C220 CDi Cold Running

[Roxie]

Is this a 611 engine? I am trying to find a cooling circuit diagram that might help. Although you have probably found the problem.

I think with the clamp in the position that you discribe you will be starving the oil cooler of coolant and need to be awair of this and make sure the oil does not get too hot. The pistons are cooled by oil.

 

[teacup]

Yes it's a 611, and that's an interesting point about the oil cooler. I just don't know where the water circuit goes, so while the weather isn't too cold I think I'll play it safe and remove the clamp, or perhap just move it close to where the 2nd stat is, in front of the main rad. In the meantime I'll see if one can pick a replacement stat up from the local dealership.

I read in another post that the fuel cooler was installed in hot climates (UK??) on vehices with plastic fuel tanks, to cure problems starting a hot engine due to a vapour block. Presumably the plastic tank insulates more than a steel one?

 

[Rory]

The little rad on the front is standard equipment on the earlier 220 cdi and 270 cdi W203 cars here in the UK - not sure about elsewhere.
It is known as something like the 'low temperature radiator', and is used for gearbox oil and/or fuel cooling.
If it is stuck it stands to reason that engine temps could run cool, even with a new main system thermostat.

My car has the little rad and discussions about it before have said it circulates coolant to the fuel cooler. The gearbox oil cooler is integrated into the main radiator, isn't it?

Presumeably MB think it's neccesary to cool the returning fuel, so not sure the OP should isolate it by clamping its feed!

 

[Roxie]

The 611 engine is very difficult to get hot when it's cold outside, and many different ideas were used to get it hot especially at slow speed. The only coolant circuit diagram that I can find for you with this additional radiator on is attached. As you will see this radiator is factory fitted to vehicles with code 921 ( fame or bio fuel )

 

[Alex Crow]

............... The gearbox oil cooler is integrated into the main radiator, isn't it?

Not on the CDI2 W203 diesels, ie cars with a 203*06 or 203*16 vin number, these have a gearbox oil heat exchanger mounted on the engine block.
Later CDI3 cars (eg 203*007 or 203*008) have the rad fitted heat exchanger.

And no, clamping the pipe is not a good idea!

 

[teacup]

Roxie, thanks for the images, that explains a lot, although it's impossible to read the 2nd image with the key. Any chance or uploading again at a higher res?

Two things come out of this.
1) The hose clamp between 14 & 4 is safe because it only interrupts flow in the fuel cooler rad 18. The engine oil cooler runs in parallel and won't be affected.

2) What temperature does the 2nd stat(18/3) operate at? I suspect it is more susceptable to ambient temp than coolant temp, considering it's location. I'll ask my friendly dealership if they know.

 

[teacup]

so is the cooler mounted on the the block under the stat and oil filter, for ATF, engine oil or both?

 

[oigle]

so is the cooler mounted on the the block under the stat and oil filter, for ATF, engine oil or both?

ATF only, as far as I am aware.

 

[Roxie]

I don't know how/why that happened try this one.

 

[S.Speed]

I know a 270 isnt a 220 but I notice mine doesnt have the small thermostat for the auxilliary radiator (at least its not where its shown on the photo)..

I seem to recall when I first joined this forum with my other 270, that I asked what that small radiator was for..I remember there were many people whose cars didnt even have that radiator fitted!!
Makes you wonder just how needed it actually is in our climate.

 

[Alex Crow]

Hi Simon, have you followed the pipes from the samll rad? The thermostat is usually behind the horns.

 

[mikedjay]

Cool Runnings

Read this with interest as my E320 seems to have a similar trait, 140 mile round trip, never got above 60 degrees.
I wonder if it could be the same?
Regards
Mike

 

[Alex Crow]

Read this with interest as my E320 seems to have a similar trait, 140 mile round trip, never got above 60 degrees.
I wonder if it could be the same?
Regards
Mike

If it has not been changed, your main thermostat will still be the most likely cause - I do not believe your car has this extra 'stat.

 

[teacup]

Roxie, thanks for uploading the 2nd image again. I just wanted to read the last few remaining items that weren't included on the 1st image. Interestingly, this suggests that the oil cooler (No. 6) mounted on the side of the block is for both engine oil and ATF.

 

[S.Speed]

Hi Simon, have you followed the pipes from the small rad? The thermostat is usually behind the horns.

I shall double, double check tomorrow Alex..
Will photo close up behind the horns if I remember to gat my camera..

 

[Mercedes-2010]

Roxie, thanks for uploading the 2nd image again. I just wanted to read the last few remaining items that weren't included on the 1st image. Interestingly, this suggests that the oil cooler (No. 6) mounted on the side of the block is for both engine oil and ATF.

I'm under the impression that it's the engine oil that aborbs the heat from the ATF via this exchanger, also aiding and maintaing the correct operating temp for the autobox....

Any thoughts? Anyone?

DC

 

[S.Speed]

Hi Simon, have you followed the pipes from the samll rad? The thermostat is usually behind the horns.

Alex,
You are 100% correct.. I actually remembered to have a look this morning for the thermostat you mentioned and there is indeed one just behind the horns..

 

[S.Speed]

I'm under the impression that it's the engine oil that aborbs the heat from the ATF via this exchanger, also aiding and maintaing the correct operating temp for the autobox....

Any thoughts? Anyone?

DC

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..

 

[television]

The only snag that I can see is that when the thermostat is closed no circulation at all is taking place, so the rad stays stone cold till the thermostat opens.

 

[oigle]

The only snag that I can see is that when the thermostat is closed no circulation at all is taking place, so the rad stays stone cold till the thermostat opens.

I do agree. The heat exchanger operates on water within the engine block, not the water in the radiator - I imagine there is a bypass within the exchanger to circulate the block water through it. This means oil temps in the ATF will be lifted to acceptable in a much shorter period. This is probably the reason for the extra thermostat. Once all the water is up to operating temp, the thermos in the head and line to rad both open and a more efficient heat exchanger comes into operation. I guess this also applies to systems where there is an extra rad out front for cooling of the water that circulates through the heat exchanger on the block - like the ML. Necessary for heavy duty use and in hotter climates. I am just guessing here really - just seems to make sense.