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230E 1992
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Discussion Starter · #1 ·
i bought my 230E 10 months ago and about 6 months back i noticed that my cooling water expansion tank have some oil(color is light brown). I showed it to my mechanic and he said that my ATF is mixing with the water. So I changed my radiator. Just 3 days ago I found thesame thing. The engine oil is fine as it is very clean and engine temp is just reaching 85 deg C. So we thought that the oil is coming from the ATF again. If my mechanic is right that this oil is from ATF, what is the reason why the radiator is getting damaged or oil is present in the tank?
 

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95 E320 Cabriolet, 140K
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I find it odd the diagnosis was simply the mechanic looking at the expansion tank, making the determination, and there was no further investigation.

Usually the first step in this problem is to flush out the cooling system using a flushant that will clean out the oil (such as Shout, Dawn, or the dealer-supplied flushant), then check to see if the problem returns.

What does the transmission fluid look like? Water in the transmission would result in expensive damage. Was that addressed?

Sometimes the head gasket can leak in a way that leaks oil into the cooling system.
 

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1982 Peugeot 504 Familiale
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1,730 Posts
Can you actually look into the expansion tank and see the oil floating on top of the coolant?
Maybe the brown color you dscribe is just plain old-fashioned rust. Are you using an antifreeze/anti-corrosion agent?

Shady
 

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G320 & E500
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What is the first signs of a blown head gasket!

Chuck
 

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1982 Peugeot 504 Familiale
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1,730 Posts
What is the first signs of a blown head gasket!
Oil floating on surface of coolant.
Water/coolant in engine oil (oil will look like milkshake) and loss of coolant.
White vapor coming out of exhaust on a warm day.

Shady
 

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230E 1992
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Discussion Starter · #6 ·
we actually checked the quality of the transmission oil and it seems that it has no water in it, it looks very clean and there is no change in the way it shift. My mechanic said that there is no way for the oil/water mixture to go back to the transmission as the pressure of the fluid is more than the cooling water. It means that the mixture will just stay in the radiator/expansion tank and to the engine block. He said that if the water is mixing with the engine oil the enigine temp will definitely rise and color of oil in the engine block will also change. Color of the oil in the expansion tank and radiator hoses is light brown. There is no white smoke from the exhaust.

Anyways, we have already replaced the expansion tank and radiator/hoses recently. we will just observe. Thanks for all the response.
Kestas - 2/13/2005 6:24 PM

I find it odd the diagnosis was simply the mechanic looking at the expansion tank, making the determination, and there was no further investigation.

Usually the first step in this problem is to flush out the cooling system using a flushant that will clean out the oil (such as Shout, Dawn, or the dealer-supplied flushant), then check to see if the problem returns.

What does the transmission fluid look like? Water in the transmission would result in expensive damage. Was that addressed?

Sometimes the head gasket can leak in a way that leaks oil into the cooling system.
 

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2007 S65 AMG, 2003 S500, 1997 SL500, 2008 QX56, 70 Buick GS,
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66 Posts
My 88 300E just developed the same problem. It is definitely engine oil in the reservoir and not tranny fluid. I found some tan milkshake like foam clinging to the inside of the cap. I siphoned of several ounces of oil floating on the coolant in the expansion reservoir with a small hand vacuum pump and put it in a jar so I could look at it up close to be sure it was oil. There is zero water in the crank case and the oil looks great since I change it often. Yesterday I drove from Atlanta to Mississippi and back approximately 800 miles round trip and the car ran perfectly. Speed most of the time was 75 to 80 mph but there was some stop and go driving too. Noticed nothing at all different about how the car ran and the engine maintained 85 deg C when warmed up. Ambient temp was around 40F in the morning up to about 75F in the afternoon. I was half expecting the engine to seize up or something during the trip. Everytime I stopped I opened the cap and saw that milkshake in the reservoir.

I am guessing this is a blown head gasket or even worse a cracked block. With either of these however I would expect the engine to use a lot of water, steam coming from the exhaust, or water in the crankcase oil but none of this is currently happening.

Anyone else ever had this happen to them?

Thanks
 

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You have a blown head gaskette. Or more precisely a leaking head gaskette. I guarantee the oil will come back.
The oil in the tank is just the first sign and I ran like that for about a year with no issue. When I decided to fix it I had them do the valve stems and seals while they were in there. I then ran the MB acid sold at the dealer through the system to clean out the residue. No problems since.
 
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