Blowing a head gasket

We own two Cozy Coupes for the boys to play with outside. They are difficult to self-propel on a smooth paved surface and nearly impossible on our backyard’s thick grass. Commonly, one brother will push the other across the yard serving as the car’s power plant. Trey Davey had been pushing Benji the other day with great effort and realized he had greater leverage the lower his contact was with the car. Once he moved so low that he lost his balance, he chose to position himself on all fours and push the car with his head. This worked well until Benji drove his coupe into the fence post.