C200 W202 Hissing and fluid leak but running fine.

josephcieslik

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My Mercedes C200 W202 has just started making a hissing noise at the drivers side in the engine bay and is also leaking some fluid from the same area which is running down and dripping underneath the drivers door.
Please could anyone tell me what is causing this?
The brake fluid seems to still all be there and the car doesn't seem to have lost any coolant.
The engine is running as normal and driving well, the steering is fine and the brakes seem to be working as normal and are not heavy. The central locking system is also working perfectly.
I thought it may be something to do with the vacuum for the central locking but why would there also be a fluid leak?
I can't understand this as the car seems to be leaking a lot of fluid and hisses constantly when the engine is on, yet the car still seems to be functioning as normal.
Any advice would be greatly appreciated!
Thanks.
 

Xtractorfan

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S class
The fluid leak may just be the normal condensation from the aircon.. the hissing sound could be a turbo /intercooler pipe coming adrift, tho this will normally cause loss of power.. worth finding an indie and letting him have a look..some of the other lads will maybe be able to pinpoint your exact problem..
 

nickcc101

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S203 C180 auto estate 2001 (sold)
Is the leaking fluid water or oil. Doubt if you would hear a vacuum leak. Is there a turbo/supercharger fitted ? Is there a loss of coolant from the header tank ?
 
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josephcieslik

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Hi, I think the liquid is water, certainly not oil.
Coolant all there still.
There is no turbo / supercharger fitted.
I am very puzzled by this one, hoping I'm not going to have to take it to Mercedes!
Cheers.
 

roofless

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w124 e220 estate
if it's not from the coolant or washer fluid bottle ect the only other thing i can think of that produces water & noise is the exhaust ???
 

nickcc101

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S203 C180 auto estate 2001 (sold)
Could be water running on to the hot exhaust causing the hissing. If you have a water leak it may have been the head gasket but you say the coolant level is ok so that rules the gasket out. The only obvious places where you have water is either the coolant system, screenwasher or aircon condensation drainage point (as already mentioned), unable to think of anywhere else. Cheaper option than MB is local Indie.
 
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josephcieslik

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Turns out that the brake servo had somehow got wet and then rotted through - the hissing is a hole in the servo but the liquid remains a mystery unless it was maybe inside the servo.
Trying to get hold of a nice cheap replacement servo now - I've seen one or two used ones for sale online.
Is the servo pretty much standard for the model? The car has ESP / BAS so I was wondering if this would require anything different?
Thanks again.
 
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