help debugging engine tapping noise (99 4.0 WJ, 250k miles) - JeepForum.com
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post #1 of 40 Old 01-23-2020, 09:55 PM Thread Starter
breadboard
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help debugging engine tapping noise (99 4.0 WJ, 250k miles)

Hello!
I got my jeep running again after cylinder head replacement and it has the same noise as before (video link below). Initially I thought it was valve tap but does not seem to be the case with rebuilt cylinder head and new seals. Also doesn't look like an exhaust leak. Tried turning on AC and no change, so might not be AC clutch. It's really hard to hear where it is coming from, unsure if it's something in the lower half of engine or maybe water pump / power steering / etc. Any pointers would be highly appreciate. Thanks.

Video: https://photos.app.goo.gl/KrqvmTpky2sq3m6B8

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post #2 of 40 Old 01-23-2020, 11:15 PM
Bigrigr
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Boy, I hate to say it, but that sounds like a rod knock in the bottom end.....Put a long screwdriver to your ear and touch it to the oil pan underneath with the engine running. See if it gets louder in your ear.
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post #3 of 40 Old 01-24-2020, 12:44 AM Thread Starter
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That indeed be bad news. I'm planning to change the oil next so I'll also check used oil for debris and then see about pulling the bottom pan off. Thanks for info.
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post #4 of 40 Old 01-24-2020, 04:52 AM
02Lightning
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Man, that doesn't sound like a rod to me, it sounds too "light" of a tap. Did you change lifters while you had the head off? I would think new lifters would have cured that, but the head has to be removed to change them.

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post #5 of 40 Old 01-24-2020, 09:17 AM
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OK this is a continuation of your post concerning hi idle.

Bigrigr made a suggestion above did you act on that idea?
Its really helpful at isolating noise. A length of broom a dowel or if you want a mechanics stethoscope.

Me I am thinking valve train noise ie lifter OIL flow...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #6 of 40 Old 01-24-2020, 10:01 AM Thread Starter
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Hi 02Lightning,
I am using the original push rods and rockers but re-manufactured cylinder head with valves.

Hi jtec,
Yes this is true! Now that the Jeep idles properly I can hear the noise. I will try to identify where it's coming from while the engine can operate, I likely won't have time to do it until tomorrow which is why no update. I started a different thread because it is a different issue and figured it would be helpful for others to see it this way.

I will look for a stethoscope. Thank you all for input.
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post #7 of 40 Old 01-24-2020, 10:20 AM
FanTech
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Sounds like a rod knock, or similar to my issue: rocking piston.
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post #8 of 40 Old 01-24-2020, 10:30 AM
2oldjeeps
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my 00 xj had clatter at 168k now 179k actually a bit less,
my 99 wj had clatter at 138k now worse at 147k. risolone made it worse.
im just lubing and drivein...

99wj,143,000 miles
00xj,177,000 miles
10hummer3,74,000 miles
98xj,130,000 miles
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post #9 of 40 Old 01-24-2020, 11:37 AM
007matman
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Broken Piston Skirt.

Sorry man.. sounds just like my old engine.

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post #10 of 40 Old 01-24-2020, 07:17 PM Thread Starter
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Hi Gang,
Small update. I was able to get a mechanics stethoscope but don't feel like I'm skilled enough to use it effectively yet, it will take more practice, please don't assume my statements with full confidence. When possible, I tried to press the flat end of the scope on a piece of something flat to get best coupling. It seems like the cylinder head cover and the pan on the bottom of the engine were loudest, the intake manifold and exhaust headers were second loudest, and the engine (cylinder head and block) were the least loud. My feeling is that the rear driver-side section of the bottom pan had the loudest tap noise, but again, I am not fully confident in this.
On a side note, in case anything is important. Checked oil levels just in case (when you are out of good ideas, you try dumb ideas!) and the level was in the middle of safe zone. Also when I replaced cylinder head, I didn't notice any push rods being different from any others. I cleaned them and used compressed air to make sure inside was open. No visible defects on the surfaces and verified that the rockers flooded with oil before I took off the old cylinder head and after I re-installed new cylinder head. Also i made sure to remove and install the rockers by removing/installing the pair of bolts one turn at a time as not to damage the bridge. Finally, I verified that all rockers were under tension by wiggling them with my hand before removal and after installation. I didn't try to do this after trying to turn the engine and did not think to use a gap gauge / piece of metal shim at the time.
My next steps are to try and get better at using the stethoscope by watching some videos and trying it again, hopefully I can come back with better information. Thanks!
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post #11 of 40 Old 01-24-2020, 07:20 PM Thread Starter
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One more piece of information, when I had the cylinder head off, I cleaned the the tops of the pistons with seafoam by turning over the engine until each piston was at highest position, wiping, and making sure I didn't leave any debris between piston and wall. I didn't see any damage to the rings at that time, but that is only looking at the top surface.
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post #12 of 40 Old 01-24-2020, 08:42 PM
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Im not as familiar with the valvetrain in the 4.0 as i am the 4.7, but when you installed the rocker arms, did you tighten them all to a proper torque?Or do they have to be adjusted for valve lash with a feeler gauge or something similar? Did i hear you say earlier that this noise was there Before you took the head off and replaced it?

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post #13 of 40 Old 01-24-2020, 11:04 PM Thread Starter
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Hi Bigrigr,
The tap noise was the cause of me doing a cylinder head replacement because in my lack of experience, I assumed that it just came from the head and I could get it sorted that way. I did tighten the rocker arms to proper torque following the procedure where you alternate turning each bolt one time back and forth. The noise is the same as before I did the "service".

I did not use a feeler gauge to see if there is a gap between rocker arm and valve top, I just tried to move them with my hand and all were in tension. I agree that there might be a gap there, all the rocker arms were reluctant to move before and after the head replacement.

If the group feels strongly, I can take the cover off, sparkplugs out, and then turn over the engine while looking for loose rocker arms (e.g gap between the valve top or push rod ((would have to shake the rod to see if moves)).

Thanks.
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post #14 of 40 Old 01-25-2020, 07:22 AM
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All the rockers are showing signs of oil flow?
All rockers are articulating opening the valve and returning?
When turned OFF all the rockers seam 'tight' ?

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #15 of 40 Old 01-25-2020, 11:26 PM
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I still lean towards something wrong in the bottom end. I just did a 4.7 in a dakota that had spun bearing on number 7 ro, it sounded just like your video. If the noise started up AFTER you did the head, i would wonder more about the valvetrain. But sense the noise was there before, and the head replacement made no difference, then i would be getting ready to pull the oil pan. Is this coil on plug like the V-8? Or does it still have a distributor and spark plug wires? If it is a Rod bearing, you can remove the spark from 1 sparkplug at a time (either pulling the sparkplug wire off, or removing the electrical connector on the coil) and the noise will get softer when you pull the offending cylinder. That will at least give you an idea where you are headed inside the pan.

'00LMTD-4.7l,242hd,D30,D44A,3.73's,True-trac front,Spartan rear,4" short arm lift,JK'sW/32's
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