Help! W204 coolant leak

[rogeroaune]

I hope I'm posting in the right thread, if not I'm sorry and please redirect me to the correct one (I'm new here). I have a 2011 c class 200cdi. Engine OM651. It seems to be coming from the mid upper right side of the engine (Picture attached). And it's a big one, but I can't pinpoint the location. When cold and in idle, there is no sign of any leak. But once I start driving it starts leaking alot. Been using the car as I need it to get to work. And constantly have to refill just to give it some cooling. The engine has gotten really hot at some point too. When that happened, steam was coming out from said side of the engine. There's no smokey exhaust from what I can see, and the oil looks good aswell. I've taken a look at the fuel filter housing and I don't think it's from there. I am no mechanic but I enjoy fixing my car by myself. But now I have given up trying to find this leak by myself. Do anyone of u have any idea what it could be? Thank you

 

[w204benz]

Almost certainly the fuel filter housing, especially if it is the original.

I had the same symptoms - everything normal for a few miles, then once the engine reaches operating temperature (probably when the thermostat opens) there was a massive leak in the same location and a 'coolant low' warning.
A few bottles of DI water would then give me a few more miles before it happened again. I managed to avoid overheating the engine, but I still saw steam after the bulk of the water leaked out. Unless the temperature gauge was at maximum, you may be lucky and it didn't get hot enough to cause any damage.

When the mechanic showed me the failed housing, the seal had collapsed on the inside. So I'm not surprised you couldn't see anything wrong just by looking at it. I'm just guessing it is the housing by the location of the leak and the fact that you're describing the same situation I was in some time ago - you probably won't see the failure until you take it apart.

 

[alexanderfoti]

If its not the fuel filter housing (wihch is closer to the center of the head), then its likely to be a cracked housing at the rear that connects to the EGR Heat exchanger.

This normally happens when bolts are left of out the brackets when somebody has had it off in the past.

 

[Craig71]

Almosen certainly fiel filter housing. The seal inside goes and causes a huge leak as you describe. Very common, mine went too. Part is very cheap, about €30 here in germany but it's a pig of a job to do and will cost a fair bit in labour at a garage.