W220 S500 coolant leak.
 

Hi everybody,
When driving my car today the low coolant warning message appeared, so I went to check under the bonnet and the level was a bit low. I could also hear a few drops of water dripping and sizzling on the exhaust instantly turning it to steam, this is at the back of the engine on the passenger side just in front of the firewall.
The car is driving fine and the temp gauge is sitting exactly where it should be. I just wondered what cooling components are at the back of the engine that could drip down like this.
I'm supposed to be driving to Sheffield and back tomorrow which is 100 miles round trip!!! I'll take some spare coolant with me and hope it doesn't get any worse!!'
Cheers guys.

There is a heater neck in that area prone to failure

Probably the plastic bulkhead fitting in the heater hose - a common failure point.

https://w220.ee/WIS_20.20_Radiator,_Coolant_Hoses

I did a write-up some time back - hope that it helps!

http://www.benzworld.org/forums/w220...lant-pipe.html

Hi,
***UPDATE***
Thanks for the help!!! You are absolutely right, I found that plastic pipe on the bulkhead and that is where it's dripping from.
It happened on my way home from work, there is quite a steep hill so I gave the car a bit of welly getting up it and it was when I stopped at traffic lights at the top that I spotted a small amount of steam coming from the passenger side near the bulk head and the coolant level warning message appeared, the temp gauge stayed where it should, the coolant level was about 3/4 of an inch below where the black lid starts so I topped it up when I got home, the expansion tank cap didn't hiss to relieve pressure like I expected, would this be due to lack of pressure where the leak is?

As a further test I decided to put the climate control to HI and only cold air came from the vents and the amount of coolant leaking and steam increased, when I turned the climate back down it seemed to reduce again. I don't mind managing without a heater for a day or 2 until I can try fixing it.

My question is, if I carry some spare coolant just in case, will the car be safe to drive with the heater turned off because I'm supposed to be going to Sheffield tomorrow which is about 100 miles there and back again!!!

Thanks again for your help and input!!!

Not safe to drive
rent a car

You could use a bottle of K Seal which will work for the trip but you do need to change the part as soon as possible.

Another quick update. I ended up borrowing my sisters car for the Sheffield trip as I didn't want to risk it.
I took the car to my local mechanic and he put some stuff in the coolant which is supposed to fix leaks (probably k seal or similar) and so far it doesn't seem to be working!!! Does it take many miles for it to take effect? I've done about 30(steady)miles since the stuff was put in.
Another thing I've noticed now the weather is turning colder is that at low engine revs my heater only blows cold air, would this be caused by this plastic pipe leaking? If you rev the engine it starts to get warm but the steam also increases from where the leak is. The engine temp gauge sits at about 80 degrees which seems normal I think.
I've found a place online that sells this part for £6.75, I'd like to have a go at fitting it myself but realistically how easy is it to do as a DIY job? I'm not that mechanically minded but have tackled very basic jobs on cars before now!!!
Thanks again guys for your help!!!

Cooling system sealer plugs up heater cores and should never be used ! Get your mechanic to change the part

I'm not an expert yet on benzes, but I came across this video and maybe you may want to check something called the duo valve?
I believe this may be an electric valve to let in warm coolant to the heater cores to open up and pump heat into the cabin.

Other than that I would be inclined to say an old thermostat.