What are the symptoms for cracked manifold in a 04 ford taurus

Start car and open hood. Have someone hold a balled up rag over the end of your exhaust pipe. As they do that, listen for the leak under the hood. The back pressure will hiss very loudly if there is a crack. Only do it for a few seconds. The only way to fix a cracked manifold is to completely remove it and have it replaced with a new one, or weld it if the crack isn't too bad.

You might get lucky and it's only a blown gasket.