losing water

[Graeme 1978]

Hi all bit of a dilemma if anyone can help.

This is a w212 2012 plate 651 engine E-class 2.1 auto

A couple of weeks ago water started bubbling out of the expansion tank so a got in touch with an MB specialist he said it sounds like my water pump was starting to fail so a purchased a new one from MB then a day or 2 later found that the driver side radiator hose was leaking so a purchased 1 of them as well but am still losing water every day am losing up to 1/2 a litre and there's no visible leaks and i have done a pressure test and the pressure dose drop when left but i can not find a leak the only thing that a can find is wetness around all 4 injectors and its not diesel there's no smell so am at a loss now dont no what to do as i'm still losing water it has stopped bubbling out the temperature is fine on the dash board.
Any help please or advice.
Thanks graeme.

 

[SL63 Mark]

Did you fit the coolant pump ? Maybe head gasket ? Did you check the engine oil for coolant ?

 

[Graeme 1978]

Thanks yes a did fit the new pump.
And the oil is fine on the dipstick and the oil filler cap

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[EmilysDad]

no 'mayonnaise' on the filler cap or on the dip stick isn't a guarantee that the head gasket has not failed.

 

[Jim2]

A common cause of water leaking or Vanishing, on the OM651 engine is the fuel filter housing leaking where it joins the block. Its linked to the engine coolant system in order to heat the fuel before it reaches the injector pumps but some of these only had two remaining bolts instead of 3, so they tended to leaks Happened with my one.

 

[Graeme 1978]

Thanks all 4 the replys.
The fuel filter was changed to the upgraded 1 a while ago.

So a did another pressure test and a left it to find the leak and a did it's the radiator near to the drain plug so looks like a new rad but hey am happy with that at least it's not the head gasket so much happier now.
Thanks for the help

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[Uncle Benz]

The om651 can be a nuisance for coolant leaks. When replacing the water pump, always fit the complete unit with the back housing attached. The back housing is plastic, and also has a plastic outlet pipe on the back that also distorts and leaks. Often people just replace the front bit without removing the back housing, so they never see that’s leaking too.
Also fuel filter housing, as mentioned, plus thermostat unit. The oil filter/cooler housing also contains coolant, plastic again. I’ve also seen split hoses that go to the EGR cooler, and leaks from the EGR cooler itself.
The heater hose that goes out through the false bulkhead with a quick release fitting on it is another one I’ve seen more than twice. They like to crack.

 

[mioba]

Good points above, plastic and coolant just dont mix, plastic doesnt like heat cycles - it goes brittle.
I learned this from my VW T25, has plastic coolant pipes running from front (radiator) to back (engine). Known to crack and replaced with metal ones.
Why companies dont learn is beyond me.

 

[Uncle Benz]

Good points above, plastic and coolant just dont mix, plastic doesnt like heat cycles - it goes brittle.
I learned this from my VW T25, has plastic coolant pipes running from front (radiator) to back (engine). Known to crack and replaced with metal ones.
Why companies dont learn is beyond me.

^this. I’ve often seem om651’s that have had a waterpump failure and got “a bit hot” suddenly become afflicted with further leaks soon after. It’s because that brief overheating has distorted other plastic items.

 

[Graeme 1978]

Hi can anyone point me in the right direction on how to remove the radiator thanks.
preferably with step by step or pictures would be good.
Cheers