C220 CDi Cold Running

[oigle]

I think the fact that there is an inline thermostat (Photo in previous post) means that the heat exchanger does both the warming up and cooling of the ATF. (Just as the lower part of the Radiator does).
If you think about it when the engine is cold then the thermostat is shut and so the warming coolant flows around the heat exchanger and warms the ATF.
(Remember the ATF is actually fed into this "heat exchanger")..
Once the engine is up to temp then the thermostat opens and allows the heat exchanger to be "cooled" to the correct running temp (I assume around 85C)..

In view of this I would ask a different question to yours...
With a "Heat exchanger" warming up and cooling down the ATF then couldnt we do without the half arsed split radiator design?
In other words couldnt the lower section of the Radiator that carries the ATF be bypassed by removing both ATF hoses and joining them together?
In a climate such as ours would this be such a problem?
As things stand we have 2 radiators that cool/warm the ATF..
I am all for simplicity of design and I cant help thinking that its overdone..
I never tow caravans and rarely thrash my car so I am fairly confident that I for one would be able to get away with such a mod..
Obviously people in hot climates that tow (Hi Mr Oigle) may not get away with this.
My gut instict is that the potentially troublesome lower Radiator could be dispensed with on this engine in this climate...
Just my thoughts..

Hi Simon - I think you could do that but the margin for cooling would be substantially reduced. Perhaps one would need the separate rad out front, hooked to the heat exchanger, if you want to remove the rad from the system - just for those long hill climbs etc.

 

[Roxie]

As shown in the only cooling circuit diagram that shows this radiator configuration, it is for code 921 for use with bio fuel. So I think given that it is a 611 engine that struggles to get hot at the best of times that this radiator is to shorten the heating up times and heat the fuel to prevent waxing.
This cooling system is not used in tropical climates

 

[umblecumbuz]

... I think given that it is a 611 engine that struggles to get hot at the best of times that this radiator is to shorten the heating up times and heat the fuel to prevent waxing.

Wouldn't have thought that heating the fuel to prevent waxing is the reason. Waxing would normally occur during the coldest part of the 24 hour period - ie. during the night, when the car is also at its coldest because of non-use. Once the car is started and the fuel is moving, waxing is less likely.

I have just fitted a new stat to my C270, and the difference is amazing. So I congratulate the wisdom of the experts on this forum when they repeatedly state that the main stat is most likely the cause of low-temperature running. The heater actually gives out real heat, and the engine hits 85 within 4 miles (rad is completely muffed, as it has been for the last two months).

Baz

 

[Roxie]

Okay I generalised to keep it simple. In fact I don't mean Bio fuel I mean Vegetable Oil or Methyl Ester fuel (Code 921) This has to be heated to bring the viscosity down before it is used in a engine designed to burn Diesel. This is so that the injection system does not clog up and ensures proper atomisation of the fuel and therefore a more complete burn. This then reduces the chances of carbon build up in the combustion chamber and makes the engine last a bit longer.

 

[Alex Crow]

Okay I generalised to keep it simple. In fact I don't mean Bio fuel I mean Vegetable Oil or Methyl Ester fuel (Code 921) This has to be heated to bring the viscosity down before it is used in a engine designed to burn Diesel. This is so that the injection system does not clog up and ensures proper atomisation of the fuel and therefore a more complete burn. This then reduces the chances of carbon build up in the combustion chamber and makes the engine last a bit longer.

The extra rad and thermostat on the front of the car are there to cool the fuel, and are fitted to ALL (in the UK at least) CDi2 c220 and c270 cars - ie any vin that fits WD*203*06 or WD*203*16.

 

[Roxie]

The only cooling system diagram that includes this radiator is the one posted, and is for om611 engines only. with code 921.

 

[Alex Crow]

Well my EPC lists it for 612 engines as well, in the cars I listed earlier, a VERY common fitment.
EPC makes no mention of any special codes or versions for it to be applicable to either.

 

[Roxie]

I totally agreee I have one on my C270.

The thing is the OP requested a piping diagram and as I said at the time the only one available that depicted this radiator is for code 921 as it clearly states on the diagram. Now I don't know if the OP's car has code 921 and as I dont know the full chassis no. I have no way of finding out. I then have been tasked with explaining what this radiator does on a bio fuel burner, and have done so.

Before someone else notices I know that this is also all very strange because CDI engines are not approved for use with Bio fuel.

 

[Martin Jennings]

Rather glad I refered back to my Jaguar problem now! Now, does anyone have the definative part number for MB UK for this stat as I am sure mine is stuck open as over the last few days just under 80c is as hot as it will get after 20 miles or so, and yes, I have changed the main stat a few months ago and up till now has been maintaining 90c with no drama. Seems easy enough to do on inspection, just unbolt the horn bracket and 2 hoseclips should release it!

 

[Martin Jennings]

Well, I've just had 1 hours worth of "discussion" with the Parts Department at Robinsons in Norwich and all I've left with is a picture of the cooling system from the computer screen saying that I have to purchase all of the surrounding pipework to the Low Temp Rad to get any parts that are within this section !!!!!!!!!! Told the chap nicely that there was more chance of me buying an Arsenal season ticket than doing that to get an inline stat! He then said "what stat?", took him outside and physically showed him "what stat" and he said "oh!" Went back inside and have been told that according to Mercedes Parts diagrams it does'nt exist and they have no part number for it. I GIVE UP!!!!!!!!!!!!!!!

 

[Alex Crow]

As far as I know, it is only available when buying a new aircon condensor.

 

[Mercedes-2010]

As far as I know, it is only available when buying a new aircon condensor.

I don't doubt this, but, how silly of MB to do this!

 

[television]

I don't doubt this, but, how silly of MB to do this!

This is happening on many items now,,, the 230 has sensors in some of the valve blocks,,you can no longer buy the sensor circa £50,, you buy the complete block at £1k

 

[Martin Jennings]

Thanks for your patience trying to find the part number Alex, Not sure how to approach it now.

 

[Alex Crow]

Thanks for your patience trying to find the part number Alex, Not sure how to approach it now.

No numbers stamped on your thermostat? - I guess you thought of that!

 

[Martin Jennings]

No numbers stamped on your thermostat? - I guess you thought of that!

Actually, no, I did'nt. I was busy seething at an 18 year old telling me the bit did not exsist at the time. I will have a look when I get a chance. :Oops:

 

[mersum1es]

This is happening on many items now,,, the 230 has sensors in some of the valve blocks,,you can no longer buy the sensor circa £50,, you buy the complete block at £1k

Yep, there was a time when you could by a parktronic sensor from the common electronic supplier, it fitted directly to the MB's bumber, even the connector was the same. And price was 20% compared to MB original sensor... sorry offtopic :Oops:

 

[oigle]

Resurrecting a thread a bit here but have had another thought on this.
My ML has been running too cool - around 65°. Gets to that fairly quickly and then sits there until a hill or heavy work. Pulled the thermostat the other day and checked its operation. Worked fine - just too early. Inserted a spacer under the spring to increase tension and reassembed.
Interesting thing is - temp gets to 65 after about 5km then increase stops. Look at gauge again after another 10-15km of normal light load driving in 25° temperatures and it has gotten up to about 75°. The eventual increase is due, I think to the thermo mod.
However, what causes the "stutter" in the temp rise? I'm inclined to think that the thermo in the line to the "low temp rad" may be at fault, opening around the 65° mark. This would cause the coolant temp to hold at that level until the little rad could no longer control the heat being produced and the temp then gradually continues to rise until the main thermo finally opens.
Thoughts anybody?
What I think I might do is wrap the "low temp rad" in heavy plastic to prevent airflow through it for normal driving and take it off when I go caravanning. Considering the fact that many models rely on the heat exchanger without an extra rad for their auto oil temp control, I can't see where it can hurt in normal driving. This won't prevent any coolant circulation but would stop the unwanted extra cooling.
Anyone have any negative thoughts about doing that? Don't want to blow something up!!!

 

[mersum1es]

Some guys in finnish MB forum have just squeezed the hose of the low temp rad with lock pliers. None of them have reported any problems... but why not change the stat of the low temp rad?

 

[Alex Crow]

...... why not change the stat of the low temp rad?

A good idea, but seemingly it is not available as a seperate part, or rather, no one has been able to find a part number for it (including the guys at MB).