A bit oil in coolant expansion tank. Time to worry?

[mitch2k]

Today I was doiing some work at my car, and I noticed a bit oil in the expansion tank.

Its like 85 % water coolant and 15% oil... Difficult to explain, but if you put your finger in it deep, then its a bit black , but not that much.

If you open the oil cover lid at the engine, the oil still looks nice black... no traces of water in it...

Is this a normal fenomen, or should I think about a new cylinder head and/or gasket?

[bagpuss]

15% oil in the coolant is certainly not 'normal' and could indicate a problem however, are you sure its oil and not just grubby anti-freeze (which is an 'oily' substance, although this mixes well with water, so unlikely) or even Diesel (also oily) ?

If sure its oil, I would take it for some checks (compression etc) before it gets worse and/or to put mind at rest. If head warp or crack or gasket etc., you might not necessarily have double-cross-contamination (ie water in the oil as well as oil in the water) due to possible location of 'leak' and/or the direction of the pressures involved - but you could have soon if there is such a fault.

Hows the temp holding up ?

[mitch2k]

The temps are perfect, no problem with that...

It look to me like oil, but indeed, it could be something else...
Maybe I could clean the system, and look if it come back after a while...

What is the best way to remove all the water, and cleaning?

Thanks!

[Alexlind123]

Follow the bentley instructions to drain it out, then fill it with normal water and idle to operating temp with the heater on full. Drain the water out. Repeat until water is clear (it shouldnt really take more than once). On the final fill, use 50% water and 50% antifreeze (blue).

[Dr. evil]

i would check the oil too.

[Randell]

yep, that's trouble alright.. i drove my car with oil in the coolant for bloody ages and it was a big mistake.. was caused by one of the last idiot owners fixing a cracked head with what was basically alloy glue.. the coolant eventually corroded a path into the oil channel and then the oil started slowly seeping in.. oil was always clean, and the coolant contamination wasn't severe.. didn't do anything about it until one day a few months ago when the coolant finished tunnelling its way into cylinder 6 and filled it up! hyrdolocked, luckily i wasn't driving it at the time... the head needed 9 alloy welds, $$$ !

not sure if yours will be similar but oil in coolant = bad regardless.

[CarloE34]

Even if it is grubby anti freeze then its a long way back that you changed the coolant Not good anyway.