Mercedes-Benz Forum banner

Engine operating temperature?

89K views 38 replies 16 participants last post by  khomer2 
#1 · (Edited)
Quick question - (98 C230)

it's starting to warm up a bit (10-15c (50-60f)) and I've noticed my engine temperature gauge rising above the midway point (80c), sometimes reaching midway to the next line (approx 90c) - It does go back to 80c when I start driving & reach an open stretch. My engine temperature constantly stayed at 80c during the winter (-10 to -25c).

Is that "normal" for the temperature gauge to actually move or should I be concerned - My previous BMW's engine temp (which was a nightmare in terms of cooling issues :crybaby2: ) stayed in the middle unless something was wrong.

Also - when should the auxiliary fan (the fan behind the radiator?) kick in? I've kind of checked to see if it was on a few times (with ac on or off) and it was never running...?

Thanks in advance everyone!

**edit**
fan behind the radiator is running..
 
#2 ·
well most of the time my temperature stays between the 80 and the next mark which if i remember right is 100. the aux fans will kick on at 100C or a certain pressure. if your temperature rises while sitting in traffic for a long time, then i would say its normal. if it rises to 100 at any other time then i would maybe start looking for whats wrong.
 
#3 · (Edited)
Which Fan behind the radiator?

Are you saying that the mechanical (Viscus Clutch Fan) is not spinning when the motor is running? When the A/C is on, Engine Hot, ALL the Fans (Electric in front of the radiator) AND the Viscus Clutch fan behind the Rad. should at least be spinning if not spinning hard. If you turn on the A/C and the compressor is running I believe the electric fans should be running too. There is a relay and a temp control switch in charge of turning these on. Check your fuse box to start.

Most of the 4 cylinder cars in this section usually run pretty stable in temp under most conditions at just over 80c.

Good Luck!:thumbsup:

C as in 220
 
#6 ·
What's the deal?

I sure would like someone that really knows to explain why some cars (My C-220) stays ROCK SOLID right above 80c in all but the most extreme conditions, while others fluctuate like 00_230_K and t-im just described.

All the cars and pick-ups I have owned over the years have remained stable with regards to Thermostat opening temp. unless in extreme heat or something was going wrong.:confused::confused::confused:

Good Luck!:thumbsup:

C as in 220
 
#7 ·
If it helps to find an average, my car is a '99 c230K and it stays locked in at 80 unless it's stuck in stop and go traffic on a very hot day but even then it barely budges above.
 
#8 · (Edited)
well cj depending, maybe the supercharged benzes has something to do with it, im not saying it is, but can it be put as a possiblity ? anywho if mine is not operating properly i would like to know but its been like this for 2 years now since i bought it , i tested the coolant today it was protected to the maximum on the tester so i guess the collant is still good
 
#9 ·
Mine stays at 87 Celsius all the time aswell, but it used to fluctuate before I changed the Thermostat, now its rock solid at 87 Celsius. Make sure yours has been changed, it should be changed when you flush the coolant every 2-3 years.
 
#10 ·
All of my Merc's stay between 80° and 100° (just below the 100° actually)... this is completely normal... the reason you notice the fluctuation is that Mercedes gives "actual" readings, unlike most cars (like my old Honda) that would stay rock steady just below mid point unless there was a problem, then it would move... car makers do this so people don't panic if their temp needle moves... BMW's stay rock steady in the center unless there is a problem.

But yes, have your coolant flushed if it hasn't been done in ~2 years... I am actually making my appt right now for coolant flush and transmission service.
 
#18 ·
But yes, have your coolant flushed if it hasn't been done in ~2 years... I am actually making my appt right now for coolant flush and transmission service.
Do you go to Sig for service? How much for just the coolant flush? Thanks!
 
#12 ·
wow new rad, really man whats this coming to, ur scared of temp gauge fluctuating , getting new rad , its like throwing money away , unless u got some to spend, don't fuck with it if it aint broke, its its fixable fix before replacement, most of our benzes seem to be moving around 80-100 so it seem normal , its a extremely rare case where u have to replace the rad on a benzo and expensive too, think about it try the termostat first
 
#14 ·
00_230_K,

i already replaced waterpump and thermostat.

throwing money away? i dont think so. i have the originial radiator from 98. for $200 it is inexpensive.

extremely rare to replace a rad? uuuhh i think an 11 y/o radiator is due to be changed.

i bet my temp stabilizes afterwards.
 
#15 ·
well you just might prove me wrong, unlikely tho, these are BEHR rads from what i know they last the lifetime of the vehicle, its not your typical chevy rad , did u check your fans are they engaging on time, are they engaging at all? are u using proper coolant?, , my temp flucuates its perfectly fine tho tho rad is good and everything else seems to be good, and , as mentioned by another member maybe our temp reading are more precise than in other vehicles and show actual readings , take for example my previous integra, i push her at the dragstrip nonstop, the temp gauge is in the same spot as if i were cruising 60mph on the freeeway, where as on the highway it should be much less , well it kinda makes sense, but its a probablity tho , good luck with your rad replacement and keep us updated
 
#19 ·
I do go to Sig... but I am having Rasmussen do the flush since Sig isn't open on Saturday's... Rasmussen quoted me $100 for the flush. I am putting off the transmission service for a bit (I am only at 93k miles) as I have another issue that has cropped up with my fresh-air flap and I am not sure how much that is going to run to correct.
 
#20 ·
Thermostats

A thermostat is a valve that opens a certain amount based on the temperature of the liquid it's immersed in. What's supposed to happen in a car is when you start it cold, the thermostat is immersed in ambient temperature coolant, so unless you live somewhere that's really hot, the thermostat is completely closed. Sometimes thermostats have a small bleeder hole in them so that when you drain the coolant it will allow bubbles to enter the engine which allows all the coolant to drain out. If there is a bleeder hole it will allow a very small amount of coolant flow when the engine is cold. The water pump is applying pressure but the thermostat controls how much flow there is. The closed thermostat helps the engine warm up to normal operating temperature. As the coolant temperature in the engine rises, the thermostat starts to open. It's designed to keep the engine coolant temperature at a certain minimum temperature. Hence the different temperature ratings of thermostats. As thermostats and the coolant age, deposits are left on the thermostat which restrict its movement. Left long enough, the thermostat will eventually stick at some position. If it sticks closed, the engine will overheat which can cause serious expensive damage. If it sticks wide open, the engine will not warm up to operating temperature and the heater won't blow warm air. These effects are also affected by the ambient air temperature. If a thermostat sticks partially open, it will act like a restrictive orifice, which allows a certain amount of flow at a certain pressure. The engine temperature will be more affected by the ambient air temperature. It could be stuck such that the engine takes a long time or never actually reaches normal operating temp when the ambient air temperature is cold and the engine runs hotter than normal or even overheats when the air temperature is hot. Some normal fluctuation is normal. That's why there are auxiliary electric cooling fans on radiators. As long as the engine warms up to the thermostat temp rating within a few minutes and it doesn't overheat, the thermostat is working as it's supposed to. A thermostat is a very inexpensive easy to replace part. It your car is experiencing any of the symptoms of a stuck or stubborn thermostat I recommend that it be the first thing you replace. New coolant should always be used when installing a new thermostat, especially if you can see corrosion buildup on the old thermostat. You can also easily check the operation of a thermostat(old or new) by simply immersing it in a boiler of cold water along with a thermometer, turn on the heat and watch the temperature of when it begins to open and at what temperature it gets completely open. Unless I have a coolant leak, I wouldn't consider replacing any other component of a cooling system without first ruling out the thermostat as the problem. Sorry to be so long winded but I wanted to touch all the bases.
 
#22 ·
A thermostat is a valve that opens a certain amount based on the temperature of the liquid it's immersed in. What's supposed to happen in a car is when you start it cold, the thermostat is immersed in ambient temperature coolant, so unless you live somewhere that's really hot, the thermostat is completely closed. Sometimes thermostats have a small bleeder hole in them so that when you drain the coolant it will allow bubbles to enter the engine which allows all the coolant to drain out. If there is a bleeder hole it will allow a very small amount of coolant flow when the engine is cold. The water pump is applying pressure but the thermostat controls how much flow there is. The closed thermostat helps the engine warm up to normal operating temperature. As the coolant temperature in the engine rises, the thermostat starts to open. It's designed to keep the engine coolant temperature at a certain minimum temperature. Hence the different temperature ratings of thermostats. As thermostats and the coolant age, deposits are left on the thermostat which restrict its movement. Left long enough, the thermostat will eventually stick at some position. If it sticks closed, the engine will overheat which can cause serious expensive damage. If it sticks wide open, the engine will not warm up to operating temperature and the heater won't blow warm air. These effects are also affected by the ambient air temperature. If a thermostat sticks partially open, it will act like a restrictive orifice, which allows a certain amount of flow at a certain pressure. The engine temperature will be more affected by the ambient air temperature. It could be stuck such that the engine takes a long time or never actually reaches normal operating temp when the ambient air temperature is cold and the engine runs hotter than normal or even overheats when the air temperature is hot. Some normal fluctuation is normal. That's why there are auxiliary electric cooling fans on radiators. As long as the engine warms up to the thermostat temp rating within a few minutes and it doesn't overheat, the thermostat is working as it's supposed to. A thermostat is a very inexpensive easy to replace part. It your car is experiencing any of the symptoms of a stuck or stubborn thermostat I recommend that it be the first thing you replace. New coolant should always be used when installing a new thermostat, especially if you can see corrosion buildup on the old thermostat. You can also easily check the operation of a thermostat(old or new) by simply immersing it in a boiler of cold water along with a thermometer, turn on the heat and watch the temperature of when it begins to open and at what temperature it gets completely open. Unless I have a coolant leak, I wouldn't consider replacing any other component of a cooling system without first ruling out the thermostat as the problem. Sorry to be so long winded but I wanted to touch all the bases.
Holy crap that's a mouthful. Informative though.

And yeah, the temp guage in my car also hits between 80-100 on warm days. On cold days it doesnt really go above 80.
 
#23 ·
W202 C230K and W202 C220

Hello all, this seems like an older thread but I will post anyway...

I have two W202s, a '00 C230K and a '95 C220. Today in southern california, it was a but warm outside (87F+) and i noticed that the C230K does indeed hover around the 100 degree mark especially in slow traffic or idle. On the freeway, it dropped to the usual 80s...
Vehicle Car Gauge Auto part Speedometer

Then I took out the C220 and that thing remained below 80 like a rock. Not even a small flicker...

Has anyone been able to confirm the effect of superchargers on these M111s? I understand this is a very common / normal thing that most people are experiencing but it is still bothering me somehow :(

Thanks in advance.
 
#24 ·
Actually you seem to be having a problem with the C220. The correct operating temperature is 87 degrees. It sounds like your thermostat may be sticking open. If an engine operates below operating temp, it will not be operating at its most highest efficiency. I would suggest you start with that. The c230k seems to be OK, but only if you had the A/C on. My C220 hits 95C when in traffic in 30C + weather (and it will fall back down to around 90 when the A/C aux fans kick in). If your c230k hits 95 without the A/C, then there is a possible issue (the thermostat might be not opening enough).

It's also possible your C220 has a 78degree thermostat installed, but that is not the right thermostat! The correct one is 87 degrees.
 
#25 ·
I will definitely check the thermostats on both. I definitely did not turn the AC on with both the cars today because i just had the window down. Bring AC into the question might shed more light. I shall report back soon.

The C220 is pretty bad, I am keeping it as a potential project car.

Good insight. Thank you so much!
 
#29 ·
Yes it was definitely without the AC and that is why I decided to post this. Next few days are supposed to be cooler here so I wont be able to redo it...I will come back and update you guys when it gets warmer again.

BTW thank you patman1 for that awesome flowchart. Lets hope the issue is one of the easier blocks...
 
#30 ·
So it was not as hot today, but warm enough for the temperature to reach approximately the same 95deg+ levels like the pic i posted. I was in super slow traffic so i turned the AC on to test. The temp didn't rise very much, definitely didn't even hit the 100 mark.

I'll still keep an eye on this on much warmer days because nothing is concluded for me...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top