Is there a 'normal' temperature range? C220 CDI

jcswright

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Hello

I recently bought a 2006 C220 CDI, and I'd like some advice about the running temperature. On all the cars I've driven in the last few years the temperature gauge has gone to about 90 degrees and then stayed there or thereabouts. It might go up a bit stuck in traffic on a hot day, or down a bit rolling down a hill on a cold day, but it doesn't change much (as much as you can tell from the gauge, anyway).

My new (to me) car varies between about 65 and 90 degrees (I know the gauge isn't necessarily accurate but it's an indicator?) depending on what the driving is like. At one point it was so low after half an hour of driving that I took a photograph of it.

It seemed odd to me that a modern car should sometimes run that cool after it's warmed up, so I called the dealer (it's still under warranty) and they told me that was normal.

I should leave it at that, and I feel very awkward questioning the people who actually know what they're talking about, but on the other hand this still doesn't feel right to me - can someone please reassure me that it's normal for Mercedes diesels to have a nearly 30 degree variation in their running temperature during summer? Perhaps the sensor is in a different place to other cars?
 

turbopete

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mine once warmed up sits around the 85c mark +/- 5c

if it drops below around 80c when its hot, you will probably need the thermostat replaced. only about £45 for the part from MB
 

Alex Crow

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You have a failing thermostat, a common issue with the CDI engines (being very efficient, little heat is generated under light loads, meaning the 'stat has a harder job closing fully enough to keep temps up).
Replace the 'stat and all will be fine (running between 85 and 90).
 

survey

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My old 2008 C220 cdi used to hold at around 90degrees.
My newer E coupe 250cdi I am sure used to go straight up to 90 degrees. More recently it has gone up to 80 then hunts up and down between 75 and 80, eventually going to 90 degrees and even then may drop back a bit towards 80. Car has been in for diagnostics and I am told it is fine. MB Technical tells me that 80-100 is 'normal'. Not sure myself as I'm sure there was never this delay before getting to 90.
 

television

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This applies to all cars, both diesel and petrol, if the engine is running much below 80c the heater will never feel warm in the winter, 85 to 90 is fine
 

turbopete

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More recently it has gone up to 80 then hunts up and down between 75 and 80,

this could be the thermostat opening and closing until all the coolant is up to temp.
coolant temp will fluctuate a little regardless, depending on engine demand, airflow, etc
 
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jcswright

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OK - thank you everyone, but the plot thickens a little...

Before I saw all these replies, I also called a local independent Mercedes specialist and told them pretty much exactly what I wrote in my initial post.

They said that this is normal behaviour and nothing to worry about.

Why do the two garages I've spoken to disagree with pretty much every answer I've got here?

I promise I'm not trying to stir anything up, I am just very confused now.
 
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Naraic

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Don't be confused. When a thermostat is working as it should the temp of the engine will be pretty much constant...new stat as above. The gauges are very accurate so what you describe is a failing stat.
 
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television

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I could understand some fluctuations on the new blue engines when you see how complicated the cooling systems are.
 

davidsw

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If it runs at 65 now what will it run at in winter ....you'll be freezing !!!!
 

tode

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The thermostas on Mercedes HGVs used to have the operatibg temp. stamped on them. The 'standard' was 87° iirc, but you could also get higher and lower temps.

Are the (modern) car thermostats similar?
 

Alex Crow

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If it runs at 65 now what will it run at in winter ....you'll be freezing !!!!

Indeed, we usually reserve these threads for winter!
 
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jcswright

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OK - thank you everyone for your advice.

I think I will just ask them to replace it regardless, and we'll see what happens.

Will report back.
 
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EmilysDad

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OK - thank you everyone for your advice.

I think I will just ask them to replace it regardless, and we'll see what happens.

Will report back.

Start the car from cold. Place your hand on the top radiator hose & see hw it gets hot. It should stay cold & then get hot in one go as the 'stat opens, if the 'stat is stuck open (as yours seems like it is) then the rad hose will get slowly warm/hot as the engine gets to temp.
 
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jcswright

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Hello

Sorry for the delay following up with this.

I took the car into my local dealer, who told me the fluctuations were normal - so I thought I'd wait until it got colder before I went into this any further.

Now that it's colder, the gauge never gets above about 80, and yesterday it was at 60 after I'd driven 10 miles. Also my mpg is lousy.

I've taken everyone's advice into account, the top hose does warm up slowly with the engine - but don't thermostats have a small bleed-hole in them anyway? I'm not sure I was able to determine much from that test I'm afraid.

Is there anyone reading this who has the same car (W203 C220 CDI) who knows what the gauge should do? I'm looking for a reply from an owner who can say theirs varies, or sticks at 90, or has experience of before/after the thermostat being changed. I've got plenty of "car" experience, but if the C220 has the sender in an unusual place, or something like that, then I wouldn't be sure my past experience is anything to go by...

Thank you!
 

survey

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Hello

Sorry for the delay following up with this.

I took the car into my local dealer, who told me the fluctuations were normal - so I thought I'd wait until it got colder before I went into this any further.

Now that it's colder, the gauge never gets above about 80, and yesterday it was at 60 after I'd driven 10 miles. Also my mpg is lousy.

I've taken everyone's advice into account, the top hose does warm up slowly with the engine - but don't thermostats have a small bleed-hole in them anyway? I'm not sure I was able to determine much from that test I'm afraid.

Is there anyone reading this who has the same car (W203 C220 CDI) who knows what the gauge should do? I'm looking for a reply from an owner who can say theirs varies, or sticks at 90, or has experience of before/after the thermostat being changed. I've got plenty of "car" experience, but if the C220 has the sender in an unusual place, or something like that, then I wouldn't be sure my past experience is anything to go by...

Thank you!

My opinion is that your thermostat is faulty. If you look back at my posting on this thread - MB Technical thought it may be a problem, MB franchise said it was OK. Certainly during the summer, my thermostat did 'hunt' before eventually settling at 90. Now with colder weather it does go straight up to 90 (eventually, as thesse engines take forever to warm up).
 
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jmoser

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Happened on my S203 C270 CDI a few months back; temp never exceeded 70C.

Fault was indeed thermostat - the garage showed me how knackered it was; since replacement temp has been a constant 90-95C.
 

robparker

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Shadowing all above comments, my e220cdi was running at 60c or so, fitted a new stat a week ago now it quickly warms up to 95c and stays there.

For the sake of a few quid, just replace the t-stat!!!
 
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toby1

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So after three months you still haven't replaced the thermostat? Curious
 
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jcswright

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Not that curious. Mercedes told me it was fine, so what am I supposed to do? For someone who doesn't know as much as you do about these things it's not as easy as you might think.

That said, I wouldn't have come here if I didn't think this community could help - and it has.

I got what I needed from the forum, which was a solid second opinion telling me I wasn't crazy, but I didn't get anything that I could present to Mercedes - it's still me saying "I think it's broken" and them saying "no it's fine". Also, me saying "I've heard from a guy whose car doesn't do this" doesn't cut much ice with the service department.

So, based on the responses here I thought I'd leave it until the colder months when it'll become more obvious, which is has, and now I'm waiting for a call back from Mercedes. I'll let you know what happens.

(I can't replace the thermostat myself, so it's not really 'just a few quid' to replace something that might not be broken. I'm happy (within reason!) to spend money on maintenance, but on this occasion if it's faulty, it'll be a repair under warranty.)
 
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