Proactive or Reactive

[jhill149]

Newbie here... 01 SOHC 4.0 with 200k miles. Any advice on being proactive and changing out the timing tensioners, guides, etc. or just wait for it to go and replace the engine. It still runs great with only a few seconds of "dry start" when it is cold. Had her since new and will probably put at least another 200k on her.

 

[2000StreetRod]

Timing chain replacement interval?

Overhead cam engines require periodic replacement of the timing control components. Most overhead cam engines are interference engines and if the timing control fails valves are struck by pistons. Volvo uses a timing belt and suggests replacement every 70,000 miles. I have never read a Ford suggested replacement interval for the 4.0L SOHC V6. Timing chains could easily last 500,000 miles. Unfortunately, Ford's implementation using plastic guides that significantly deflect the chains have cut the reliability of the timing components in half. The plastic guides were reinforced with metal in upgrades but the right guide assembly still has no metal reinforcement on the traction side. The guides break more often than wearing out and the right guide requires engine removal to replace. When the guides break the timing chain can slip and frequently slips enough to cause valve damage.

All of the timing component upgrades were incorporated in the 2002 models. To my knowledge there were no further upgrades even though Ford chose to use the engine in the 2005+ Mustangs. Engine damage due to the primary (crankshaft to jackshaft) tensioner failure is much less common than damage due to the left or right guide assembly failure. Since you plan to keep the vehicle and already have some indications of wear I suggest that you try to isolate to the source of the start up rattle. I used a rubber hose and a mechanic's stethoscope on mine. From listening I thought it was the left guide but when I removed the right valve cover I learned that the right guide had failed. Upon removing the engine and inspecting the front components I found that the primary tensioner had failed and the left guide was still good. I suggest that you perform a visual inspection since it is much more reliable. You may want to review the procedure at the following link: SOHC V6 Timing Chain Inspection & Repair
I believe that the valve covers are easier to remove on your 2002 than on my 2000 which the procedure was written for. I checked the right one first since if it is bad then the engine has to come out for repair. I installed a pre-oiler after replacing my timing components to increase their reliability.