Thread: Black stuff in the Radiator Overflow bottle

I had same issue and replaced my coolant bottle at same time I replaced the oil cooler and coolant. The new bottle is now lightly contaminated at the level mark. I’ve since changed the coolant again and the coolant is perfectly clean. Any crud obviously rises to the top and absorbs into the bottle plastic.

I’ll change the bottle soon as I think it’s just a case of not fully getting rid of the oil residue in coolant after the cooler change.

My tip is don’t immediately change the coolant reservoir. Run for a while after the change and flush and change again as only the tiniest amount of oil makes an impact.

At that age the oil cooler is definitely toast. After that it’s only the EGR coolers but you’d see loss of coolant or other issues as a clue.

In saying that yours is very very dark. Did you also change the bottle? There’s no effective way of cleaning the old bottles. I did try.

I had scrubbed the bottle out to remove the residual gunk, but this time is looks like carbon. Could it be the EGR?

Might be a good excuse to blank the EGR's and complete the EGR coolant hose removal...

Originally Posted by PerthDisco

There’s no effective way of cleaning the old bottles. I did try.

I'd love to know what that stuff is. I tried acids (Sulphuric, Hydrochloric, Nitric & Phosphoric), Finish dishwasher powder (basically Sodium Carbonate), Sodium Hydroxide and plain old washing up detergent. One at a time of course.

Next up is Trisodium phosphate and then Pirhana, and I'll give those a go next service.

Regardless, of the chemical the bottles have so many chambers just getting it flushed properly is a mission!

re soot, yes the egr heat exchange has failed internally, while i dont recommend it, while its running with the cap off you can smell the exhaust, more common on the 3.0 D4

Originally Posted by DazzaTD5

re soot, yes the egr heat exchange has failed internally, while i dont recommend it, while its running with the cap off you can smell the exhaust, more common on the 3.0 D4

This likely explains my blackened coolant fresh after a change? 3.0L D4? Any way to diagnose which one given their ridiculous cost?

I'm getting ready to change the oil cooler in my D4 2.7. All parts are here and I'll replace the water outlet (was replaced with timing belt) for good measure at the same time and have a new expansion tank as well. Will also change teh water oulet on the side of the block.


Jobs going to be a pain and take a few flush's I imagineto get rid of all the oil but hey, has to be done.

Oil floats, you can use Omo to break it down. Or you can use Cummins restore. The best way to get it out is float it out.. Make a t peice in was bottom hose and use the garden hose to push it out while the engines running.

Originally Posted by josh.huber

Oil floats, you can use Omo to break it down. Or you can use Cummins restore. The best way to get it out is float it out.. Make a t peice in was bottom hose and use the garden hose to push it out while the engines running.

Cheers mate, so bottom hose where the thermostat housing is?