Hello Grandpa Doug,
Here in England our boot = your trunk and your hood = our bonnet so it would probably be 'take a peek under the bonnet'.
I am sure that in your day this would have earned you a slap in the face from a startled lady
My old gran would never leave the house without her bonnet or some other suitable headwear. She would oft lament the slipping of such standards in the modern world, to the extent that she would attack any young lady who flaunted an uncovered head, with a hat pin.
ttfn
Tony