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Old 11-10-2015, 05:39 PM
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'99 4.0 with tapping noise

My issue is a tapping sound proportional to rpms only with the engine under load. I would say it sounds like it's coming from the valve train, based on what I've been told are the lifters in other cars (when low on oil or on first start after an oil change). I don't know how to zero in on it since it only does it with the engine under load (i.e. rolling down the road). When I let off the gas, the noise quietens down even at the same rpm. I would say it also quietens down some after the engine has warmed up.

In previous threads, I've documented low oil pressure and excessive oil loss. Recently completed replacing the oil pump and rod bearings. After completing that, I still have a tapping sound which is hard to diagnose...

What is the best way to examine the condition of the top end? I can pull the valve cover and start taking things apart, but I'd like to know what things to check first... what components in the valve train cause the tapping sound? Is there a good guide for how to inspect the parts?

Thanks in advance...

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Old 11-10-2015, 05:56 PM   #2
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Sounds more like a bearing and if it is it will get worse soon

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Old 11-10-2015, 05:58 PM   #3
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I a tap once, like you when it was under load. Ended up being a exhaust leak that would tap when motor got torqued. Just saying could be many things
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Old 11-10-2015, 07:08 PM   #4
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Was it there before all the other work? It could be a number of things. Do you have any way of posting a recording of the noise? If it was a lifter i would say it would do it all the time not just under load. You could pull the valve cover and see if any of the rocker arms are loose that would indicate a weak lifter. Hell it could even be a cracked piston skirt causing it too.

Keep us posted.

-Jason
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Old 11-10-2015, 07:50 PM
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Video/audio of sound

Here's a video (don't tell my wife I was driving and using my cell phone). This was pretty soon after starting up, but I don't think the sound changed much over the course of my entire 20-minute drive home:

https://youtu.be/KuSps6RxY6k
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Old 11-10-2015, 07:59 PM   #6
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I hate to say it but if i had to guess, I'd say that's a bottom end knock. It sounds way too deep to be a lifter. Sorry.

-Jason
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Old 11-10-2015, 08:00 PM   #7
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You are site no broken piston skirt as you had it apart for rod bearings right
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Old 11-10-2015, 08:19 PM   #8
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Should say you are sure not site
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Old 11-10-2015, 08:27 PM
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Yes, there was absolutely no metal in the oil pan... frankly, I was surprised after reading about piston skirts. I really believe this is in the top of the engine...
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Old 11-11-2015, 05:22 AM   #10
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I would still say its in the bottom, a cracked piston wont necessarily leave metal in the pan, plus its kinda hard to do a complete inspection without removing the crankshaft to see whats going on.

Going back to one of the original posts it was run low on oil to the point engine noise was present, were still dealing with the original problem, In my opinion.

-Jason
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Old 11-12-2015, 12:06 PM
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Drove the jeep some yesterday, and it seemed like the noise may be getting less pronounced (although clearly still there). Once it warmed up, I had a harder time hearing it with the A/C fan on once I got up through 1st and 2nd gear. Last night I moved it around in my driveway and, with it cold, the noise is audible at idle but gets quieter at 1000-1500 rpm. I'm going to continue driving and see if it's just been dry for so long (sat for almost a month while I was doing the bearings and oil pump) that it needs run time to re-lubricate all the surfaces properly. I doubt that's it, but I don't really have any other immediate options. Taking it on a longer drive tomorrow, so we'll see how it does.

Still looking for guidance on how to approach the valve train. I looked online, and didn't see any good YouTube videos on disassembling the rocker arms and removing pushrods. I looked at Section 9 of the FSM and it has very little detail on disassembling the head... so any references would be appreciated.
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Old 11-12-2015, 12:09 PM
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To clarify...

Quote:
Originally Posted by WBN3 View Post
...sat for almost a month while I was doing the bearings and oil pump....
BTW - a good bit of ^that^ time was while I was out of town on business or waiting on parts, or doing research... I'm old and slow, but not THAT slow...
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Old 11-12-2015, 09:17 PM   #13
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WBN3, sitting for that amount of time won't effect anything, I'm not not trying to ride you, but I just hate seeing anyone throw good money after bad.

as for rocker arms and valve lash basically there is none torque the rocker arm shaft and go with it .

-Jason
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Old 12-26-2015, 07:53 PM
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An update

Tearing down the top end due to the continued high oil consumption, and just wanted to update this thread. Some of my research (as well as comments from others) mentioned that one possible cause of tapping/ticking sound was a cracked exhaust manifold... well not sure if that's the only thing going on with this engine, but most definitely did a couple of significant cracks in the manifold. This is one of them:

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Old 12-27-2015, 08:17 AM   #15
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Between that and the cracked piston id say you found the problem

-Jason
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Old 12-27-2015, 08:57 AM   #16
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A mechanics stethoscope is a must have tool, get one, you will narrow it down in minutes.

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