Engine never reaching 90C, high rev

Riva811

Active Member
Joined
Jan 7, 2018
Messages
604
Location
London
Car
CL500 Blueefficiency
Hello, we have this W212 that has high revs and the temperature never goes beyond 75 - or at least thats what the gauge says. So I am wondering if they are interconnected issues and whether it could be a simple sensor about to go wrong issue? The car was recently diagnosed using SD4 with no issues discovered. I also run my MB V2.0 prior to SD4 and the ECU returns no error codes at all.
 

rf065

MB Enthusiast
Joined
Jun 8, 2007
Messages
4,225
Location
Grossbritannien
Car
SLC300 - C250d Estate 4 Matic & Z900rs
I would change the thermostat and the temp should be fixed, then see what it's like.
 

exvolvoman

Active Member
Joined
Jan 25, 2017
Messages
238
Location
Mid Wales
Car
2004 C180k Estate & Volvo V70 T5
+1 for thermostat...usually the first and most obvious reason for running too cool, which will also upset the ECU, use more fuel etc.
If it still shows cool maybe check/change coolant temp. sensor
 

Teego

Active Member
Joined
Feb 2, 2018
Messages
947
Location
Derbyshire
Car
CLS55 AMG
+1 on thermostat but before going further and more expensive get a thermometer and check actual temperature.
 
OP
OP
Riva811

Riva811

Active Member
Joined
Jan 7, 2018
Messages
604
Location
London
Car
CL500 Blueefficiency
Thanks for the thoughts. Not sure how much a laser thermometer will cost, might as well go through a process of elimination. I suspect the thermostat is stuck wide open.

Sent from my J8110 using Tapatalk
 

pillow

Active Member
Joined
Feb 19, 2019
Messages
77
Location
Hampshire
Car
W216 CL600
Well if you're stationary you should see the temperature rise to somewhere near normal. It's only when you're moving that a stuck thermostat becomes apparent.
 

Dichtung

Active Member
Joined
Oct 16, 2007
Messages
300
Location
N.W.
Car
W203 2.2Cdi
Another quick check is to feel at the big bore coolant pipe from top of engine to the radiator. If it is warm within minutes of starting a cold engine, the thermostat is stuck open/faulty.
 

OneForTheRoad

MB Enthusiast
Joined
Apr 20, 2015
Messages
2,724
Location
uk.
Car
2017 e350 c207 .. +65 ford kuga 2.0 cdi zetec awd..
Mb2 will tell you the actual temperature.
 

E55BOF

MB Enthusiast
SUPPORTER
Joined
Mar 11, 2013
Messages
6,815
Location
South Bucks
Car
S211 E500, SLK55, FJR1300, Caponord
Mb2 will tell you the actual temperature.
It will tell you what temperature the sensor is indicating. If the sensor is reading too low, so will the MB2. That said, though, it's more likely the thermostat is failing/has failed than that the sensor is faulty. A faulty thermostat will not generate a fault code; a faulty sensor might.

Dichtung (post #9) is right. The outlet hose to the radiator from the engine should remain cold or cool - there may be a slight leakthrough of heated coolant before the thermostat starts to open - until the thermostat starts to open, then heat up quite rapidly once coolant starts to flow through it. If it warms up steadily as the engine does so from a cold start, then the thermostat is definitely the culprit, not the sensor.
 
OP
OP
Riva811

Riva811

Active Member
Joined
Jan 7, 2018
Messages
604
Location
London
Car
CL500 Blueefficiency
It will tell you what temperature the sensor is indicating. If the sensor is reading too low, so will the MB2. That said, though, it's more likely the thermostat is failing/has failed than that the sensor is faulty. A faulty thermostat will not generate a fault code; a faulty sensor might.

Dichtung (post #9) is right. The outlet hose to the radiator from the engine should remain cold or cool - there may be a slight leakthrough of heated coolant before the thermostat starts to open - until the thermostat starts to open, then heat up quite rapidly once coolant starts to flow through it. If it warms up steadily as the engine does so from a cold start, then the thermostat is definitely the culprit, not the sensor.
I noticed what you described with the gauge, it starts low, goes high and then drops. Don't really want to buy a laser thermometer for an one off hopefully

Sent from my J8110 using Tapatalk
 

E55BOF

MB Enthusiast
SUPPORTER
Joined
Mar 11, 2013
Messages
6,815
Location
South Bucks
Car
S211 E500, SLK55, FJR1300, Caponord
I noticed what you described with the gauge, it starts low, goes high and then drops. Don't really want to buy a laser thermometer for an one off hopefully
That suggests that the temperature sensor is OK, and the thermostat is working OK-ish from cold, but once it's opened as the engine warms up, it's staying open a little wider than it should once the coolant reaches operating temperature. I'd replace it and see what happens.

Google "replacing thermostat on (whatever year your car is) CL500"; you may find it's a very simple process. I had to do it on a 2008 W211 E350 petrol, and it was very easy indeed; not even any jubilee clips to replace - the hoses were all held in place with circlips. If you use an aftermarket 'stat, buy one made by an OE supplier like Febi; steer clear of names you've never heard of, like Cercoli.
 
OP
OP
Riva811

Riva811

Active Member
Joined
Jan 7, 2018
Messages
604
Location
London
Car
CL500 Blueefficiency
That suggests that the temperature sensor is OK, and the thermostat is working OK-ish from cold, but once it's opened as the engine warms up, it's staying open a little wider than it should once the coolant reaches operating temperature. I'd replace it and see what happens.

Google "replacing thermostat on (whatever year your car is) CL500"; you may find it's a very simple process. I had to do it on a 2008 W211 E350 petrol, and it was very easy indeed; not even any jubilee clips to replace - the hoses were all held in place with circlips. If you use an aftermarket 'stat, buy one made by an OE supplier like Febi; steer clear of names you've never heard of, like Cercoli.
This is for a W212 which is very simple, on my CL216 with M278 is a pain in the rear
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom