Need advice before teardown

[cooljoebay]

1996 Explorer 4WD 4.0 (pushrod)
I got this thing which has been sitting for 2 or 3 years. They said that the knocking came out of nowhere one day and it's been sitting since then. I dont know how true that is.

The knocking is a high pitching "tapping" sound coming right from the top center. If you give it gas it's faster and louder. It's a constant tap...sounds like someones inside there tapping on the intake with a wrench. Its one single sound. I drained the oil and put a new motorcraft filter and more oil. After reving it a few times the tapping sound tries to go away at idle speed. The sound is ocassional if anything. But if I give it gas at all the sound is very prominent(again). The other thing is that when the tapping sound tries to quiet down at idle, there's a faint lower pitch sound that shows up...it only happens when the high tap fades off. But all the sounds "seem" to come from the top end.

I was thinking maybe i will have to remove the valve covers to check it out.

What do you think about this? Is there something else to try before tearing into it?

 

[Heavymentill]

Sounds like worn rocker arms.

 

[KurtAbbott]

leak around the header possibly? I had something very close to what you describe and found the last header bolt on the passenger side was loose.

Kurt

 

[cooljoebay]

Thanks for the replies. The only thing i haven't checked is all the spark plugs. I'm betting THAT isn't the problem. But the rocker arm problem is the same thing my dad says. He thinks it sounds like a rocker arm could be loose or a compromised lifter. Guess i'll have to start taking stuff off. I'll keep this updated for reference to help others.

Thanks.

 

[Norad]

Start by taking the valve covers off and looki at the rocker arms. I had the same problem in a '96 4.0 chrand cherokee and what it came down to was a "semi crushed lifter". I figured it would be better to get rid of the POS and get an X instead of taking the time to pull the motor down and fix the problem.

 

[cooljoebay]

Thanks. I´ll definitely post what I find out. I fixed the frozen lifgate problem by unjamming the mechanism after removing the inner panel. And after a torturous attempt to fix the ¨door ajar¨problem I gave up and pulled out the fuse. I´ll gladly go without a speedometer until I figure something out with that. For a truck that has been sitting for 3 years it fires right up and idles perfectly and is super quiet. Just has the clicking knock. $300 is a good deal(i hope).

 

[cooljoebay]

Obviously, I am a year and a half late on this project. But I got around to it.

I pulled the valve cover on the driver side, which is where the knock was coming from. I found that the pushrod on each end of the rail was worn to an oval shape and actually further up into the rocker arm. I assume this would create a loose pushrod and a lot of racket. All the others looked fine. I am going to replace the two rockers and rods to see if that gets things quiet.

If anyone has any other good advice beforehand I appreciate it.

Thanks.

 

[cooljoebay]

I put in a couple of new rockers and pushrods putting it all back together. It took about an hour surprisingly. Fired up the truck and BAM, the knock is still there. I tried letting it run for several minutes but nothing changed.

The high pitched tapping sounds just like its coming from under the valve cover on the driver side toward the back. There is also a faint low pitched knock that occurs slightly out of sync with the tapping. I can only speculate a bad lifter but the only way to tell is pull the head. I am not thrilled about doing that. Any ideas would be greatly appreciated.

Also, is my OHV a better engine than the other V6? Can they be swapped? I weighing my options between repairing this lemon or swapping engines.

 

[wood1]

If you search lifter there are many threads where guys have used a commercial engine treatment with good results. I read ( and heard before) of running some ATF in the oil to clean the varnish that is causing the lifter to not pump up properly. Might be worth a try before you yank the head for one lifter.