2012 c220 cdi coolant issue

Page may contain affiliate links. Please see terms for details.


New Member
May 26, 2023
c220 cdi w204
hi everyone i have a 2012 c220 cdi is on around 151k miles.

a few weeks back i had parked up with engine running and for some reason my car decided to spit the coolant out via the expansion tank cap didnt over heat or come up any warning lights it just happend topped it back up once cooled a little checked for leaks any any obvious reasons for this and everything was fine. then around 2 weeks after, the top up coolant warning appeared checked it out and it seemed to have used little so topped it back up and was fine again up to today when the warning appeared again and had seemed to use quite abit more then last time.

any help or advice would be greatly appreciated TIA.
You have a slight leak somewhere. It can be difficult to find because when the engine is hot the leaking water evaporates. Sometimes you will see staining where the antifreeze has dried - get a torch and have a good look around the water pump and the thermostat / hoses etc. If not then take it somewhere to get it pressurised - the site of the leak should then be obvious. Don't leave it - it will only get worse and it is not good to let an engine overheat. It needs fixing.
Hopefully not a core/freeze plug. Nightmare changing them. Especially the one furthest back on the exhaust side. I had to use red dye poured into my coolant to find out exactly where it was coming from.

Use red dye pour in and best to be under it with all your under panel plastics at front removed and as it heats up and the water flows thru whole system it will become clear where the leak is coming from.
Check the concentration of anti-freeze in your coolant.
The coolant should be a 50% solution of glycol-based anti-freeze.
This significantly increases the boiling point.
If the concentration is less, then the boiling point will be reduced accordingly and the coolant will boil and the system will "spit it out".
If you are topping it up with water, this will be part of the problem.
Also - Check that your pressure cap on the expansion bottle is good.
Again - The system is pressurised and this increases the boiling point.
The pressure cap and the 50% anti-freeze solution should both be good to prevent coolant boiling.
You can check the coolant mix with a hydrometer.

You may not have a leak at all.

Users who are viewing this thread

Top Bottom