Glc 250d neat oil in the coolant

[Bruce3103]

Hi all help would be massively appreciated, I’ve got a glc 250d OM651 engine which has got neat jet black oil in the coolant tank, any help would be greatly appreciated , it’s 2016 with 35k miles

 

[LostKiwi]

Not been trying to sell it have you? Adding oil to the water is a favourite scam of some unscrupulous potential purchasers in order to get the price down.

 

[matthew k]

Not been trying to sell it have you? Adding oil to the water is a favourite scam of some unscrupulous potential purchasers in order to get the price down.

Yup, happened to me with a 530d. Luckily I knew what was going on and got rid of them, idiots. TBH they'd point it out after doing it.

Interestingly my oil cooler had gone the year before, it filled the cooling system right up at very high pressure. So could be the cooler?

 

[Wighty]

Hi all help would be massively appreciated, I’ve got a glc 250d OM651 engine which has got neat jet black oil in the coolant tank, any help would be greatly appreciated , it’s 2016 with 35k miles

If nobody put it in there you need to get to a garage as soon as possible buddy

 

[LostKiwi]

Check for water in the oil too. Take off the oil filler and see if theres mayonnaise or brown milkshake there.

 

[joderest]

Unfortunately oil in the water can only mean one thing, it's going to cost.
There must be a leak between oil ways and water ways some where. Head gasket could be a culprit, but any where there is close contact and a seal that could fail.

 

[Uncle Benz]

Oil cooler most likely. Not very common, but not unheard of either

 

[ajlsl600]

I go with cooler as starting point as well.u should be able to remove and test it.

 

[LostKiwi]

A cooler will quite possibly leak both ways. When the engine shuts down oil pressure drops and water pressure in the coolant circuit will push water back into the oil.

 

[Uncle Benz]

Oil pressure is mostly significantly higher pressure than the cooling system. In time, sure, you might get the reverse and coolant seeping into the oil. If it’s early days of cooler failure though, oil in the water is the first symptom

 

[ajlsl600]

I have always been able to make up a. cover,brazed in an old brass tube valve and then p.t the cooler.I imagine benz may have made that procedure more complex than need be,but if the cooler is off the car and leaks with this method its f,d. On older cat coolers one could see the air bubbles coming from leaking cooler tubes, if not too many one could lead block the leaking ones,suspect they are plastic bodied and cheap shxxe matrix so a replacement likely only option.

 

[Bruce3103]

No guys I haven’t been trying to sell it but I’ll bare that in mind thank you and I have got no signs of a blown head gasket, no loss of coolant, no lumpy running, no steam out the exhaust, no overheating , no mayo on dipstick or filler cap literally just black oil in the coolant, I’ve been told it’s more than likely the cooler but to have the cooler tested it’s £35 and I have got a full oil cooler plus filter housing kit with all seals from Mercedes for £94 which tells me it’s a common fault, expected a lot more, just annoyed with such a new car with such low mileage to be expecting such a crappy problem

 

[Bruce3103]

Literally like this, it’s the OM651 engine

 

[ajlsl600]

Lowest bidder on oil cooler design/build in my view or makers defect... i would expect 20 yr if decent inhibitor in coolant.