2000 Yukon 5.3 particles in oil, blown headgasket?

[diLucca]

Hello guys.

Does this sludge particles look like antifreeze mixed with oil? Or just sludge after engine flush?
Had some low oil pressure issues before oil change(I forgot to change oil for 2years, but only 3500 miles after last change), so used engine flush and this come out during oil change.
It is not metal shavings, not magnetic and can be crushed.


Engine knock before, and after oil change

I have coolant leak somewhere, which I cant find.
When driving in city(stop/go traffic) after 30min the low coolant warning light came up. If shut engine off for at least 15-20min the warning is gone.
Highway drive for 5hour, no coolant warning.
Also when I wanted to add coolant on cold engine, there is still pressure in overflow tank even sitting for a week, when unscrewed cap, it flew out and coolant level go up.

Tried gas tester in coolant, and all good I think.

In 2021 engine gets litte overheat, when GMB water pump blew out rear pump cover after 1hour. Changed all hoses, pump, radiator, firewall T connectors. Only crossover pipe under intake wasn't changed(old style connecting all 4 corners) and rear heater pipe/hose.
Could it after 3+ years still have air pocket somewhere?

Thank you for any input.

 

[rockola1971]

Coolant pressure in overflow tank after a week of shutdown is not normal. Typically if you have a blown head gasket that leaks oil into your coolant you will also have exhaust gases going into there as well. This will cause your engine coolant temp to warm up really fast and usually hotter than your cooling fan can handle which results in near or at overheating, especially when not moving during the summer.

Typical leaking points are water pump weep hole (look for water marks below weep hole), coolant tees at heater hoses and radiator at the oring seal of the plastic tanks.