After 20min journey in my car... I let it stand for around 2 hours I then decided to open the oil filler cap and to my horror there was all white creamy substance on the underside (classic sign of head gasket failure) or is it??? I read somewhere it could be a faulty thermostat as my car temp gauge takes ages to reach optimum temp. Or is the gasket actually gone?? If so how much would it cost to repair from a garage?
I have a 1.6i 8 valve on T plate
p.s. the car is driving fine but this is my first astra so I don’t know what fine is lol... it running ok without any major fault.
Thank you for your help