"Soap" in my coolant
 

Hello all.
I did a coolant flush and changed it about two months ago. Yesterday, when I removed the cap to check the levl, I noticed that its bottom was covered with a kind of white soap.
Where can this come from? I suspect it can be oil from a leaking head gasket, do you agree with me? Or it is simply rubbish from the circuit?

Thanks!

190E 2.3, 190000kms, 1992

Oil from a leaking head gasket will eventually separate into black or brown spots floating on the coolant.

I suspect you used a commercial detergent flush and didn't get all of it out -- did you drain the block several times? If not, it's probably detergent. Detergent foam would indicate a need to drain and replace the coolant -- you do NOT want it to foam.

If it's oily, though, you have a problem. Note that there is usually some soluble oil in the coolant for the water pump seals. It's normal to see an occasional oil spot a couple mm in diamter floating around in the coolant tank. Soap, no...

Peter