Timing Chain Issue???

[dallas_95gt]

I purchased a 2004 Ford Explorer about 2 months ago, 4.0 V6 with 114,000 miles. After owning a ;98 4.0 OHV, I was hesitant about buying a SOHC, but at the time it was whisper quiet. Now, 4,000 miles later, I've developed a rattle. Definitely coming from the front of the motor, and seems to occur at idle and go away when speeding up. Doesn't matter if the engine is warm or cold. I also have a slight miss when sitting at stop lights, no clue if this is related.

Seems to me like this is a timing chain issue. After doing a lot of searching on here, I'm thinking I should replace the chain tensioner. From my understanding, there are 3, one lower and two uppers. Should I change out all 3, or just the bottom one? This is my primary vehicle and gets drove about 2,000 miles a month usually pulling a small camper, so I need to get parts ordered ASAP before something goes bad. Thanks!!

 

[2000StreetRod]

replacing tensioners

Do you have 2WD or 4WD? The 4WD engines have a balance shaft and the balance shaft chain tensioner and guide are prone to failure.

I used to recommend replacing the left and right hydraulic/spring tensioners every 75K miles because the springs weaken with age. But the recently produced tensioner springs seem to be as weak or weaker than the worn ones. It is possible (but not probable) that replacing the left and right hydraulic/spring tensioners will quiet your engine.

At 118K miles I suspect that your primary (crankshaft to jackshaft) chain tensioner or your balance shaft chain tensioner (if you have one) has failed. It takes several hours to replace the primary chain tensioner since the timing cover must be removed. I suggest spending more time trying to eliminate other possible rattle sources before replacing the tensioner: Timing chain rattle resolution process - SOHC V6