That looks pretty normal. Hot days in heavy traffic and it will go up

 

My car is CLK 500. In the cool day, it is about 80 C. For summer time with air-con on, it went up to 100 C. The reading on your gage is about 90 C and it is normal.

 

not that I know what the “right” range is but I start to look more carefully if it goes past the next line. if it keeps going I get worried but if it hovers around the line I feel it’s good. If yours stays like the way it looks in your picture you should feel good about that, imo

 

do we know what number the next line is?

 

Pretty much looks right.
I run a 87C thermostat....gotta read between the lines. Literally.

 

Looks spot on to me. I'd guess 87C.

R

 

What’s the correct range for operating?

Generally speaking, the operating range ends at the redline.

 

 

RIGHT Marcel! That is is what I posted in post #8, except no pretty picture

 

Sorry that’s what I meant to say the midway between 80 and120 was the 100 hash snd midway between those two was 90.

 

Looks good. Mine is always at this or a few degrees higher if in traffic.

 

I got an '83 380SL couple of weeks ago, so I am still learning how it should behave.

First minutes of driving, during warmup, my temp goes up way above 100, scarily close to 120.
Then suddenly it quickly drops to the horizontal level between 80 and 100, and stays there for the ride.
I am thinking that my thermostat is working OK as it stays on the correct level.
But is the high temp during warmup normal? And if not, where should I start looking?

 

First minutes of driving, during warmup, my temp goes up way above 100, scarily close to 120.
Then suddenly it quickly drops to the horizontal level between 80 and 100, and stays there for the ride.
I am thinking that my thermostat is working OK as it stays on the correct level.
But is the high temp during warmup normal? And if not, where should I start looking?

Perfectly normal. The gauge is showing temperature at the sending unit before the thermostat opens and then when it is open and the coolant is flowing freely. Everything appears to be working as intended. Go worry about something else,

 

That sounds like a slow or late opening thermostat to me. I would recommend starting with replacing the thermostat. A citrus flush of the system would also be a good idea...that is a maintenance item that often gets neglected.

Cheers
dankly

 

That sounds like a slow or late opening thermostat to me. I would recommend starting with replacing the thermostat. A citrus flush of the system would also be a good idea...that is a maintenance item that often gets neglected.
...

Thanks dankly1. Good suggestion to flush the system first. I'll do that and check the thermostat.

 

The initial rise in reported temperature is quite usual (mine has been doing it for 30+ years) and there is even a service bulletin which recommends drilling a small hole in the rim of the thermostat to allow a small flow of coolant even when the thermostat is fully closed so as to lessen the rise and to silence demanding customers.

 

The initial rise in reported temperature is quite usual (mine has been doing it for 30+ years) and there is even a service bulletin which recommends drilling a small hole in the rim of the thermostat to allow a small flow of coolant even when the thermostat is fully closed so as to lessen the rise and to silence demanding customers.

Could you post a copy of that service bulletin? It would be interesting to read just what it says. Was it for a 107 or your 300SL?

I have read an article from a diesel site that suggests drilling a hole could be done as a last resort to overcome overheating, but that then results in slow warm up. Even Diesel giant says: "Now understand that this modification is not a Mercedes fix, it is my fix.". He did it in attempt to overcome continued overheating, not just an initial spike.

If some cars have this problem, but most do not? What could be the cause?

• incorrect thermostat?
• visco fan delay,
• different climate?
• sensor problem?

There are a number of different thermostats available with different temperature ratings. Installing correct one for car might be a start.

Visco fan can be checked to see that it comes on & is functioning correctly. Also covered in FSM. I recall there being different types depending on engine and model year.

 

It looks like this type of discussion has been on BW in past ! I don't own a 380SL and don't know what could be different about it compared with a 350/450SL. But guys in this discussion seem to think so

Need help To Modify thermostat

83' 380SL: I read but now cannot located a procedure where you should modify a new thermostat by drilling holes. Can anyone expand on this as I cannot locate the article? thanks a bunch for your help.

www.benzworld.org

I found this discussion interesting, just from a technical viewpoint because of my engineering background. But no first hand experience of solving temperature spikes, so will leave it at that

 

My old M110 heats up gradually and stops just above the 80 line and stays there.

Going up the Rocky mountains on a summer day...it starts to climb a bit.

Ease off or on the downhill...back to normal.

No AC in The PIG.

 

How do you read this? Obviously in Celsius. What’s the correct range for operating? I just had my thermostat replaced, radiator flushed, belts checked, and it’s running cooler.

View attachment 2722390

I have an ML 350 W163. Thats where my gauge sits also, engine has less than 60k miles ,runs perfectly

 

Isn't this the R/C107 sub-forum?

Seems like the subject of this particular thread has attracted MB owners with many different models! This may be caused by that NEW button top right. Doesn't keep discussions within the sub-forum.

Not to say that some of the comments haven't been relevant or useful. MB models of our vintage do have many things in common.

 

How do you read this? Obviously in Celsius. What’s the correct range for operating? I just had my thermostat replaced, radiator flushed, belts checked, and it’s running cooler.

View attachment 2722390

Best explanation I have see so I re-posted it from another web site

"The thermostat on the M119 doesn't fully open until 94 °C (201 °F), and the cooling fan's viscous clutch does not engage until 92 to 100 °C (198 to 212 °F) air is flowing over it (meaning the coolant temperature at the sensor is likely 5 to 10 °C hotter than that).
So, 80 to 100° C is the normal range depending on vehicle and engine speed and ambient temperatures--in very hot ambient temps (we hit 104° F here the other day) the coolant may reach 105° C while stopped in traffic. Without AC on the electric fans will not kick in until the coolant reaches 107° C, and will stop once it cools to 100.

Most newer cars have coolant temperature gauges with non-linear and dampened characteristics that keep the pointer more or less in the center of the range as long as the coolant temperature is within the "normal" range (80 to 120° C on most cars).

Our cars do not do this but instead show the actual temperature as it moves through the normal range--I.e. is is accurate. "

 

The most fuel-efficient coolant temperature is at the hot end of the operating range.