What Am I Riddles

Question: Paint me up to look real good,
Then take me to the shop to maintain under the hood.
Use a small brush to make no mistake,
Or just replace me with something fake.

What am I?

Question: Thirty white horses stand on a red hill,
First they champ,
Then they stamp,
Then they stand still.

What are they?

Question: If you look at my face there won't be 13 any place.

Question: I stand in one place yet I fill a whole room.
I can be filled with molten rock and come in every hue.

What am I?

Question: I was crucified to keep murders out of the maze. What am I?