How to Add Coolant: Cadillac DeVille (2000-2005) - 2004 Click to view0:33Adding engine coolant (also known as antifreeze) to your 2004 Cadillac DeVille is pretty easy. Engine coolant circulates through your engine to keep it cool in the summer but won't freeze in the winter. Make sure to check your engine when it is cold for an accurate reading. Cadillac DeVille Coolant Reservoir | Advance Auto Parts Advance Auto Parts has 7 different Coolant Reservoir for your vehicle, ready for shipping or in-store pick up. The best part is, our Cadillac DeVille Coolant Reservoir products start from as little as $15. When it comes to your Cadillac DeVille, you want parts and products from only trusted brands.