Do all Mercedes seem to run hot?

[Tikka]

Hi
As above, hot is relative.

We have a GM Astra with the Z16XEP Engine. The thermostat on these does not even open until 105c (221f). They operate around 109c (228f). The cooling fan kicks in around 113c (235f)

GM do not give a gauge but you can access the coolant temp' via a hidden menu on the centre display.

You need to keep a 50/50 coolant mix and make sure the system is tip top condition.

I also have a Jeep with the Mercedes OM642 Engine. The gauge sits reassuringly just a knacker below half. No idea what the temp is but it has warm heaters in winter and gives no grief in summer so I am happy living in ignorance.

 

[ARCOgraphite]

OP: I can just imagine people asking me why is the car running hot

What ? !

The things people worry or concern them selves with when they should be worrying about something important.

There is a red zone. Would not that be HOT. Plus everyone knows 100 deg C is boiling water at 1 ATM

I think Atikovi just slyly snuck in a "car for sale " ad

 

[djb]

BMW is typical of European design. They have used 'buffered' gauges since the 1990s. The gauges are stepper motors that are software operated. They report whatever results in the fewest customer questions and complaints.

Generally the temperature is Map controlled. The ECU decides the preferred operating temperature and changes the actuators toward that target. BMWs (and many others) have a fail-safe electrical thermostat. It's a traditional wax motor thermostat with a high opening point and an electrical heater in the core. The ECU heats the core to open the thermostat. That way the ECU maintain the desired temperature, but if the heating circuit fails the engine just runs (safely-ish) hot. Later they added ECU over-ride then full variable speed control to the electrical radiator fan.

 

[barryh]

The gauge in my Mercedes is the same with the 80C at half way but it runs at little higher at a very stable 90 C.

I'd be less happy if it was running at 80C which is too cool.

The handbook says anything up to 120C is normal in a high ambient with the engine under high load.

 

[Tikka]

Originally Posted by djb
BMW is typical of European design. They have used 'buffered' gauges since the 1990s. The gauges are stepper motors that are software operated. They report whatever results in the fewest customer questions and complaints.

Generally the temperature is Map controlled. The ECU decides the preferred operating temperature and changes the actuators toward that target. BMWs (and many others) have a fail-safe electrical thermostat. It's a traditional wax motor thermostat with a high opening point and an electrical heater in the core. The ECU heats the core to open the thermostat. That way the ECU maintain the desired temperature, but if the heating circuit fails the engine just runs (safely-ish) hot. Later they added ECU over-ride then full variable speed control to the electrical radiator fan.


Hi
This is how the euro GM Z16XEP works. The thermostat opens thermally like any wax filled one but at 105c. However the thermostat has a heating element that the Map can use to open the thermostat at 90c should it detect heavy engine loads and high revs.

 

[Touring5]

Originally Posted by Quattro Pete
Originally Posted by 92saturnsl2
I suspect many other vehicles are set up this way too.
Yup. If the needle doesn't sit exactly in the middle, customers come to the dealer/service dept with questions. So the easiest way to stop them from asking questions was to program in a dead range into the gauge.

Exactly right. On my E39 cooling system issues are probably the most common failure point, so awareness of the temp guage is essential (especially on the I-6 engine). That silly calibration makes it even more important to know that if the guage jumps up to 1 o'clock you'd better kill the engine to be safe.

The good thing is that the scaling/calibration of the temp guage can be modified with a little work using software like INPA or PAsoft. I don't know if similar products are out "in the wild" for Mercedes products or not.

 

[supton]

Originally Posted by djb
BMW is typical of European design. They have used 'buffered' gauges since the 1990s. The gauges are stepper motors that are software operated. They report whatever results in the fewest customer questions and complaints.

I find it annoying. I get why they do it, but... I thought heat wasn't doing so well in my Jetta, hooked up Scangauge, and found that the most it'd hit was 160F or so. T-stat had failed. But the gauge was reading fine. I guess that gage wasn't heavily filtered as much as outright lying--it was reading 190F from like 150 to who knows what.

 

[ChristianReske]

90°C is ragarded as perfect water Temperature here. BMW, VW, Audi, Merceds.... all run with 90°C.

Even my Honda S2000 has a bufferd temperature gauge. See the pics:

https://modifry.com/index.php?route=product/product&path=18_59&product_id=233

And yes, it was made beacuse people asked the dealer and mechanics (annoying) questions back when the temp gauges where non-bufferd.

 

[vavavroom]

The gauge clearly indicates when the coolant exceeds normal operating temperature,. The needle will be IN THE RED. How much more clear could the gauge be? Can you read an analog watch only if 12 points up? lol

 

[Duffyjr]

So I've read this thread a couple times and not sure what to think. So the car is not really over heating (looking at thread title), it's just the gauge is not centered or where the OP would like it to be.....

 

[atikovi]

Originally Posted by vavavroom
The gauge clearly indicates when the coolant exceeds normal operating temperature,. The needle will be IN THE RED. How much more clear could the gauge be? Can you read an analog watch only if 12 points up? lol


A car will run until the fuel gauge points to E. By that analogy you would you not worry about filling up with gas until it's a hair before E.

 

[vavavroom]

Originally Posted by atikovi
Originally Posted by vavavroom
The gauge clearly indicates when the coolant exceeds normal operating temperature,. The needle will be IN THE RED. How much more clear could the gauge be? Can you read an analog watch only if 12 points up? lol


A car will run until the fuel gauge points to E. By that analogy you would you not worry about filling up with gas until it's a hair before E.


That's a faulty analogy. A coolant gauge does not indicate range of an overheating engine.

 

[atikovi]

Originally Posted by vavavroom
Originally Posted by atikovi
Originally Posted by vavavroom
The gauge clearly indicates when the coolant exceeds normal operating temperature,. The needle will be IN THE RED. How much more clear could the gauge be? Can you read an analog watch only if 12 points up? lol


A car will run until the fuel gauge points to E. By that analogy you would you not worry about filling up with gas until it's a hair before E.


That's a faulty analogy. A coolant gauge does not indicate range of an overheating engine.


Why sure it does. That's what the red band shows. Overheating starts after the 120 mark where it's slightly overheated, up to maybe 130 where it's very overheated.

 

[Wolf359]

Originally Posted by atikovi
Originally Posted by vavavroom
Originally Posted by atikovi
Originally Posted by vavavroom
The gauge clearly indicates when the coolant exceeds normal operating temperature,. The needle will be IN THE RED. How much more clear could the gauge be? Can you read an analog watch only if 12 points up? lol


A car will run until the fuel gauge points to E. By that analogy you would you not worry about filling up with gas until it's a hair before E.


That's a faulty analogy. A coolant gauge does not indicate range of an overheating engine.


Why sure it does. That's what the red band shows. Overheating starts after the 120 mark where it's slightly overheated, up to maybe 130 where it's very overheated.


Sorry but I'm siding with others on this. You just have to know how to read a gauge. Now you're trying to say there's some gauge symmetry which is something completely different.

https://en.wikipedia.org/wiki/Gauge_symmetry_(mathematics)

 

[atikovi]

Gauges should give you information in a consistent manner such that the normal operating parameter is at the center point of the scale. Race cars often have the pointer point straight up for the normal parameters of water temperature, oil pressure, voltage, redline so the driver can tell at a quick glance that all is good.

 

[SteveSRT8]

Originally Posted by atikovi
Gauges should give you information in a consistent manner such that the normal operating parameter is at the center point of the scale. Race cars often have the pointer point straight up for the normal parameters of water temperature, oil pressure, voltage, redline so the driver can tell at a quick glance that all is good.


Exactly. Every SCCA wannabe in my childhood clocked the gauges so that they pointed to the same place when readings were normal.

Every real driver wants real gauges. My TR-4 was so real that one day it spewed hot oil all over the place! I got a very accurate oil temperature reading via my burnt-skin-o-meter!