones again. Problem persisted. MPG in exact same conditions was 37mpg. I eventually gave up after realising I was spending more on parts than I would on fuel.

I've now bought an E93 330D. Same thing again, stats were shot so replaced with genuine BMW ones. Temperature now gets up to 88c within 5-10 mins but will easily drop below 88c on light load. MPG in the same conditions in 37mpg.
This has been the case since I purchased it last year but after reading this discussion I thought I'd give your theory a try. Ambient temperature was 15c yet on light load the temp drops below 88c. It is not overcooling because of ambient conditions in my opinion.

The only thing I can think of, which a manager at BMW mentioned to me was the gearbox thermostat. I did not even know this existed but at that point I could not be bothered to chase the issue any longer. Any chance your cars that exhibited these symptoms were automatic?

[HighlandPete]

Originally Posted by salimshk

The only thing I can think of, which a manager at BMW mentioned to me was the gearbox thermostat. I did not even know this existed but at that point I could not be bothered to chase the issue any longer. Any chance your cars that exhibited these symptoms were automatic?

Well.. a thread resurrection.

Ah, the AT thermostat... we did beat that one to death in other topics. I know it was included in many of the E9x/E6x discussions where engine thermostats were changed and no changes to ECT. Often the temperature would not climb to much more than 75C, a bit like failed EGR thermostats. Without reading all the thread again, not sure we covered all bases here.

If I remember correctly, I think on the E60 there is a hose that can be clamped to eliminate the AT thermostat. Can't recall without back reading, if there is a similar trouble shoot path on the E9x models.

[Eddamoo]

I personally think its just crap engineering. You wonder how its still possible in this day, but BMW managed to make real clangers like the N20 engine so i wouldn't put it past them.

I've felt my main Rad on warmup - the hot water slowly bleads the full way across it while the engine idles away with the thermostat closed, this would be worsened by driving with a headwind.

The Thermostat is downstream of the Gearbox heat exchanger AND the Rad so there's a huge amount of thermal conduction going on away from the engine block. Most manufacturers put the Thermostat directly downstream of the block and certainly upstream of the Rad.

I also wonder whether ~10% coolant temp could contribute a whopping 20%+ to fuel economy. I certainly doubt that's the cause. The engine should be in closed-loop emissions control/fuel delivery well before that.

[Tony B]

I have been reading through this thread with much interest as I have similar issues with my E91 330D (MY2010).

Slow warm-up, hardly ever getting into the 80s C, and a good 15% thirstier than it was a year or 2 ago (now 64 k miles, full BMW service history and extended warranty).

Catalyst temperature only occasionally getting above 350C (more normally in the low 200s).

Dealer detected errors on 5 of 6 glow plugs, and GP control unit, replaced these, and after some pressure from me also replaced the main coolant thermostat.

The improvement was significant, but very limited timewise.

First drive home the fuel consumption got back to 42mpg (UK gallons), even in traffic (which is how it used to be), but has since rapidly declined to about 32mpg.

Monitoring various parameters with the BMW Drive Analyser app, shows strange (to me) Lambda numbers, which constantly return to 1.40 once warm, with little variation as the accelerator is modulated.

The only time the Lambda gets throttle sensitive is when the engine seems to get into a regen process (holding lower gears for much longer, cat temperature then climbs up to high 500s for a few moments). At this time the Lambda changes just as I would expect it to.

EGR valve has not been replaced.

I am tempted to change this myself, but do not want to invalidate the warranty.

Please see attached link, where I go into more details.
https://www.pistonheads.com/gassing/...f=72&t=2068053