Just another 4.0 tapping and knocking thread

B

bobbylx

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Hey all, hoping I can get a little guidance on this.
I’m not completely new to the 4.0 or knocking and tapping. My XJ threw a connecting rod once and then broke a piston skirt so I do have some experience with that. This one has me stumped though. It started two days ago while driving. Nothing out of the ordinary just flat ground nice slow speed of about 35 when all of a sudden it just started making this tapping sound.
It was due for an oil change so the first thing I did was drain the oil and remove the filter. The oil was drained into a clean pan. And then ran it through a piece of panty hose and found no metal shavings. I drug a magnet through and also did not come out with anything. The filter was clean as well. I used an extension magnet and stuck it into the oil pan to see if anything would come out and again nothing. So I put fresh oil and filter back on, and then started with the top end. I removed the valve cover and checked all of my rockers and push rods. The rockers were all tight with no play, and I could twist the pushrods easily but none of them had any play or issues. I ran the engine with the valve cover off but still could not identify the sound. Next I checked my flex plate and all the bolts were in and I saw no visible cracks and there was no play in the flex plate. I’ve looked at the exhaust manifold the best I could and I see no cracks or loose bolts. But Because it is so hard to see I am not completely certain the exhaust manifold is 100% OK. I will come back to that tomorrow I guess. Are there any other suggestions short of dropping the oil pan to inspect the bearings and pistons?

 
Your lifter is stuck, they often stick if you push oil change intervals. Try another brand or type, for example switch to valvoline or to synthetic, or the other way around. I use 15w-40 in hot weather and it works great. That tick wont hurt anything, I wouldn't start pulling stuff apart for at least another two or three oil changes. It would have to slap way harder than that to start damaging the cam.

(could be exhaust, for me it's easy to tell in real life if you get under the manifold but difficult to tell on video)
 
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I'd pay close attention over the next week or so when it makes the tick, that'll really help you determine what it is. You could also get a stethoscope, they are cheap at auto parts stores. If you can't easily hear an exhaust leak vs a lifter you will with one of those.
 
Not sure what the previous owner ran but I switched to Mobil1 full synthetic 10w30. I’m happy to let it idle, short drives to see if it unsticks. I should also mention absolutely no change in power or driving. Oil pressure is still perfect.
 
If it's not exhaust then I'd switch to conventional and see how it does. Our engines don't need synthetic unless you have really cold temperatures but use what works for you.
 
Had this EXACT same issue but unfortunately shortly thereafter my radiator blew and I was unable to pull over, so I blew a head gasket, warped the head, and had a connecting rod bend. Ended up replacing the motor. If you have free time I wonder if you could pull the head and see if you have a lifter that’s stuck, or a push rod or rocker loose I know some people have had that happen. Best of luck.
 
Sounds like a diesel... maybe you have a diesel engine.

This happened to me. Thought i had a jeep with a 4.0....
Turned out to be a miata.


Or @pagrey is right in post #3.
 
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As silly as this is, I had a sound close to that and found a snapped bolt between the muffler pipe and down pipes. Fixing it has been on my list, but as a temporary fix there’s a vice grip (with taped handles) just behind my skid plate that’s been there for a year now.

It’s one of those “temporary” fixes.
 
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Switch to Castrol Magnatec 10w-40, It is recommended for TJ,s, Its the only 10w 40 recommended as suitable for 10w-30 use!
Quality oil is the way to go.
 
So I've ruled out an exhaust leak at this point. I'm left with either a stuck lifter or some other internal damage. Is there a way I can confirm a stuck lifter without completely tearing it down? Maybe removing the valve cover and checking the push rods or something? I will eventually strip it down to repair it, but it could be a while and I don't want to pop the head off and leave it that way for months.
 
Well, I have identified the source of the noise. Went out this morning and removed the exhaust downpipe and then dropped the oil pan. Found this nice chunk of piston skirt laying in the bottom. The silver lining is that there were no shavings in the oil pan at all. A visual of the cylinder looks like it is in good condition and I saw no other damaged pistons. So she will be put under the carport for the winter and this will be my fall and winter project.
21008D12-27C3-45AD-B73A-9875E2D40699.jpeg
 
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