Engine Coolant Dirty Black

[mattonthesea]

Over winter, on Sweden, I asked the engineers to renew the antifreeze. Today, I checked and it was dirty black sludge deposit inside the top of the filler.

I regularly service all the other usual stuff like oil and filters etc but always asked others to do the coolant. (This time I managed to over fill the oil by about 6mm on dipstick. VP2020)

Any ideas on cause? Do I need to worry?

Thanks

M

 

[Graham376]

Sounds like there's no antifreeze/inhibitor.

 

[vyv_cox]

The orange corrosion product we are all familiar with, red rust, is Fe2O3.H2O. This occurs in unrestricted air. if corrosion takes place in an environment where oxygen is restricted, e.g. in a coolant system, we get Fe3O4.H2O which is black. Maybe that's the cause. As said, sounds like there may be no inhibitor, or it has been depleted.

 

[mattonthesea]

Thanks. Boat coming out in 5 weeks so I'll get it sorted then.

 

[thinwater]

If it had been may years, that is one thing. If it had been only a few, different concerns. If it is oily, could be a bad gasket. High chloride (seawater leak) can cause this. Many, many things.

 

[penfold]

Over winter, on Sweden, I asked the engineers to renew the antifreeze. Today, I checked and it was dirty black sludge deposit inside the top of the filler.

I regularly service all the other usual stuff like oil and filters etc but always asked others to do the coolant. (This time I managed to over fill the oil by about 6mm on dipstick. VP2020)

Any ideas on cause? Do I need to worry?

Thanks

M

Did they ever change it? The colour would have been and should be still vivid, typically a bilious fluorescent green although there are a variety of colours and not much standardisation; the different types should not be mixed, but with such a small volume of coolant that's not much of an issue. Unlikely the corrosion inhibitor would be depleted in such a short time unless there's a gross defect in the cooling system.

 

[ChromeDome]

...there are a variety of colours and not much standardisation...

Very important point.
One of the most common misconceptions is that the color identifies the type or properties of the coolant. Cleverly orchestrated by car manufacturers' marketing who want people to buy everything from their repair shops.

This is completely wrong because every type of coolant comes in every color.

I've switched to Command Heavy Duty Coolant/Antifreeze | Prestone, which universally replaces everything else.

 

[WoodyP]

I would sort it now. You don't say what engine it is but I had problems with wet cylinder liners corroding through the use of antifreeze that wasn't the recommended type. The engine had to be rebuilt.to replace the liners.

 

[RAFFY]

Cylinder head gasket leak from cylinder to coolant passages would turn coolant black. Just a thought from previous experiences

 

[penfold]

Unless there are other symptoms of HGF that's a bit apocalyptic.