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1998 Mercedes C240 Elegance Auto (UK)
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Discussion Starter #1
Hi all (1998 c240 2.4 v6, uk)

I've had the misfortune of getting hit by several different problems all at once.
I have included vids and pictures to make explaining easier. They may or may not be related. Hopefully this thread should clarify that.

1) Recently the radiator fans decided to always go on full blast as soon as the car is started, (ie when the key is in the 'on' position and when the cars running). They turn of when car is turned off.

Trying to get to the bottom of this on this thread:
http://www.benzworld.org/forums/w202-c-class/1666248-98-c240-radiator-fans-always-very.html#post5366482

Here is what its like in idle from a cold start



2) The engine temp gauge is showing above the 80 middle mark, even if the cars been standing all night. The car has plenty of anti freeze (no leeks, no decrease in expansion tank). This happened soon after the fan problem above. The gauge is very jumpy, as you can see it shoots to the 120 mark from a cold start and constantly moves around there. (see vid of problem 3)

3) Finally, :crybaby2: The car fires up after a 'longer than usual' crank, idles and then dies.

(vid: notice it stalls by itself, and notice mad temp gauge, done from a cold start)



I am completely at a loss. It had the crank position sensor changed literally less than 100 miles ago. Can spark plugs and coil packs be an issue? They have not been touched in a while.

ANY pointers would be greatly appreciated people.
 

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'01-E320 & 02-ST2
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31,631 Posts
I'm wondering if the work on the CPS perhaps chafed a wire to (or damaged) the coolant temp sensor? Or perhaps it is just failing as an unhappy coincidence. But I have a feeling that's going to be the issue; it's sending faulty information to the ECU which is triggering the fans to try and "cool things down" and when it's hot enough it just shuts it off.

So I'd start with inspecting the CTS and the wiring to it.

Good luck.
 

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1998 Mercedes C240 Elegance Auto (UK)
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25 Posts
Discussion Starter #3
Thanks for the info mate. Could you tell me whereabouts this coolant temp sensor is on this engine?
 

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'01-E320 & 02-ST2
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Thanks for the info mate. Could you tell me whereabouts this coolant temp sensor is on this engine?
If you have the V6 M112 engine, I've attached a picture that represents it.

The sensor itself looks like this:



The left side of that is inside the engine, just the black plastic top and larger metal ring sticks out. Obviously there are wires and a harness clip going to it. If I had my car nearby I'd post a pic for you, but this is the best I can do right now. You might want to start by just unplugging it and being sure the connection is clean and dry and free of corrosion, and check the wires to be sure they aren't fouled.

Good luck.
 

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Registered
1998 Mercedes C240 Elegance Auto (UK)
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25 Posts
Discussion Starter #5
excellent, many thanks for that! i'll have a snoop around today
 

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Registered
1998 Mercedes C240 Elegance Auto (UK)
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25 Posts
Discussion Starter #6
UPDATE-

my local mechanic changed the spark plugs and oil/filter. The car starts ok on the dot. It is a bit lumpy on idle and if the maf is disconnected, this lumpiness goes away. I was told to get a new maf as this is a sign of one dying.

But no more crazy rad fan or temp gauge!
 
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