C220 w204 Coolant leak < Newbie help.

[Arj2292]

Hi Guys, First time posting on here.

So over the last few days my coolant level has diminished to the point of my coolant warning message coming up. The car was serviced last Saturday so it was topped up then.

However today whilst in traffic i spotted a small mist coming from the bonnet seem. I pulled over to take a look. i could hear a hissing noise coming from below the engine cover. The noise stopped when removing the coolant filler cap- i assume relieving the pressure somewhere . I took the cover off and have seemed to locate roughly where the noise is coming from. See the picture below.

can someone give me an idea as to whats wrong here ? or if this is a common thing ?

Thanks for your help guys.

 

[Jimmas]

What you have circled is the fuel filter, so not likely to be that ,but there is a heater hose next to it possibly that, I would re fill with coolant and run the vehicle till it starts hissing again and try and find the mist/ steam before you release the pressure.

 

[Arj2292]

What you have circled is the fuel filter, so not likely to be that ,but there is a heater hose next to it possibly that, I would re fill with coolant and run the vehicle till it starts hissing again and try and find the mist/ steam before you release the pressure.

thanks for your message jimmy, Just spoke to a friend who had the same car. He seems to think there is a matrix or rad of some sort under the fuel filter that was leaking coolant on his. More specifically a bad O-ring. He said this was replaced twice under warranty. Does anyone know what this unit would be ? Currently stranded at work with a broken car.

 

[Oldlae]

It is a heated fuel filter, and you have a leak between the cylinder head and the cheap plastic filter housing. There is a lot to strip down to get access.
A couple of hundred £ job at your local independent workshop.
Tony

 

[TemboKadoko]

Hi there, I've just signed on, to look for help with this very same problem!!! Mines not just losing a little but a lot, around a litre a mile. When i waggel the largest pipe in circled area it changes the pitch of the hissing. W204 OM651 DE22LA125 120k miles 2011.

 

[Retaxus]

You need a new fuel filter housing , the housing has a coolant pipe built in , the flange of which bolts to the cylinder head. The original housing has two studs which attach it, if you buy a new housing from Mercedes it will have 3 studs , the head should already have the correct 3 holes. The problem is that the inlet manifold is plastic and the old type housing is bolted to it. Under high boost pressure the manifold flexes and this causes the leak.
Its a spanner job , took me around 2 hours. Housing from Mercedes was about £30.

 

[TemboKadoko]

You need a new fuel filter housing , the housing has a coolant pipe built in , the flange of which bolts to the cylinder head. The original housing has two studs which attach it, if you buy a new housing from Mercedes it will have 3 studs , the head should already have the correct 3 holes. The problem is that the inlet manifold is plastic and the old type housing is bolted to it. Under high boost pressure the manifold flexes and this causes the leak.
Its a spanner job , took me around 2 hours. Housing from Mercedes was about £30.

Thanks for info, on the 19th I put into the Mercedes Garage at Crawley – I’d run out of time and wasn’t confident about fixing it myself.

The main problem was the Fuel Filter housing with an additional leak from thermostat. It ended up an eye watering £855. I wish i was saying it 2hrs work £30!

 

[Smart320]

Ouch!