In the last model year of the first generation of Mercury's Mountaineer, the 2001 came with either a 4.0-liter V-6 engine or a 5.0-liter V-8 engine. Before replacing the positive crankcase ventilation valve as part of troubleshooting a problem on either engine, perform a quick test. Remove the PCV valve and shake it. It should rattle like a ball bearing trapped inside a film canister. If it doesn't rattle, the valve is stuck and needs to be cleaned or replaced. You can clean the valve by spraying a liberal amount of carburetor cleaner into it. The cleaning solution may unclog the valve. If it doesn't, replace the PCV valve with part No. EV-225 on the 4.0-liter engine or part No. EV-152 on the 5.0-liter engine.
Find the PCV valve on your engine. On the 4.0-liter engine, it is on the driver-side valve cover toward the rear, below upper intake plenum. On the 5.0-liter engine, it is in the back of the lower intake manifold.
Grasp the hose on the valve and pull it off. Turn the valve one-quarter turn counterclockwise and pull it out of the engine.
Insert the new PCV valve into the hole and then turn it one-quarter turn clockwise to seat it in place. Reconnect the hose.
