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What is the normal operating engine temp range of the S550?

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Old Apr 16, 2022 | 03:52 PM
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From: Tewksbury, MA
2008 S550
What is the normal operating engine temp range of the S550?
Picked up my new to me 2008 S550 4MATIC today and drove home about 60 miles with the outside temp in the low 70's. The temp gauge assuming the hash marks are linear was around 90 degrees C. Is that about right?

Also on the center computer screen the AC always says OFF even when I use the knob to check off the box on the command panel. Normal?
Last edited by RichDMB; Apr 16, 2022 at 07:02 PM.
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Old Apr 16, 2022 | 03:59 PM
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Yes, that is normal. The M273 engine has an electronic coolant thermostat and you will notice how quickly it warms up. All in the name of efficiency and emissions control.

https://en.wikipedia.org/wiki/Mercedes-Benz_M273_engine
Last edited by lkchris; Apr 16, 2022 at 04:02 PM.
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Old Apr 16, 2022 | 06:59 PM
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This place is a joke.
90-100c is normal. OFF is always there. The checkbox turns the AC compressor on/off.
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Old Apr 16, 2022 | 07:04 PM
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Thanks guys! High temps scare me. On the BMWs I've had the temp was always dead in the middle; I guess Mercedes is a different animal.
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Old Apr 16, 2022 | 10:08 PM
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Aluminum blocks run higher water jacket temps than iron. Totally normal. You gonna be doing your own work on this thing?
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Old Apr 16, 2022 | 10:45 PM
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I will do what I can, I just don't like going under the car. Plan on changing the spark plugs and air filter shortly, brakes seem easy based on youtube videos I've seen. I can turn a wrench and do basic stuff. Kind of looking forward to it a bit!
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Old Apr 17, 2022 | 12:57 AM
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Originally Posted by RichDMB
Thanks guys! High temps scare me. On the BMWs I've had the temp was always dead in the middle; I guess Mercedes is a different animal.
BMWs are scary when it comes to engine temperature. A cylinder head on an inline 6 is a quite long casting. I once read something to the effect that if there was a sudden loss of coolant at highway speed, it was 6 seconds before the head warped from the excess temperature. Perhaps urban legend, but plausible.

Heads covering just 3 or 4 cylinders should be more resistant.

Of course now Mercedes is back to offering inline 6s … easier to turbocharge.
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Old Apr 17, 2022 | 01:09 AM
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Originally Posted by RichDMB
I will do what I can, I just don't like going under the car. Plan on changing the spark plugs and air filter shortly, brakes seem easy based on youtube videos I've seen. I can turn a wrench and do basic stuff. Kind of looking forward to it a bit!
With the electrically operated parking brake, changing rear rotors is “interesting.” The Mercedes shop computer can deactivate them … the one time I’ve done it I did it with motor running and transmission in neutral (N). There are likely other solutions.

As regards spark plugs … this is a sore point for me. Bosch USA—which is a marketing organization—seems to think Americans demand resistor plugs, which is NOT what Mercedes specifies. Like older BMW motorcycles, it seems the only source for made in Germany non resistor Bosch plugs in the USA is the dealer.
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Old Apr 17, 2022 | 01:44 AM
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Originally Posted by lkchris
With the electrically operated parking brake, changing rear rotors is “interesting.”
Rears are just as boring to replace as any other car. No special procedures or funky quirks. What is so interesting about them?
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Old Apr 17, 2022 | 07:52 AM
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I'm curious about the rear rotor issue, too, as I'm about to replace mine. My understanding from watching videos is that you just have to not engage the parking brake...what am I missing?
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Old Apr 17, 2022 | 01:59 PM
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Originally Posted by nath_h
I'm curious about the rear rotor issue, too, as I'm about to replace mine. My understanding from watching videos is that you just have to not engage the parking brake...what am I missing?
Nothing. That's it.
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Old Apr 19, 2022 | 09:39 PM
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Originally Posted by Senecat
Nothing. That's it.
sorry, but rotors aren’t coming off with parking brake activated. Deactivating it is indeed interesting.

Why don’t you explain in detail how simple it is?
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Old Apr 19, 2022 | 10:01 PM
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I believe you just turn on the ignition without starting the car (foot off brake) and pull the manual parking brake release which is just under the headlight knob.
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