Coolant temperature on diesel

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anparkinson

New Member
Joined
Jul 4, 2020
Messages
17
Location
Tn339qa
Car
CLS 320
What is normal running temperature for a 320 CDI 642 V6.

Mine's a 2009 CLS and never goes over 80. Seems
 
Mine gets to 90 and stays there .I remember in days of yore mechanics used to test them by putting them in boiling water to see if it would open
 
90 as above.
 
85 / 86 is right enough.
I wouldn't write off a stat at 80, it depends on your drive style.
If it reaches temp on a run but drops a fair bit on a down hill cruise then I'd write it off.
Torque on your smart phone with a BT transmitter is good for monitoring as accurate as the ECU will let you. You don't know if the sender is sending the correct and accurate temp.
 
On two E350 OM642s I know well, they sit below 90, at around 88.

As Markjay said, you need a new thermostat. It's not a difficult DIY, if you're into that kind of thing.

Unfortunately it's quite an expensive part on the 642...
 
On the several diesel MB cars we own or have owned, the temp normally sits slightly above the 80 mark. On a hot day stuck in start-stop traffic on the motorway, it would normally edge upwards 90.

On one occasion the temp light came on in our W210 320CDI near Birmingham on the M6 and the temp gauge was well over 100 (probably nearer the 120 mark). That resulted in a thermostat replacement. Also on the same car, when we first bought the car the temperature gauge never went much above 60 and this was fixed with the thermostat being replaced (with a noticeable improvement to the mpg on the 320CDI).
 

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