done that on my renault laguna,got a snotty phone call from the better half saying there was lots of smoke coming out from the engine so she called the breakdown people,yep you guess it a nice engine block smothered in oil copeous amounts of it only had a little bit left in the engine,then had to travel 20 miles to buy a new cap coz no one had it in stock,so the moral is triple check youve put it back :)