Noise In Engine

I have a 2001 windstar , with a 3.8 engine. It has a low knocking sound from the top of the engine.You can put your hand on top of the manifold and feel it knocking, like its something in the manifold.It quiets down a little when it gets hot.No problem with it running wise.What could it be?

Most likely a loose inner piece of the upper manifold. You can find many discussiions on this subject on this site. (Some of us feel a bit of RTV will hold it in place.... but not all agree.)

This loose piece may also be telling you of the coming of the dreaded P0171 and P0174 codes ... as the upper manifold seals and isolator bolts continue to loosen. I'd go ahead and buy a set of isolator bolts. The seals may be optional if the old ones are in good shape.... but for a few bucks more you cover all bases.

Also...the front valve cover....The new one that is called out in the TSB has an improved baffel for the PCV.....reducing the amount of oil to get into the intake....and result in carbon buildup in the cylinders.

I have a 2001 windstar , with a 3.8 engine. It has a low knocking sound from the top of the engine.You can put your hand on top of the manifold and feel it knocking, like its something in the manifold.It quiets down a little when it gets hot.No problem with it running wise.What could it be?

I just had the entire upper intake replaced. Cost me $350 including parts & labor. It started as a small knock that would come and go but got louder and louder until it wouldnt stop. And yes you can feel it with your hand. 12ounce is correct it is plastic that some say can be fixed However I chose to replace it due to it being plastic. No sense paying twice.

Have the same problem Took mine apart cleaned it out a little and the sound stop for about 1 month now. but I am sure it will come back. I do have an engine light auto zone said both 1 and 2 o2 sensors are bad. But will most likely will do the TSB .