C32 AMG, C55 AMG (W203) 2001 - 2007

Need urgent help please - Oil in Coolant Reservoir 2003 C32 AMG Eurocharged Stage 3

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Old Jan 5, 2018 | 12:52 PM
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Need urgent help please - Oil in Coolant Reservoir 2003 C32 AMG Eurocharged Stage 3

I was loosing coolant every few days so I brought my car to a good indy and asked to check if the leak is coming from the intercooler. They got back to me saying yes it was the intercooler, I looked in my area and found an intercooler in good condition which I got shipped to them and had it replaced. To my surprise, the intercooler that I have ordered is what I know as the heat exchanger 110/11 which mine was a Eurocharged one. They replaced the eurocharged heat exchanger with the OEM one I ordered and it helped a bit but now I'm still getting low coolant level but it took longer to get the sign on the dashboard. I brought back the car and they told me they found a bit of oil in the coolant reservoir. I'm suspecting the Oil Cooler as I thought originally (110/2) which is a known issue. Now they throw away my Eurocharged intercooler (110/11) and I have stage 3 mods on the car, what is the risk of running an OEM heat exchanger?


Last edited by Elideli; Jan 5, 2018 at 01:10 PM.
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Old Jan 5, 2018 | 05:02 PM
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Ok I just came back from the shop and they removed the oil cooler and did tests and confirmed that Its not leaking. He thought about head gaskets but he couldn’t believe as he told me that it would be extremely exceptional to have issues with head gaskets in this engine. He removed the oil excess from the coolant reservoir and compared it to the engine oil, and the oil was much much lighter than then engine oil. He is now suspecting the transmission oil which could be due to an issue with the radiator. This car is a 2003 one which had the Valeo radiator issue fixed.

When returning to home, I opened the hood and suddenly I saw a little of fume coming out from where the coolant reservoir is located. And it smelled the exact same odour as I have smelled many times in the cabin when the car was on idle. It was coolant that was evaporating. I went straight to see and saw indeed some coolant sitting under the reservoir. I have attached video for you to see. Could all this headache be due to a cracked hose coming from the coolant reservoir? I’m having this issue since six months, never lost power, never had misfire, I only lose coolant all the time. I’m sure it’s nothing major but I need to get this fixed once and for all.

edit: I could not attach the video but I have uploaded it to Dropbox: https://www.dropbox.com/s/k9akpo36us...%20PM.mov?dl=0

Last edited by Elideli; Jan 5, 2018 at 05:16 PM.
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Old Jan 5, 2018 | 07:58 PM
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So is the coolant leaking from the reservoir? Looks like there's some around the top of the reservoir like it had overheated?

So you checked the intake plenums? is there coolant caked up there? The common place for coolant leaks is the intercooler aka "Charge Air Cooler 110/2", NOT the heat exchanger. That is what most people end up replacing.
If you do end up replacing it, do not get an OEM one, get the aftermarket one from Speedriven. Unfortunately, I see that their website is no longer up but I see they have a FB page. I also see they are listed as "Banned" from MB World.

I replaced my leaking intercooler with a New OEM one and it leaked agin in over a year. I have the aftermarket one and no issues for 4+ years.

OEM heat exchanger with your mods is going to take longer to recover from heatsoak, so you will have loss of power once hard on the throttle.
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Old Jan 5, 2018 | 09:08 PM
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Originally Posted by Gramma_Benz
So is the coolant leaking from the reservoir? Looks like there's some around the top of the reservoir like it had overheated?

So you checked the intake plenums? is there coolant caked up there? The common place for coolant leaks is the intercooler aka "Charge Air Cooler 110/2", NOT the heat exchanger. That is what most people end up replacing.
If you do end up replacing it, do not get an OEM one, get the aftermarket one from Speedriven. Unfortunately, I see that their website is no longer up but I see they have a FB page. I also see they are listed as "Banned" from MB World.

I replaced my leaking intercooler with a New OEM one and it leaked agin in over a year. I have the aftermarket one and no issues for 4+ years.

OEM heat exchanger with your mods is going to take longer to recover from heatsoak, so you will have loss of power once hard on the throttle.
My mechanic said that he took out the intercooler and made pressure tests and they were negative. Now the question is: can the intercooler leak even though tests are negative?

The coolant you see on top was from before when I opened the reservoir while it was a bit hot. The car never overheated. It can’t be a blown headgasket, there is no white smoke, the oil cap has no milky substance, and the car never misfired. I always make sure the engine temperature is what I see on my dashboard while I drive the car and it always run at 90 degrees with normal driving and never went up 100 degrees when driven hard. All this knowing that its been almost a year and 7K miles since this mysterious coolant loss appeared. I would assume that if it was a head gasket, things would have gotten worse since then.

I have just placed some white paper under the car where the coolant reservoir is located, I’ll see tomorrow if there any drop/puddle.

Other issue could be simply coming from the radiator which would be tested on Monday.

Last edited by Elideli; Jan 5, 2018 at 11:13 PM.
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Old Jan 6, 2018 | 08:44 AM
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You need to check the transmission fluid for glycol contamination. If any is glycol is found, replace the radiator with a Behr model. Valeo is known to fail at the trans cooler, and will take out the trans with it. I replaced mine BEFORE it failed.

Get your mechanic to pull an intake plenum on one side and look for coolant ‘slime’ inside. If any is found, replace the charge air cooler as described above with any model except OEM. I replaced mine after finding the slime and have had smooth sailing since then.

Keep us posted on the outcome.
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Old Jan 6, 2018 | 06:03 PM
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Originally Posted by kbob999
You need to check the transmission fluid for glycol contamination. If any is glycol is found, replace the radiator with a Behr model. Valeo is known to fail at the trans cooler, and will take out the trans with it. I replaced mine BEFORE it failed.

Get your mechanic to pull an intake plenum on one side and look for coolant ‘slime’ inside. If any is found, replace the charge air cooler as described above with any model except OEM. I replaced mine after finding the slime and have had smooth sailing since then.

Keep us posted on the outcome.
Holy crap! I furthered my investigations on the Valeo radiator issue and found out that I have indeed a Valeo radiator! I peviously ruled out this possibility as my car is a 2003 but apparently the issue affects cars up to September 2003 and mine is actually a late 2002. I thought maybe the previous owner replaced the Valeo radiator but upon checking with the help of this thread, it was clear that my radiator is a Valeo! They have those little squared/rectangular crimps crimps (see picture below).



Those little squared/rectangular crimps are an indication that you have a Valeo radiator. You can see them on the top right of your rad from the drivers side.

Now the question is what are thare symptoms of a failed transmission coming from a failed Valeo rad? I have to drive back Monday to the shop and it’s about 5km, is there any risk? Is there a procedure to explain how to conduct a glycol test? Or can I just go ahead and replace the transmission fluid completely?

Last edited by Elideli; Jan 6, 2018 at 06:05 PM.
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Old Jan 6, 2018 | 07:13 PM
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If there is glycol in the trans, another 5km probably won’t kill it, but you need to determine if you have glycol in the trans ASAP.
Call any transmission shop or your mechanic and ask him how to test for glycol. If any is found, swap the radiator, and trans fluid and filter.

edit -looks like a simple test strip for glycol: http://www.acustrip.com/cgi-bin/prod...gi?s=ACU711254

Changing the fluid will help, but it will be contaminated again in minutes. Good luck.

Last edited by kbob999; Jan 6, 2018 at 07:16 PM. Reason: added test link
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Old Jan 6, 2018 | 07:46 PM
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Originally Posted by kbob999
If there is glycol in the trans, another 5km probably won’t kill it, but you need to determine if you have glycol in the trans ASAP.
Call any transmission shop or your mechanic and ask him how to test for glycol. If any is found, swap the radiator, and trans fluid and filter.

edit -looks like a simple test strip for glycol: http://www.acustrip.com/cgi-bin/prod...gi?s=ACU711254

Changing the fluid will help, but it will be contaminated again in minutes. Good luck.
Thanks a lot, very helpful! I will report back as soon as I have more info.
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Old Jan 8, 2018 | 05:53 PM
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Confirmed, the radiator I have is a Valeo one and it contaminated my transmission. I have never experienced any rough shift though. So I'm going to do a complete ATF flush. I'm seeing over the web some 722.6 transmission flush kits but I don't know what I need exactly for my case. Any recommendations please?
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Old Jan 9, 2018 | 11:12 PM
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The difficult part is getting the fluid from the torque converter. Search for means of doing that on the forums. That should give you a clue of what you need.
The 722.6 trans is very popular for MB and flushing the torque converter requires unhooking a fluid line if I recall.
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Old Jan 18, 2018 | 11:11 PM
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Ok just to report back as this might be useful for future reference, especially for people living in Canada. I purchased a new Behr radiator from rockauto.com for only 228 CAD including shipping, taxes and duties to Canada. This is the lowest price you can ever find. If you buy the Radiator from Mercedes Canada, they will rape you at 500 CAD + taxes. I bought a case of 12 liters of Shell ATF 134 from a Shell distributor at 70 CAD. This is the same **** that Mercedes sells for 360 CAD. The only thing I bought from Mercedes is pan gasket, filter, drain plug, lock pin and pilot bushing for 70 CAD. I then went to see my mechanic and asked a complete flush of the cooling system and transmission. He suggested to do this in two parts, so I’ll be back in a month for another transmission fluid service. The Behr part number for the radiator is 376 714 331.

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