1997 Mercury Villager Clicking under hood

I think I have a collapsed lifter in my 1997 Villager. It has 152,000 miles on it. I have changed the oil every 3,000 to 5,000 miles since it was new. What can I do and what can I expect to happen if the noise continues?

If it gets really bad, besides the embarrassment and annoyance of the noise, performance and mileage will begin to suffer, and camshaft damage will probably occur eventually.

Have you tried using a product like “Seafoam” to try and unstick the lifter? Pour a can of Seafoam in the crankcase, leave it in for 50-100 miles, then change the oil. Do not leave the Seafoam in there indefinitely. It may also be wise to treat the engine gently while the Seafoam is in the crankcase. If the engine has a lot of sludge in it, the Seafoam can also stir that up, which could be detrimental.

Are you certain that it is a valve lifter? Sometimes an exhaust leak such as a defective exhaust gasket will allow exhaust to escape and the sound made resembles a clicking noise. A mechanic with a stethascope should be able to tell you what is causing the noise.
I suppose it could even be a frayed belt that is slapping something as the pulleys turn the belt.

Thanks for the feedback. I had the same two ideas. Will check both of them out.