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Yeah, I'm aware of that. However, when sweeping up from below normal temp to normal temp, it will first go into the normal temp position at the same temperature (when it crosses the minimum temp for the normal temp range).
Which is weird, because I freaked out when I first learned it's fake, and I'm still not happy about it.
Guess they made it doctored because coolant temperatures changed constantly and in the past people might had complained something wrong with their car.
Guess they made it doctored because coolant temperatures changed constantly and in the past people might had complained something wrong with their car.
Yeah, I kinda get it... Kinda.
They should have made the gauge behavior codable though.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
It's not just Mercedes that does this thing with the temperature gauge. Virtually every manufacturer does it. Certainly VW/Audi does it with their cars.
Vagaries of the modern temperature gauge aside, mine indicates what I interpret as the normal operating temperature to be one tick above 80°C (the spacing of the ticks suggests this is 87.5°C, but that's a little silly to take literally). This morning, I paid extra close attention to the gauge (as close as can be paid while driving a 5yo to school on icy canyon roads). I started the car and just drove, no warm up time. The drive is 16 minutes, and 8.4mi each way. Going in, it's essentially 100% downhill or flat, with the first ~2/3 being a pretty steep grade. Drive back is the opposite. There's a ~5 minute engine off period in the middle. Temps were low-mid 20°s F up here, and about 10°F warmer in the flats. The gauge didn't read "ready for business" until I was a little over halfway back home.
Yesterday, I didn't pay as close attention, but it was a longer first drive. 22.5 miles over 39 minutes. 1k' greater descent. Probably 10°F colder. I was going down the highway at 60mph, and watching the temp gauge drop to just one tick above the 40°C minimum... Basically didn't make it to temp until I was at about the same point as the previously described scenario halfway back home.
If the engine is taking care of itself, that's fine and good. I don't want to put unnecessary wear on it. I'd like it to last a while. It's pretty annoying to have a great big V8 under the hood that I just can't use because it never gets warm enough to uncork. Also annoying is the poor fuel economy I get while it's in whatever warmup mode. More than annoying, especially with small children, is that I don't have heat. Heated seat is great. Lack of a heated steering wheel sucks (sport wheel). But the kids just get to freeze.
It sounds like this may not be entirely unexpected behavior. I have to take it to the dealer for some work, but I want to wait until I can get the (mid engine, rear wheel drive, street slicks) sports car out of the barn for spring so that my wife and I can still get around without having to dance around each other.
My feeling right now is that the answer is likely to find some sort of remote start setup so that I can give it a few minutes before we get in to have a chance to get some heat in it, but even that is going to require research and install time that I doubt I'll be able to come up with before spring...
I don't know if it's normal or not, but your experience matches mine. Remote start might help a bit, but only if you're willing to cold idle your car for way longer than I would be.
The M278 generates a ton of heat, but it may come mostly from the turbos, and at idle or driving with a mostly closed throttle they aren't doing much.
If you have an outlet nearby, the best approach is to use a block heater like they do in Northern Europe. I installed one on my airplane to limit how much I trashed the engine on cold starts in the winter and it worked wonders. This way you just avoid cold starts altogether.
Looks like Mercedes might not have a block heater option for the M278, but there are non-engine specific options which are probably easier to install than a remote start system.
A Swedish company makes one for the M276, maybe it would also work for the M278. I would be interested if I had a place to plug in near where I park...
I understand but I monitor the temperature, I have it unplugged for almost a year and the temperatures raise quicker in the summer and winter again, this is different engine to yours, M276, so YMMV for sure.
To clarify, I am saying that yes, the oil solenoid mod can make the engine oil heat up quicker, but regardless, in winter it is a longer process, for me me, much longer in winter, once temps reach the thirties and of course if it’s been in the single digits. The greater point was is the oil mod only does so much in cold weather onto counteract the coolers being much colder. Ime.
Vagaries of the modern temperature gauge aside, mine indicates what I interpret as the normal operating temperature to be one tick above 80°C (the spacing of the ticks suggests this is 87.5°C, but that's a little silly to take literally). This morning, I paid extra close attention to the gauge (as close as can be paid while driving a 5yo to school on icy canyon roads). I started the car and just drove, no warm up time. The drive is 16 minutes, and 8.4mi each way. Going in, it's essentially 100% downhill or flat, with the first ~2/3 being a pretty steep grade. Drive back is the opposite. There's a ~5 minute engine off period in the middle. Temps were low-mid 20°s F up here, and about 10°F warmer in the flats. The gauge didn't read "ready for business" until I was a little over halfway back home.
Yesterday, I didn't pay as close attention, but it was a longer first drive. 22.5 miles over 39 minutes. 1k' greater descent. Probably 10°F colder. I was going down the highway at 60mph, and watching the temp gauge drop to just one tick above the 40°C minimum... Basically didn't make it to temp until I was at about the same point as the previously described scenario halfway back home.
If the engine is taking care of itself, that's fine and good. I don't want to put unnecessary wear on it. I'd like it to last a while. It's pretty annoying to have a great big V8 under the hood that I just can't use because it never gets warm enough to uncork. Also annoying is the poor fuel economy I get while it's in whatever warmup mode. More than annoying, especially with small children, is that I don't have heat. Heated seat is great. Lack of a heated steering wheel sucks (sport wheel). But the kids just get to freeze.
It sounds like this may not be entirely unexpected behavior. I have to take it to the dealer for some work, but I want to wait until I can get the (mid engine, rear wheel drive, street slicks) sports car out of the barn for spring so that my wife and I can still get around without having to dance around each other.
My feeling right now is that the answer is likely to find some sort of remote start setup so that I can give it a few minutes before we get in to have a chance to get some heat in it, but even that is going to require research and install time that I doubt I'll be able to come up with before spring...
Some of which heats up slower when driving on the highway such as the transmission than say in stop and go traffic as on the highway there is less shifting activity.
Yes I am not sure it is a good idea to remote start and let it idle stationary as there might be more wear to the engine with the cold oil, the other parts of the drivetrain also doesn't get to heat up as well as if you were to drive it.
Last edited by W205C43PFL; Jan 24, 2025 at 07:22 PM.
To clarify, I am saying that yes, the oil solenoid mod can make the engine oil heat up quicker, but regardless, in winter it is a longer process, for me me, much longer in winter, once temps reach the thirties and of course if it’s been in the single digits. The greater point was is the oil mod only does so much in cold weather onto counteract the coolers being much colder. Ime.
I'm pretty sure the ECU cuts fuel when coasting. Pretty standard mapping post... just about the advent of ECUs capable of having maps (the only exception I can think of is Mazda rotaries, because they need to inject and burn oil in every revolution). Cold and a lot of fluid is a big part of the problem, but coasting for long periods off throttle means the engine is actively cooling itself. Wear from sitting and idling certainly isn't great, but it's no worse than living in an urban environment, and no one says boo about that. Wear from extended high speed everything while cold extends that tremendously. Monday, I'll give it a test run with a pre-start. See if it makes things any better.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by W205C43PFL
Yes I am not sure it is a good idea to remote start and let it idle stationary as there might be more wear to the engine with the cold oil, the other parts of the drivetrain also doesn't get to heat up as well as if you were to drive it.
See, if you got the remote that you could have got, if you got but did not get....well, then you could have remotely started as it would have been able to remotely start, had you only got the remote start feature.
Way, WAY back in 1999 when I was first driving (or so I thought)...we had remote start in my mothers Jaguar XJS...."hey, take the key, go start the car, I need to go to the liquor store and buy cigarettes....."
That car never started in the cold, often did not start in the warm either....
See, if you got the remote that you could have got, if you got but did not get....well, then you could have remotely started as it would have been able to remotely start, had you only got the remote start feature.
Way, WAY back in 1999 when I was first driving (or so I thought)...we had remote start in my mothers Jaguar XJS...."hey, take the key, go start the car, I need to go to the liquor store and buy cigarettes....."
That car never started in the cold, often did not start in the warm either....
Ah yes yes, that is a different type of remote start : )
Well, there is keyless start standard on many vehicles then keyless go is an option... I still don't think it is related to this "startable" feature though.
The plot thickens. I was down in the flats running errands yesterday. Went way too long without ever getting up to temp, as usual. Then the check engine light came on. I'll pull the code today, but I have money saying it's thermostat related.
The plot thickens. I was down in the flats running errands yesterday. Went way too long without ever getting up to temp, as usual. Then the check engine light came on. I'll pull the code today, but I have money saying it's thermostat related.
0856 - The coolant temperature is below the coolant thermostat specified temperature. The "Googlit" button on the scanner says failed thermostat. Didn't throw the code until I was going ~65 mph, and seems to have thrown it twice around that speed. I don't typically go that fast up here recently for obvious reasons (imagine winding canyon roads in winter), so that checks out too. Seems my intuition was right that it wasn't behaving like it should. Now I need to find a shop that likes my warranty that isn't the shop I took it to most recently that screwed up more than they fixed (which they owned up to, and made right), and also failed to actually fix more than half the ailments I brought it to them for.... Any recommendations in the (SW) Denver area?
0856 - The coolant temperature is below the coolant thermostat specified temperature. The "Googlit" button on the scanner says failed thermostat. Didn't throw the code until I was going ~65 mph, and seems to have thrown it twice around that speed. I don't typically go that fast up here recently for obvious reasons (imagine winding canyon roads in winter), so that checks out too. Seems my intuition was right that it wasn't behaving like it should. Now I need to find a shop that likes my warranty that isn't the shop I took it to most recently that screwed up more than they fixed (which they owned up to, and made right), and also failed to actually fix more than half the ailments I brought it to them for.... Any recommendations in the (SW) Denver area?
Your coolant thermostat is now stiff and lazy hard to react/actuate.
When you hop-on the highway engine gets too cold... ***
Still, this is better than warping the heads during summer heatsoak.
I am not going to comment on warranty work... lot of collateral parts involved including 5¢ O-rings that will slow-leak if not replaced (I have this myself).
Be smart about this repair... give the shop a bone to wanna help you: "serpentine service kit (tensioner/belt/idlers) - Shops don't work for cut-throat warranty claim adjusters... they work for customers.
***FYI: even a new Tstat Gets Lower temp on highway but not so low a fault is logged. I guess MB is using that challenge to test the Tstat response.
Tstat can not tolerate being marginal. Extreme heat is caused by engine timings, not Tstat alone.
Last edited by CaliBenzDriver; Jan 27, 2025 at 12:56 AM.
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