BLACK RESIDUE IN COOLANT RESERVOIR

[TRUCKING365]

Hello everyone,

I am new to the forum and trucking in general. I have a 2015 Freighliner Cascadia with a dd15 in it. I am currently doing maintenance on the truck and noticed I have some sort of black buildup in the coolant reservoir. I did a couple of google searches and came across this forum. Currently seeking help to determine what the problem might be. Temperature in engine is fine, does not seem to be consuming coolant either. Someone suggested EGR cooler going bad; however, upon checking the hot pipes, they seem to be OK and dry. Any ideas or suggestions as to what it might be? Another thing I came across during my search was the option of injector caps and o-rings gone bad causing diesel fuel to leak into the coolant. I do not know enough about injector caps in order to determine it being the cause. Thoughts? I thank everyone in advance for the help.

[Lonestar10]

If it's ever had the head replaced it could be oil residue left over from that

[tree98]

What does this black residue look like? Can you post some pics of what you're looking at?

[TRUCKING365]

Wow! Thank you guys for the fast response. As far as we know, no head replacement was done. I will take detail pictures this afternoon and post them on this thread. It does not look like oil (oil usually turns brownish in color when mixed with coolant or water). It also does not spell like oil. This stuff looks more like carbon residue. Pictures coming soon.

[marek4792]

It could be injector cups apparently their failure rate is as common as the volvo d13

[Waterloo]

That don't sound good, something is contaminating the coolant. Sounds almost like a head issue, have you checked the coolant system for exhaust gas? If not, NAPA has test kits, they call it their "Block Test kit", and it runs around $50. It consists of a bottle of blue liquid and a big turkey baster. You fill the turkey baster with the liquid and insert in the coolant bottle opening. If any exhaust gas is present, the fluid will turn green. Unfortunately, this test has worked every time I have tried it.

That is where I would start, it is an easy test to do, just make sure the motor is good and hot when you perform the test. When you do test, give it a good ten to fifteen minutes at a minimum while performing. Tape the baster to the bottle if it will not stay put.

If it passes, I would flush the coolant system, check the hoses too for any build up. That will be easy to do as the coolant will be drained out of the system.

And how is the heat working in the cab? Up front? If you are the second owner, maybe there was a head issue where oil and coolant mixed, could be residue in the heater core too.

The air compressor, and I am not familiar with the DD motors, so I am asking, does it have both oil and coolant running through the air compressor? Another place to inspect. Does the truck build air properly, or maybe there is a new compressor on there? Thinking the old compressor may have contaminated the coolant and no one bothered to address that, or change the coolant. I could see a dealership doing that and sending you down the road.

Just off the top of my head.

[hhow55]

On my truck it was the oil cooler leaking.

[Waterloo]

(12-21-2019 )hhow55 Wrote:  On my truck it was the oil cooler leaking.

Good call, I forgot about that. I replaced mine at the first in frame, around 700,000 miles.

[TallBoy441]

(12-21-2019 )Waterloo Wrote:  

(12-21-2019 )hhow55 Wrote:  On my truck it was the oil cooler leaking.

Good call, I forgot about that. I replaced mine at the first in frame, around 700,000 miles.

My oil cooler went bad and done the same thing, oil residue all in coolant. Just another possibility.