Black sludge in radiator and over flow help please

[gypsie.amg]

Radiator over flow tank & radiator full of oil like black thick sludge, but not a milky colour it’s black black. No water in engine oil at all or under oil cap. Navara is not getting hot at all, but I think has lost power down low. She always pulls a trailer

 

[Damian m]

Looks like you will be needing at least a new head. You won't know for sure till you strip the top end off the motor.

 

[Scott52]

Radiator over flow tank & radiator full of oil like black thick sludge, but not a milky colour it’s black black. No water in engine oil at all or under oil cap. Navara is not getting hot at all, but I think has lost power down low. She always pulls a trailer

If you have the YD25 diesel it's possibly the oil cooler/heat exchanger that's split internally allowing oil to pass into the cooling system. It's a circular item bolted to the side of the oil filter housing under the filter. It's not too difficult to replace and not that expensive. The easiest way to check it is to remove the cooler and use compressed air. Block one coolant entry and apply compressed air to the other. Use a regulator as you only want about 15 psi. Immerse in a bucket of water and if that is causing the problem you'll see a stream of air bubbles coming out of the centre which means there's a path for the oil and coolant to mix.

You may also have coolant in the engine oil. Oil is less dense than water so the H2O will settle to the bottom of the sump.

 

[Phunk]

If you have the YD25 diesel it's possibly the oil cooler/heat exchanger that's split internally allowing oil to pass into the cooling system. It's a circular item bolted to the side of the oil filter housing under the filter. It's not too difficult to replace and not that expensive. The easiest way to check it is to remove the cooler and use compressed air. Block one coolant entry and apply compressed air to the other. Use a regulator as you only want about 15 psi. Immerse in a bucket of water and if that is causing the problem you'll see a stream of air bubbles coming out of the centre which means there's a path for the oil and coolant to mix.

You may also have coolant in the engine oil. Oil is less dense than water so the H2O will settle to the bottom of the sump.

Had this same issue with a VW TDI, the Oil cooler seals let go and started leaking coolant along with mixing oil into it. Doesn't go milky, just floats up and collects at the top of the radiator / overflow.

 

[Scott52]

Had this same issue with a VW TDI, the Oil cooler seals let go and started leaking coolant along with mixing oil into it. Doesn't go milky, just floats up and collects at the top of the radiator / overflow.

I just had the same problem with my Suzuki GSXR750 motorcycle. The bike's been unused for nearly four years in a hot humid environment. The first start saw oil in the radiator. I did the oil cooler test described above and sure enough there was a stream of air bubbles coming from the centre. The internals had corroded creating a path for oil and water to mix.

It was easy to repair but difficult to stomach the cost of a new genuine oil cooler at $600!

 

[Phunk]

I just had the same problem with my Suzuki GSXR750 motorcycle. The bike's been unused for nearly four years in a hot humid environment. The first start saw oil in the radiator. I did the oil cooler test described above and sure enough there was a stream of air bubbles coming from the centre. The internals had corroded creating a path for oil and water to mix.

It was easy to repair but difficult to stomach the cost of a new genuine oil cooler at $600!

Tell me about it.. Genuine oil cooler for the 3.0TDI was $1300, I ended up getting a Bilstein one shipped from overseas for $350 delivered.