Help Diagnosing Engine Knock


Skylinessuck

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Sounds like a plan. I asked about the gasket because there is a style that is rubber on a metal core that is reusable and easier to deal with. On the zddp, I recommend it but to be clear, it won't ever fix anything. It would only prevent damage. If it's already fubared from that, it's already toast. Still, zddp in the oil you run seems like a good decision at this point too me. Fingers crossed for ya man!

Oh yeah, one other thing you might look at is pulling the valve cover and inspecting the the push rods and rocker arms. Just because easy and another potential source of noise. Could also help show a dead lifter/cam lobe.
 
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The Goblin

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Sounds like a plan. I asked about the gasket because there is a style that is rubber on a metal core that is reusable and easier to deal with. On the zddp, I recommend it but to be clear, it won't ever fix anything. It would only prevent damage. If it's already fubared from that, it's already toast. Still, zddp in the oil you run seems like a good decision at this point too me. Fingers crossed for ya man!

Oh yeah, one other thing you might look at is pulling the valve cover and inspecting the the push rods and rocker arms. Just because easy and another potential source of noise. Could also help show a dead lifter/cam lobe.
Ah, gotcha. Yeah the Fel-pro one I got is the rubber kind with the metal core. It was really easy to work with, especially since it comes with the studs that you can screw into the block that the gasket snaps to to keep it in place while you seat the oil pan. That was really nice.

And yes, thanks for clarifying about the ZDDP. That's what I meant to say. If the damage is done, the damage is done, I'm just thinking of prevention for the future. Since everything seemed to be ok underneath the engine, I would really like to keep it that way ya know? Thanks for all the help man, I really really appreciate it.

I think pulling the valve cover is a great idea. Since I now know the bearings are ok, it's time to start looking at the next items on the list, lifters being at the top. I've seen a couple of videos on YouTube of guys that had removed the cover and were able to spot the problem pretty quickly. I think it's definitely worth a look. I examined the cam lobes as best I could from underneath, and they really all looked good. None of them seemed to be flattened out at all. Could there still be a stuck lifter if the lobes are good? Not sure how that all works. Any, Thanks man!
 
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The Goblin

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Ok, update for you guys. I got everything buttoned up underneath last night at about 1:30am. I must say, getting the exhaust back on is a total nightmare. Trying to get the flanges connected between the cats and the manifold is murder! It took me easily 1.5 hours of ratcheting the bolts about 1/16 of an inch at a time. I had to use a special socket set I have that is really flat. It's an ingenious set really and it helped a TON with the exhaust, both removing and re-installing. I will take some pictures of some of the tools that helped me most through this part of the journey and post them here. That flat socket set was really amazing.

Anyway, went out today to finish the last few things so I could start it up (serpentine belt, spark plugs/coil bar, etc.). I put in Mobile Super Synthetic 10w-30 with a bottle of Lucas ZDDP additive and then fired it up. It sounded TERRIBLE! Here is a quick video:

I didn't get it in the video, but I climbed underneath and saw exhaust just pouring out of the the connection where I bolted up the exhaust last night. Needless to say I was quite discouraged. So I shut it off and went inside for our nightly family prayer before the kids go to bed. After about 20-30 minutes I just decided to go back out and start it up again and see if out of some miracle, something changed. Well it did! All those crazy sounds were gone! And the exhaust leak was gone! You can hear the difference here (but you can still hear the knocking sound):

I think what happened here is that when I hooked the exhaust back up last night, the metal was cold, and then today when I turned the engine on, it heated up the metal allowing the two ends of the pipes to flex and seat themselves together better. Then the pipes cooled down and contracted solidifying the seal. A good lesson learned here for working with exhaust pipes: Let them warm up and cool down before casting any sort of judgment on whether they are connected or not, especially in areas that don't use a gasket, like this case.

So we decided to take a late night test drive to see how things would go on the road. So my wife, daughter, and I piled in and went out for a drive (it was a beautiful night!). I am pleased to say that it drove better than it ever has. It had more pep and ran quieter and more smoothly than ever. I wonder if the timing was off because of the stretched chain and maybe that affected the performance of the engine. The knocking sound actually got really quiet after only a short time driving, almost inaudible really. After about 20 miles we headed back home. I recorded a video of how quiet the sound had become. I could barely even hear it:

I didn't record it in the video, but I poked around underneath with the stethoscope to see if anything had changed. I can definitely hear some "clicking" on the bottom of the bell housing with a similar. but a little more muffled, sound coming from the engine block at the rear of the engine, off to the side of the oil pan, same places I could hear the sound before I tore into the engine. It was much quieter this go around though.

So, my thoughts? About what I expected. I honestly fully expected the knocking sound to still be there after all this work on the bottom of the engine because nothing I found inside would explain the sound. I'm glad that everything was ok internally, but it means the exploration will continue.

As I posted earlier, I did spray paint the torque converter bolts so I will be able to see if the bolts are hitting the dust cover (the pain would be scratched off if so). This would indicate a cracked flexplate.
IMG_0358.JPG


Needless to say, the test drive was great. It was a beautiful night and the Jeep performed well. The knocking sound is still present, but considerable less noticeable. Not sure why really, but it is what it is. We will keep going until we figure it out.

And just for kicks, here's a quick shot from our drive tonight of the super moon reflecting off the waters of the Great Salt Lake:
IMG_0372.JPG


Thanks again guys. You have all been such a great support. I'm going to drive it for a few days and see if things change at all before I dive into the next project, which I think will be removing the valve cover to get a look at the push rods and rocker arms.

How's that for a great band name? Push Rod and The Rocker Arms?? Lol ;)
Rod Bearing and the Crank Journals?
Cam Shaft and the Lifter Lobes?
Anyone?

;)
 
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The Goblin

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Also, here is the last video of the underside of the engine before I put the oil pan back on. You can see the new timing chain, some of the lobes on the cam shaft, and I show which bearings I checked. This is a little longer, about 5 minutes.
 

pagrey

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If you can barely hear the sound it was probably the chain. Yours sounds similar to mine now and I don't worry about it. The timing chain can cause cam timing scatter which can hurt performance. I'd change the oil and filter again pretty soon to get all the crud out. Great you got it up and running again, that's a big job.

Edit: I'd be tempted to run 15w-40 diesel oil, probably cheaper than the 10w-30 and zddp additive and thicker might quiet it down even more
 

Skylinessuck

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If/when you l the valve cover, I would suggest pulling all the spark plugs and checking each push rod and rocker for play when the cam is on its base circle after it's sat overnight. There shouldn't be any. You can put both rockers for each cylinder on the base circle (one cylinder at a time) by manually turning the engine over via the crank bolt and go like 1/4 past when you see the intake rocker open then shut. It's lot easier to turn the motor over with the plugs out and it gives you a good excuse to change the plugs anyways. Don't forget to number the plug wires ;)
 
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The Goblin

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If you can barely hear the sound it was probably the chain. Yours sounds similar to mine now and I don't worry about it. The timing chain can cause cam timing scatter which can hurt performance. I'd change the oil and filter again pretty soon to get all the crud out. Great you got it up and running again, that's a big job.

Edit: I'd be tempted to run 15w-40 diesel oil, probably cheaper than the 10w-30 and zddp additive and thicker might quiet it down even more
Thanks. It definitely runs better now. It's really quite amazing how smoothly it runs. The sound is still there, but it definitely gets quieter the longer I drive the Jeep. How long do you think I should drive it before changing the oil? 500 miles? Less than that?

I've read a lot of stuff about oils and I've seen a lot of people post that they really like the 15w-40 diesel oils in these 4.0 engines. One diesel mechanic commented on another forum that the 4.0 is basically just a smaller version of the big diesel engines anyway. Quite intriguing...

If/when you l the valve cover, I would suggest pulling all the spark plugs and checking each push rod and rocker for play when the cam is on its base circle after it's sat overnight. There shouldn't be any. You can put both rockers for each cylinder on the base circle (one cylinder at a time) by manually turning the engine over via the crank bolt and go like 1/4 past when you see the intake rocker open then shut. It's lot easier to turn the motor over with the plugs out and it gives you a good excuse to change the plugs anyways. Don't forget to number the plug wires ;)
Ok cool. Thanks. I've seen a videos where people were checking the rods, and if I'm understanding you and those videos correctly, the rocker arms and the push rods should be solid, right? I shouldn't even be able to move them at all by hand, right?

I think this is what the plug wires look like on a 2002, easy to keep track of.

View attachment 159661
Oh snap. Didn't think about the year. Yeah, that'll make it a bit easier!
Lol! Yep! This is what mine looks like! It's kind of a pain even getting the thing off!

So since I've been driving it now for a few days, it's really been running smoothly. I'm very pleased about that. I've been keeping my eye on the oil pressure just to make sure everything is ok there and it has been great except for one weird occurrence: I put the Jeep in reverse to back out of the parking spot at a store and suddenly I got a loud buzzing sound and the light on the Jeep said "CHECK GAUGES." I freaked out for a minute, and then freaked out even more when I saw the oil pressure at ZERO! I quickly put it in drive and pulled back and put it in park, then the pressure gauge went right back up! I jumped out and looked underneath half expecting to see a pool of oil somewhere, but I saw nothing. Totally dry. I've driven it maybe 30 miles since then and it has been totally fine. I'm not sure where the oil pressure sensor is, could I have bumped it possibly while working on all this stuff?

The pressure has been running anywhere between 20-50psi, depending on the load on the engine.

Oh, and for the very first time ever... I took the top off! ;)
IMG_0385.JPG
 
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Skylinessuck

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Correct, no play. There are procedures for checking lifter preload but for your purpose, no play when it's on the base circle. On a '98 the sensor is at the back of the motor near where it mates with the tranny about level with the distributor.
 
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bromel

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Great job! That 4.0 sounds great. My guess is the noise is better because of the oil change/zinc additive. That knocking noise is a bit more pronounced than my TJ and Cherokee—my noises are quieter and more erratic, clack clack clack... clack...... clack.... clack clack clack, but sounds just like your last video when fully warmed up. Curious to see how the zinc continues to affect the noise. And maybe simply removing the valve cover and replacing one of the rockers can fix the problem.

If the noise indeed ends up being the lifters, you can just live with it if you want to and see how it's affected by various oils. Just don't get too liberal with the ZDDP additive, as it is known to mess up catalytic converters.
 

pagrey

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In some countries 15w-40 is recommended by Jeep, who knows why but I run it all the time now. I used to run 10w-30 in the winter when it was cooler but she ain't exactly a spring chicken anymore. I don't know how long I'd wait to change the oil again, I don't really have enough experience with this sort of thing to give anything but a random guess.
 
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The Goblin

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Great job! That 4.0 sounds great. My guess is the noise is better because of the oil change/zinc additive. That knocking noise is a bit more pronounced than my TJ and Cherokee—my noises are quieter and more erratic, clack clack clack... clack...... clack.... clack clack clack, but sounds just like your last video when fully warmed up. Curious to see how the zinc continues to affect the noise. And maybe simply removing the valve cover and replacing one of the rockers can fix the problem.

If the noise indeed ends up being the lifters, you can just live with it if you want to and see how it's affected by various oils. Just don't get too liberal with the ZDDP additive, as it is known to mess up catalytic converters.
Thanks! The sound is definitely still there, but the engine runs a heck of lot more smoothly now. I think changing the timing chain had a lot to do with that. I will keep you guys posted on how things go with the oil changes and what I find when I pull the valve cover. I read that the ZDDP can be toxic to the cats, I'm going to see how it goes. I would rather change a cat than an engine! Lol.

In some countries 15w-40 is recommended by Jeep, who knows why but I run it all the time now. I used to run 10w-30 in the winter when it was cooler but she ain't exactly a spring chicken anymore. I don't know how long I'd wait to change the oil again, I don't really have enough experience with this sort of thing to give anything but a random guess.
Oh really? They recommend 15w-40? Weird. I wonder if those are in countries where catalytic converters aren't required? Because of the zinc content in the oil? Interesting. I've been reading that a lot of the diesel oil manufacturers are going to be removing ZDDP as well because they may be regulated more heavily in the future. An additive may be the only way to get ZDDP in the future. We will see. Thanks man.
ZDDP won't affect engine noise unless something is already seriously f'd up.
Yeah, agreed. What are your thoughts on Rislone? I've seen people adding that to free up stuck lifters.


So the oil pressure problem happened again yesterday. I stopped to get gas and when I started the engine back up again the warning light went on and the gauge was at 0. Just as the previous time, the gauge climbed back up to normal pressure pretty quickly and stayed at normal pressures for the rest of the drive. You guys got any thoughts on this? I know main bearings can affect oil pressure, but all I did was replace relatively good bearing caps with brand new ones. I checked the clearances with Plastigauge before I closed everything up and the clearance was perfectly within factory specs so I can't imagine I did anything that would screw up the pressure on just that one bearing. I found where the oil pressure sensor is on the block and it's right under the spark plug rail where I was banging things around trying to get that rail out of the way. There is a chance I knocked the wiring loose on the oil sensor or something. I will go check it today. But, any other reasons an oil gauge would act like that?
 

reddvltj

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Thanks! The sound is definitely still there, but the engine runs a heck of lot more smoothly now. I think changing the timing chain had a lot to do with that. I will keep you guys posted on how things go with the oil changes and what I find when I pull the valve cover. I read that the ZDDP can be toxic to the cats, I'm going to see how it goes. I would rather change a cat than an engine! Lol.


Oh really? They recommend 15w-40? Weird. I wonder if those are in countries where catalytic converters aren't required? Because of the zinc content in the oil? Interesting. I've been reading that a lot of the diesel oil manufacturers are going to be removing ZDDP as well because they may be regulated more heavily in the future. An additive may be the only way to get ZDDP in the future. We will see. Thanks man.

Yeah, agreed. What are your thoughts on Rislone? I've seen people adding that to free up stuck lifters.


So the oil pressure problem happened again yesterday. I stopped to get gas and when I started the engine back up again the warning light went on and the gauge was at 0. Just as the previous time, the gauge climbed back up to normal pressure pretty quickly and stayed at normal pressures for the rest of the drive. You guys got any thoughts on this? I know main bearings can affect oil pressure, but all I did was replace relatively good bearing caps with brand new ones. I checked the clearances with Plastigauge before I closed everything up and the clearance was perfectly within factory specs so I can't imagine I did anything that would screw up the pressure on just that one bearing. I found where the oil pressure sensor is on the block and it's right under the spark plug rail where I was banging things around trying to get that rail out of the way. There is a chance I knocked the wiring loose on the oil sensor or something. I will go check it today. But, any other reasons an oil gauge would act like that?
I would suspect a pressure sensor/sender problem or a wiring connection issue. If you were in fact loosing oil pressure it wouldn't come and go sporadically.
 

Skylinessuck

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Sounds exactly like you bumped the sensor and not a real problem.

Not sure about the Rislone. Never used it but I'd suspect it's the same thing as Seafoam.
 

brewtus98

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Interesting I find this thread. I just joined. Chasing the same knocking described in original post on my daughter's '03 with 149k on it. Dropped the pan, found nothing loose just like OP. Timing Chain has a lot of play so I think that is the culprit. I plan on changing it at some point. So the timing chain likely problem?
 

bromel

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Interesting I find this thread. I just joined. Chasing the same knocking described in original post on my daughter's '03 with 149k on it. Dropped the pan, found nothing loose just like OP. Timing Chain has a lot of play so I think that is the culprit. I plan on changing it at some point. So the timing chain likely problem?

No, OP changed the chain and the noise remains.
 
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The Goblin

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Hey, sorry guys. Sorry I haven't updated in a bit, I've been busy enjoying the spring weather with the top off. :) My family and I have taken a ton of quick impromptu drives out through the farmlands lately just to enjoy the scenery. It's been awesome. We took a picnic out to Antelope Island (a large island in the Great Sale Lake that you can drive to) just this weekend and got caught in one heck of a summer rain storm! We laughed the whole way back while getting pelted with warm rain in a topless Jeep. It was a blast. (the funniest part was when I was so confused as to why the windshield wipers weren't working and then I finally realized it was because the water was on the INSIDE of the windshield! Lol!). Anyway, some responses and updates:

I would suspect a pressure sensor/sender problem or a wiring connection issue. If you were in fact loosing oil pressure it wouldn't come and go sporadically.
Ok, thanks. That's what I'm thinking too. It has only happened once since and it only happens for a second and then goes right back up. Now that I know where the sensor is located, I'm sure I bumped it when I was messing with the spark plug rail thing. I will check it out to see if I messed with the connection.

Sounds exactly like you bumped the sensor and not a real problem.

Not sure about the Rislone. Never used it but I'd suspect it's the same thing as Seafoam.
Ok, thanks for the input the too. It was freaking me out a bit since I had messed with some main bearings, but my nerves have calmed a bit now. I was kind of thinking the same thing about the Rislone. Can't imagine it's much different than SeaFoam really. Thanks!

Interesting I find this thread. I just joined. Chasing the same knocking described in original post on my daughter's '03 with 149k on it. Dropped the pan, found nothing loose just like OP. Timing Chain has a lot of play so I think that is the culprit. I plan on changing it at some point. So the timing chain likely problem?
Hey! Welcome aboard! This has been quite a journey, I hope you can find some answers for your problems here too. If you find anything that I haven't found yet, please post it here! I did change my timing chain which definitely helped the performance of the Jeep, but didn't clear up the knocking sound. I didn't expect it to since my knocking sound is coming from the rear of the engine whereas the chain is at the front. If your knocking sound is at the rear, then I would guess the chain is not the cause either. If you are going to change it and don't want to remove your radiator, get the pulley tool from Harbor Freight. It has a much shorter bolt that will fit in between the crank pulley and the radiator, the ones you can rent from O'Reilly and Autozone have a really long bolt and can only be used if the radiator is removed, assuming your setup is the same as mine.

If it's loose it's adding to the noise, that much is certain. The only way to see if that's all that's wrong is to replace it. Fortunately it isn't too big of a job.

Totally agree here. Mine definitely added to things, just wasn't the core issue (haven't found that yet).

No, OP changed the chain and the noise remains.
Yep. This is the truth. Changed mine (glad I did), but the sound remains.

Update: I had to take it in to have a seal replaced on the transmission that was leaking. I had AAMCO take a look at things for a different problem I was having (lurching = solved = bad PCM/TCM), and they changed the shift solenoid thinking that was the problem. The seal they put in was leaking so they fixed it for me. So I finally got it back and I think I'm ready to start the next phase of investigation. Honestly guys, I'm leaning towards an exhaust leak, probably from the manifold itself. I found another video on YouTube of a guy with a really similar noise and it turned out to be an exhaust leak for him. So I think I will do the "shop-vac-in-the-tail-pipe" trick and see what I can find with a bottle of soapy water. I did some spying underneath and I think I can see a spot on the manifold, right at the rear, where it looks like exhaust has been escaping (black marks around the manifold). So it may blown a gasket, or maybe the manifold itself is cracked. That could explain why the sound is loud when the engine is cold and it almost completely goes away now when things warm up after a few miles. If the metal gets hot and expands and closes up the leak, that may explain it.

So I will try that and see what I find.

I think I will also take off the valve cover and see what I can find underneath, see if there is any play in the rockers, like you guys mentioned.

It's also time for another oil change to see if there is still glitter in the oil. I'm really hoping it will clear up after a few changes and it was just residual crap that was trapped in the carbon over 18+ years, possibly from the chain wearing. Although, the glitter definitely has a copper tone to it and I'm not sure what would be copper in the engine...