I've found some milky residue at the oil cap. Is it normal or is it the head gasket blown?
That depends on a lot of things. If you don't drive much, especially if you are one of those people like my wife who drives 3 miles to work and 3 miles back, you can get an oily residue.
This is because as gasoline burns into the atmosphere, one of the by-products is water vapor. You'll always get a little bit of water vapor in the engine that's mixed with oil and gets a creamy color because you don't drive it hard enough. When you are going 65 on a highway, the engine is running and everything is hot but the water is just going to evaporate and go away. You don't have to worry about it making a mess.
But, if you are still concerned, watch my video "how to tell if your head gasket is blown" and then you'll see if the head gasket is blown or if it's starting to blow. Know that it is a big deal replacing a blown head gasket. So you'll want to pray that it is just normal residue from not driving the car long enough, or not changing the oil frequently enough.
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