Greenish-grey gunk in water header tank

[ChristianR]

Good Morning

We are currently at Ramsgate and due to head back to St Kats. Just checking fresh water header tank and noticed on port engine there is greenish-grey gunk in there.

I should be grateful if somebody could advise me what this is?

Many thank in advance for your help.

 

[duncan]

is it sinking or floating?

if a new engine and sinking then rub some between fingers - granular? possibly casting sand deposits from head reacting with antifreeze to make a paste like substance

if floating then oil based and obviously worthy of further investigation - head gasket?

 

[ChristianR]

I would say floating. I am currently scooping it out - it's more greeny than grey - can antifreeze go off?

 

[duncan]

don't know about degrading I am afraid - but doubt it.

floating sounds like oil............which always sounds bad