what is "normal" operating engine temperature

[C240Sport97]

My CLK 55's (W208) water temperature is usually about 85C. In heavy traffic however, it goes to more than 104C. I know that 104C is still not in the 'danger' zone, but don't understand why in the C240 (W202) I had, it never went above 90C, regardless of how bad the traffic was.

The coolant is at MAX, and was changed Aug 2004. The viscous (i.e. not the electric ones) fan is turning.

Is there anything else I should be checking?

Should I be worrying about this? Or is this 'normal'?

 

[Dieselman]

The electric fans should be coming on slowly at this temperature.

 

[C240Sport97]

at what temperature?

The electric fans should be coming on slowly at this temperature.

 

[silverarrow]

known fault fan control relay £105 and 10 mins

 

[andy_k]

not sure it is a fault and certainly not worth spending £105 on something that doesn't need fixing.

the thermo coupling and thermostat will both kick in at 105C (there's that magic number again)

I think you'll find that's what is classed as "normal". It certainly is for the W123 and W124 series

Andy

 

[Satch]

Watch the temperature over the coming weeks. May not be a problem at all but if it starts creeping up action is needed.

Have a chat with Stealer to find out what specified operating range is. It took me by surprise to learn that engine operating temperatures have been creeping up for a while now, with some new models having a nominal operating temperatures of 110C and are still in the happy zone up to 130C!

Couple that with smaller radiators, introduction of 42v systems (better ability to drive electric ancilliaries but more heat load) and engine cooling is already the subject of a huge research effort.

Lots of cars have auxilliary electric coolant pumps already but in a few years wholly electric driven and ECU controlled cooling systems will be the norm. That will enable faster warmup and enable the engines to better run in the correct temperatutre band to reduce exhaust pollution.

Sadly, will give more things to go wrong in a critical system and no doubt we will soon be harking back with nostalgia to the good old days of mechanical pumps, wax thermostats you could whip out if it all went horribly wrong and simple antifreeze rather than the complex chemical soup required by high temperature engines

 

[C240Sport97]

this is the plan .. since Summer is supposedly here.

thanks for all your feedback.

Watch the temperature over the coming weeks. May not be a problem at all but if it starts creeping up action is needed.

 

[glojo]

If in doubt I would definitely check with the dealership.

If the temperature is okay then fine, but do not leave it until summer. Being stuck in a traffic jam with the temperature going off the clock is not a situation anyone wants to be in.

Hopefuuly all is okay, but it makes you think about water pressures and what would happen if a hose split??

Good luck,
John

 

[GregE240]

I'd go with Johns advice.

Get it looked at. For the sake of, I dunno, £50 at the dealers, what if they find a sticky thermostat? What if the fan control relay is on its way out?

A small price to pay for peace of mind, IMO.

For the record, my E240 usually hovers around 85 with aircon off, slightly more with it on. In traffic it does go up a little, but I know both the aux fans work okay.

Just my two cents worth.

Greg

 

[nickmann]

I see 80-85 on my 240 in normal use. With 4 passengers, 5 bikes on the roof and the boot crammed full on a hot day on a steep hill I have seen 100 degrees. Also 100 stuck in traffic. My viscous fan passes the carrot test, and the lekky fans work fine.

I changed the thermostat and the top hoses, and reverse flushed the system (which appeared squeaky clean). It made not one iota of difference. So either the rad needs replacing or the system is working within tolerances. I accept that at 7 years old it is conceivable that the rad needs replacing.