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Mercedes C180 K 2006 W203 271
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Discussion Starter #1
Hi all my cars coolant tank keeps overflowing , car does not over heat and drives smoothly. But when I stop and it idles for n few minutes the tank over flows . when you open the hood you hear how it sucks water. There is also a black liquid in the tank. Can it be head gasket that has blown. 2006 C180 K 271 W203 please assist
 

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There is also a black liquid in the tank.
About the only thing black that could get into the coolant is oil, which would indicate it's mixing somewhere. It would have to be a crazy serious leak to make your coolant overflow though! You are using a 50/50 mix of coolant, and not straight water...correct?

Do you have coolant in the oil as well? You would see it on the dipstick (if you have one) or a peanut butter like goo on the underside of the oil fill cap? It doesn't have to be the head gasket, it could be the radiator or oil cooler. But if you have fluids mixing you have to fix it ASAP or risk ruining your engine.
 

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Mercedes C180 K 2006 W203 271
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Discussion Starter #3
About the only thing black that could get into the coolant is oil, which would indicate it's mixing somewhere. It would have to be a crazy serious leak to make your coolant overflow though! You are using a 50/50 mix of coolant, and not straight water...correct?

Do you have coolant in the oil as well? You would see it on the dipstick (if you have one) or a peanut butter like goo on the underside of the oil fill cap? It doesn't have to be the head gasket, it could be the radiator or oil cooler. But if you have fluids mixing you have to fix it ASAP or risk ruining your engine.
No I have check the dipstick is fine I drive it at 220km this morning and it drove smoothly, when I stopped at work it overflows
 

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How do you know it overflows? You are finding coolant on the ground? Are you sure it's coolant and not condensate from the A/C?

There isn't any way for your car to magically make more coolant, so it is either being displaced by another fluid or boiling over. You are using a 50/50 mix of coolant, and not straight water...correct? If so, you could simply have a bad reservoir cap not holding pressure.

The black fluid in the coolant is a separate issue that you should have investigated. If it truly is oil, you have fluids mixing and that should be fixed fast.
 

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Mercedes C180 K 2006 W203 271
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Discussion Starter #5
No I have check the dipstick is fine I drive it at 220km this morning and it drove smoothly, when I stopped at work it overflows
50/50 coolent , when I press on the brake when I stop I can feel a little bit of an vibration on the engine. When it idles in park it idles normal, but when in drive the idling smoothness changes.
 

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Do you have an automatic transmission? Check your trans fluid if you do.

The engine vibration might not be related. Sounds like motor/transmission mounts going bad.
 

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I think your water pump may be on it鈥檚 way to failure. You stop and the coolant then boils, out....

Black fluid all throughout, or there are two layers and one part is black? I was told by a shop the oil goes to coolant, in my case it was transmission fluid, (in the W201).
 

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Black in the coolant is not a good sign . Would say as above,, oil from the engine,, or the auto box is mixing with your coolant.Some auto boxes have the cooler pipes going through the coolant radiator . If these are corroded inside the rad the ATF oil will get in to the coolant and this might be what you are seeing .
 

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Discussion Starter #9
Thanks Guys the black liquid is not that much maybe I a teaspoon in the coolant tank
I will check out all you have said and repair
 

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I would also replace your coolant cap. It shouldn't be letting anything overflow unless it is crazy hot or overfilled, which you say it isn't.
 

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Any black liquid on the coolant tells me you may have cylinder head problems .Or auto box arf fluid is leaking in to your coolant .I hope its not try and lift some fluid out to take a better look at it ./
 

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Mercedes C180 K 2006 W203 271
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Discussion Starter #12
Any black liquid on the coolant tells me you may have cylinder head problems .Or auto box arf fluid is leaking in to your coolant .I hope its not try and lift some fluid out to take a better look at it ./
Thanks I did it is not like icream no smoke and it drives smoothly I drove it at 240 km no issues but when I stop the violent tank overflows and idling is out
 

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Thanks I did it is not like icream no smoke and it drives smoothly I drove it at 240 km no issues but when I stop the violent tank overflows and idling is out
Once again, start by replacing the coolant cap. It's cheap. If you aren't overheating (temps in normal range), there is no reason for things to violently overflow unless the cap is shot and not holding pressure.
 
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