w204 intermittently losing coolant

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DonVitto

Member
Joined
Oct 4, 2015
Messages
46
Car
Mercedes C180 CGI Sport
I have a W204 2011. Earlier this year I had the "top up coolant" warning come up on the dash. It's the first time since I owned the car I've ever had to top anything up. It had lost about 1 litre of coolant.

I kept my eye on it for around 4 weeks and it didn't lose anything. Then I had a service and they did a presure test, which didn't reveal any leaks. They said they nickname the diesel version "the sieve" because it can leak from so many places, but they said it's more unusual for the petrol version to lose coolant.

Anyway, fast forward some 5 months later, and the same thing has happened again. All of a sudden, the "top up coolant" warning appears, and I've lost around 1 litre again.

Any thoughts or anything I can look out for? I think I'll have to switch checking daily / weekly to find out if it's gradually going down, or losing it all in one go.
 
I have a W204 2011. Earlier this year I had the "top up coolant" warning come up on the dash. It's the first time since I owned the car I've ever had to top anything up. It had lost about 1 litre of coolant.

I kept my eye on it for around 4 weeks and it didn't lose anything. Then I had a service and they did a presure test, which didn't reveal any leaks. They said they nickname the diesel version "the sieve" because it can leak from so many places, but they said it's more unusual for the petrol version to lose coolant.

Anyway, fast forward some 5 months later, and the same thing has happened again. All of a sudden, the "top up coolant" warning appears, and I've lost around 1 litre again.

Any thoughts or anything I can look out for? I think I'll have to switch checking daily / weekly to find out if it's gradually going down, or losing it all in one go.
There are quet a few places that leaks can happen, fuel filter housing, water pump, the hose that goes in the the bulkhead behind the engine, egr cooler. Where are you based?
 
There are quet a few places that leaks can happen, fuel filter housing, water pump, the hose that goes in the the bulkhead behind the engine, egr cooler. Where are you based?

Would these places typically show up in a pressure test? Or perhaps not? I'm based in Leicestershire.
 
Not surprising with two of them being redesigned components .
 
Hang on a minute , what exact engine ?
Ohh you got petrol don't you? Sorry I misread the first post... water pumps are still common and top hose for the radiator too. Alo check your reservoir cap closes with a slight click
 
Much more likely to be going down slowly. You only notice it has lost 1 litre because that is when the light is triggered. On an engine that does not have weak points in its cooling system then the prime suspect for your symptoms would be the water pump failing. It can be quite difficult to spot because it can be a slight drip which evaporates when the engine is hot. It should show up on a pressure test though. Get a decent inspection light and look for tell tale discolouration marks caused by the antifreeze staining where it has leaked. Start around the water pump.
If you live in a hard water area it is better to top up with distilled water rather than tap water. Keep a note of how much water you have added but no point adding antifreeze because the system is probably going to end up being drained at some point.
 
Thanks for your replies. The engine is the 1.8 litre petrol. Not the Kompressor - the later engine I think. I checked today and no coolant lost, but I did notice what I think might be coolant splashes. See photos attached. What do you think? Cheers
 

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Thanks for your replies. The engine is the 1.8 litre petrol. Not the Kompressor - the later engine I think. I checked today and no coolant lost, but I did notice what I think might be coolant splashes. See photos attached. What do you think? Cheers
Yeah there are coolant droplets on headshield over exhaust manifolds, take engine cover off and have a look at the source
 
Check the following

1. Water pump
2. Fuel filter housing
3. Check large hoses going into the radiator. You need to squeeze on each end. If kaputt they will leak.
4. Check for pin holes when car is running.
 
Thanks all, I don't know where some of those things are, but I will take the cover off tomorrow and investigate further!
 

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