Hi Everyone,

I recently bought a '99 F150 with the 4.6 Triton V8; it's a very clean truck and runs well; but the engine makes a light clacking sound, mainly when you are driving and let off the accelerator. You can hear it when the truck is idling, but only if you pop the hood. It appears to be coming from the top of the engine, on the passenger side, in the valve train. To me it sounds like something sticking for some reason, as it only happens when the engine is not under load. It seems that the engine being under load supplies enough force to overcome whatever it is, and the engine sounds fine.

Any ideas what it is? And what to do about it? I'm thinking to remove the cover from the valve train and look for worn or gummed up parts. The previous owner ran the wrong oil---he ran 10w-30. I replaced it right away with 5w-30 and a Motorcraft filter, but it doesn't seem to have helped. Thanks for any thoughts.

 

Maybe the 10-30 was to try and cover something up...?

It could be something as simple as a tensioner pulley or could be much worse.

Remove the serpentine belt and start the truck, make sure it is none of the pulleys. Eliminate that (reinstall) and move on to a mechanics stethoscope to try and really pin point the sound. If you want to remove the came covers, it's not to hard of a job. While your in there check the timing chain for excessive slack

Video clip with audio would help..?

 

Thanks for the thoughts. I'll check those things out. I'm pretty sure it's not a tensioner pulley, but it can be hard to pinpoint sounds with the fan and stuff blowing. So I'll dc the belt to see for sure. I'll see what I can do about a recording. I don't have a video camera. But my camera will probably shoot a short one. The engine has about 143,000 miles on it. I don't think the former owner was trying to hide anything. My b.s. detector is pretty sensitive; I think he ran that oil because he thought it would be better. The sound is a kind of fluttering sound; it has a crescendo to it and lasts for just a couple seconds or so at a pop when you let off the gas. Although I did hear it very faintly today at times when accelerating and listening for it. Funny thing, I was at a stop light listening when up beside me pulls a Chevy 1500 work van that sounded like a dryer with a bunch of loose change tumbling around in it.

 

Then it sounds like it could be a leaky exhaust manifold gasket (they were common on the passenger side) or timing chain tensioners are bad and the slack is what you hear in the chain.

 

Everything Toyz has mentioned plus suspect a bad lash adjuster and or finger follower, both easy to change.

 

How can you tell if a lash adjuster or follower is bad? What do you look for? And when replacing the timing chain, do you replace just the chain, unless other parts show wear? Or do you replace the rest of the timing parts as a matter of course? I'm pretty mechanical but don't know as much about engines as about other things. So I think I could do it myself, ... but it can't go wrong, or take me an eon, because this is my only vehicle. Sorry I haven't gotten a video up yet. I've been too busy to do much of anything with this since my original post. What Toyz said about the timing chain makes perfect sense, though. Thanks for your help guys.

 

Remove the cam covers and first look at all cam lobes for any damage. That will sometimes be an indication of a follower flopping around. Cams don't always get damaged however so then using your fingers push and rock the finger followers down and side to side. If you find any that move a considerable amount/loose then suspect a collapsed lash adjuster and or a damaged roller/bearings on that follower. You can pop the followers off using a large screwdriver by prying against the follower and twisting the screwdriver upward and outward. The lash adjusters just come straight up and out using needle nose pliers.

If you determine that the timing chain tensioner is defective then remove the front cover and inspect both chains and tensioners etc. Your discretion if you should install new chains but I would replace both tensioners for sure. Read up on the timing sequence of these engines. The 4.6 is not freewheeling meaning you will bend a valve if you don't perform the retiming procedure right. Infact before you even remove the chains readup on the procedure so you don't damage the engine by rotating it with valves open. good luck