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I got benz-ninja to code the AMG menu so I can monitor oil/coolant temps. I understand these temp sensors are not exactly accurate but still do a decent job. I have unplugged oil solenoid, run LM 5W40 with a 250ml shot of M1 5W50 @ 2000 miles and installed a new thermostat.
What I am seeing is sometimes coolant temps read about 187F constant and sometimes its 221F constant with oil temp close to same. If I run it above 3500rpm, temps will start dropping from 221F down to the 187F range fast. That normal? Why sometimes is it hanging at 187F and sometimes hanging at 221F until I get on it? I would not think there should be that big of a swing in temps. Seems that the thermostat might be modulating under normal operating conditions (below 3500RPM) and fully opens upon seeing high RPM (Above 3500RPM). If it is modulating at low RPM why is it showing high temps sometimes and lower temps other times? Seems all over the place.
Edit: To clarify, I did pull a vacuum on the coolant system, let sit for 60 seconds with no vacuum loss before filling system. Same drive every day, 10 miles/15 minutes. Today, went home for lunch, never got above 176F. Coming back hit 186F. This mornings drive in hit 221F.
Last edited by wheatswake; Jun 24, 2024 at 02:03 PM.
I got benz-ninja to code the AMG menu so I can monitor oil/coolant temps.
I understand these temp sensors are not exactly accurate but still do a decent job.
I have unplugged oil solenoid, run LM 5W40 with a 250ml shot of M1 5W50 @ 2000 miles and installed a new thermostat.
What I am seeing is sometimes coolant temps read about 187F constant and sometimes its 221F constant with oil temp close to same. If I run it above 3500rpm, temps will start dropping from 221F down to the 187F range fast. That normal? Why sometimes is it hanging at 187F and sometimes hanging at 221F until I get on it? I would not think there should be that big of a swing in temps.
Seems that the thermostat might be modulating under normal operating conditions (below 3500RPM) and fully opens upon seeing high RPM (Above 3500RPM). If it is modulating at low RPM why is it showing high temps sometimes and lower temps other times? Seems all over the place.
Edit: To clarify, I did pull a vacuum on the coolant system, let sit for 60 seconds with no vacuum loss before filling system.
Same drive every day, 10 miles/15 minutes. Today, went home for lunch, never got above 176F. Coming back hit 186F. This mornings drive in hit 221F.
I've just seen your message and think you're in a pretty good spot:
-- LM-5W40 + 250mL @2000.MI = MOD-2.1
-- New coolant Tstat installed.
You're seeing inconsistent temps that look a bit unsettling.
dynamic engine temps
The dashboard gauges display a doctored temps to keep drivers at ease...
The ECU managed coolant Tstat indeed has a mapped response built-in. It has to reach a high before it will swing low.
So when you combine all that the coolant swings look concerning BUT are not.
Read the engine coolant sensor itself directly not the translated number.
Your new coolant tstat gives you full confidence tstat is not sticking like an old cooked unit.
Your MOD-2.1 removes your engine heat perfectly.
You should witness your oil holding its color and NOT burning black. The ultimate proof of favorable engine temps.
Last edited by CaliBenzDriver; Jun 26, 2024 at 06:12 PM.
Seems pretty normal to me. The fan doesn't kick on until it's basically overheating, as you can see in the fan speed control map for your car below. The % is the duty cycle, basically the fans speed from 0-100%. 225 to >230 is where the fan will let it go, unless you have some vehicle speed to get air flowing through it. On the freeway, and 0% fan, mine will drop as you described, even into the 170's, including when it's hot out.
To fix what I consider overheating, I adjusted those fan settings in the pix to ~30F cooler. Now it usually stays under 200 all the time. The last few days were pretty hot, and it stayed <200, but it did go to 205 for about 5 seconds while at a light, baking in the 1pm sun. With the oem settings that would've been >230.
A few drops of very slightly thicker oil won't do anything, and certainly won't help cool it. It wouldn't even bring the viscosity back up to when the oil was new. If you want to add some thicker oil, get some oil that's actually thicker. Like Lucas stabilizer at 110W Still won't make much difference only adding 250cc, but a quart will help. Thinner oil removes heat better, and generates less heat in the first place, but you won't notice the difference. You want thicker oil because you want the eng to last. Imo nobody living in a desert should be running 5W in the first place. I'm quite a bit north of you and I won't bring 5W anywhere near the car, because I don't want to traumatize it. I use more like 25W-40, and my next fill will be a little thicker. Remember, light oils are dictated by the EPA, who would prefer your eng die asap.
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Still won't make much difference only adding 250cc, but a quart will help. Thinner oil removes heat better, and generates less heat in the first place, but you won't notice the difference. You want thicker oil because you want the eng to last. Imo nobody living in a desert should be running 5W in the first place. I'm quite a bit north of you and I won't bring 5W anywhere near the car, because I don't want to traumatize it. I use more like 25W-40, and my next fill will be a little thicker. Remember, light oils are dictated by the EPA, who would prefer your eng die asap.
