Truck just started doing this. Takes about 10 to 15 seconds to start doing it from cold start. I can't hear it with a stethoscope touching the valve cover over each cylinder, and I don't hear it on the block or oil pan from underneath. Nothing from the cats, water pump, or bell housing either. Any ideas? I've heard everything from rod knock to timing chain tensioner to lash adjusters or followers. Going to tear into it this weekend, just thought I would see if anyone had advice on pinning it down, or areas to stick the stethoscope.

 

I'm a big fan of trying the simple things first:

-try removing the belt and running it for a little bit - fair warning your alternator and accessories won't be working so you'll want to avoid running it too long with the belt off.

-if the noise goes away iwhen the belt is off ts most likely one of the belt driven accessories or pulleys.

-check to see if all spark plugs are torqued down properly. Let's hope its simply a plug working its way out. Triton are known to do this - would be awesome if thats it and you catch it before it decides to eject a plug.

-is it louder on the drivers or passengers side? Or the same?

-eliminate an exhaust leak or cracked/warped manifold by checking for dark carbon buildup and missing exhaust manifold studs and nuts.

-Stick a leaf blower or shop vac in the tailpipe and duct tape it on there so you pressurize the exhaust with air. Spray soapy water on exhaust manifold. Cats, collectors, etc. If you see bubbles blowing up, you found a leak.

'-remove the PCV - does that make it louder?

wish I could say I'm some kind of expert but I'm not.. Can't seem to resolve the tick on my truck but hope you can.

Good luck!

 

Could be a wrist pin.

 

Maybe good news here. I took the belt off, no change. I just replaced all the plugs and coils (Motorcraft plugs, dualistic coils. Don't flame me too hard, it did solve a cylinder 1 and 4 miss) so I went back and made sure they were all torqued to 28 ft lbs. No change. I got under it again, and this time I was able to find it. It's definitely coming from the bell housing area. I had to touch the stethoscope to the housing from the front of the vehichle for it to be audible. I'm thinking it's flex plate. Guess I'm gonna drop the transmission.

 

For reference, it was indeed a broken flex plate. Cracked about 1/4 of the way around the bolt holes. I discovered a blown head gasket too and now the engine is out of the truck torn down to the block lol.