I have not drove my chevrolet spark (Beat in India) 2012 around a month, I started my car and it was fine. After approximately 30 kms, there was some mild sound from bonnet. So, I opened the coolant tank and I noticed it is blackish. The engine oil is mixed with Coolant. Also the coolant tank overflowed and spill around the tire. When I checked the engine oil, it is empty in the dipstick. So, I refilled the engine oil temporarily.
Got the same problem in July 2019, but the fluid was not overflow then. So I changed the oil cooler in 2019 and there is no problem so far.
So, what could be the problem now? Head Gasket or Oil Cooler or Thermostat?
Appreciated any advice!!