Light valve a tick on cold mornings.....
 

I have a 1999 Jeep Cherokee with the 4.0 6 cyl., after I bought it I started hearing a light valve tick 1st thing in the morning at start up (when its been sitting overnight) when cold, its only does it first thing in the morning and then completelly goes away when its warmed up.....??? What could it be?? The motor was rebuilt 90,000 miles ago , it has 165,000 miles. Two Mechanics I know said its comon in Jeeps and nothing to worry about, I'm selling the Jeep to a friend in 2 weeks, and I want to make sure its nothing serrious....
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It is just lifters that when they set overnight bleed down,it takes a bit for them to get oil and pump up,it is nothing serious and quite common.

You have one or more lifters bleeding down and losing their prime overnight.

They collapse and pull away from the pushrod. This creates a gap where there shouldn't be one. The noise you hear is the lifter slamming into the pushrod until it pumps back up and takes up the slack.

Not unusual in higher mileage engines.

My '88 Pioneer 4.0 L6 w/127K has been doing this from time to time on cool or cold mornings, even during the Summer months. It's been doing it since around 90-100K or so. I don't worry about it, I figured it was just a sticky lifter and it seems to clear up quick.

What grade and brand of oil are you using?

8lugnuts