W124 Popped a sudden water leak, but engine wasn't overheating!

[sampharo]

Hi guys,

I own a 1994 W124, it's a E280 with an M104 engine. I am new to Mercedes so I am kind of clueless as to how serious this situation is:

Today after coming back from a short drive (10 minutes going, 20 minutes parked, 10 minutes back), and as I was entering the parking, steam started appearing from the front grill. When I stopped and got out to look it was actually spouting both coolant and steam from some valve. Here is the picture of where the coolant and steam came from:





What exactly is it? A pressure valve / backup spout / link ....?

The funny thing is, the engine was at totally normal temperature. at 90 degrees or a hair above. Car has been running on that for months, and I usually look at the gauge and can say that it goes up and down as expected, taking a half a minute or so to edge above 40 degrees when you first start the car and resting between 85 and 95 throughout most drives.

Anyone has any idea what should be plugged in this valve/hole? Is this common? More importantly should I just go and get a replacement "cover" and put it in, marking it off to simply as a failed cover, or was this pressure abnormal and there is a problem with the cooling system I don't know about?

Sam