got a tapping or light knocking from engine??

[TJ Jake]

Here's something I found in one of my FSM:

[kirkandsylvia]

Well, this morning I started it and I could hear the noise, but not nearly as loud as before I put Marvels Mystery Oil in it yesterday. The noise seems to be faint and then pretty much gone by the time the engine warms up. So I am going with a sticky lifter. I believe Bernie has a good point about the rod bearng. Thanks everyone for their input. It is greatly appreciated. :thumbs_up

[bernie]

my YJ does the same thing, goes away when hot, went away totally after an oil change. It is a lifter and seems to be worse when cold and the engine is nearing oil change time.
If indeed it was a rod bearing as suggested it would not get better or go away under any conditions, in fact quiet the opposite

[kirkandsylvia]

Other item could be a cracked manifold or loose bolt at exhaust flange. When it gets warm the metal expands and seals a minor leak. That's what was wrong with my tj.
My yj had the same sound and symptoms (went away after warm), it turned out to be something in the block, went away after putting thicker oil in it.

I put in some marvel's mystery oil today. Maybe I might get lucky with a lifter not pressuring up. I looked at all the external engine parts like a cracked manifold, but it doesn't seem to have that kind of sound.

[scherf68]

Other item could be a cracked manifold or loose bolt at exhaust flange. When it gets warm the metal expands and seals a minor leak. That's what was wrong with my tj.
My yj had the same sound and symptoms (went away after warm), it turned out to be something in the block, went away after putting thicker oil in it.

[kirkandsylvia]

Need some suggestions..I have a tapping or maybe a high pitch knocking coming from engine after it has been started. I dont really hear it when its idling but when I start to drive it, I can really hear it. The engine has 263k mile on it. After it's warmed up, the noide seems to go away, or at least I don't hear it. I was thinking it might be a collapsed lifter, but someone said it might be a rod bearing going. Would a rod bearing going out make a noise when cold, and then go away after the engine warms up?