Help Diagnosing Engine Knock

First, if that is carbon in the pan then you must have some incredible blow by.
Second, those copper flake in the oil came from the under the soft babbitt on the surface of the bearing. So some where you are going to find a bearing that worn though to the copper layer.
Third, my guess is that you have the main trust bearing gone or a cam bearing.
That bad bearing is not going to heal itself so keep tearing it down till you find the bad bearing.
 
pagrey said:
The chain is sitting right there, just check it and move on. Mine didn't sound anything like yours when it stretched but mine wasn't really really bad.

Unlikely it's the mains unless the crank is broken in my opinion but you can easily check it. Rotate the crank slightly back and forth and make sure it all moves together. Seems to me very unlikely the mains would make that noise.
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Good idea. So... dumb question, what am I looking for when I check the chain? ;) I haven't done any research on that really so I'm not sure what to look for. Just if it's loose?

I agree on the mains. I don't think that's it either. They are super tight, the crank spins just fine, and my oil pressure has never had a problem either, which I hear is a symptom of bad main bearings.

I'm just not sure where to go next, ya know? If the rods and mains are all tight, I don't know what the next step is. It still could be the flexplate, there are a lot of symptoms of that. That just means I have to pull the trans back, and that's a first for me too!

Thoughts on a flexplate vs lifter?
 
The Goblin said:
Good idea. So... dumb question, what am I looking for when I check the chain? ;) I haven't done any research on that really so I'm not sure what to look for. Just if it's loose?
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Just turn the crank and see how much slack there is in the chain. If it's bad you'll be able to push it more than 1/4" easily midway between the gears. It should be fairly tight.

I really don't think it's a lifter and beyond that your guess is probably just as good as mine.
 
pagrey said:
The chain is sitting right there, just check it and move on. Mine didn't sound anything like yours when it stretched but mine wasn't really really bad.

Unlikely it's the mains unless the crank is broken in my opinion but you can easily check it. Rotate the crank slightly back and forth and make sure it all moves together. Seems to me very unlikely the mains would make that noise.
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Could be timing chain. The black stuff in the pan could be parts of the timing chain plastic wear strip and the metal flakes, if silver, could be from the chain wearing against the timing chain cover. But the sound is from the rear of the engine and slapping timing chains make a very distinguishable noise in the front of the motor.
 
It looks like you are doing all the right things to find out what the noise is. And you are very patient and methodical. Good job! (y)

My Jeep sounds just like yours does in the first video you posted, so I am following along and anxious to see what you find.
 
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Bill M. said:
First, if that is carbon in the pan then you must have some incredible blow by.
Second, those copper flake in the oil came from the under the soft babbitt on the surface of the bearing. So some where you are going to find a bearing that worn though to the copper layer.
Third, my guess is that you have the main trust bearing gone or a cam bearing.
That bad bearing is not going to heal itself so keep tearing it down till you find the bad bearing.
Click to expand...
Huh, thrust bearing. To be honest with you that's the first time I have even come across that in my research. But, after seeing your post and doing some research to find out what happens when a thrust bearing goes bad, I think this could be a real potential answer. When I first started hearing the noise, many Jeep owners recommended I check the torque converter bolts because they are known to come loose and knock against the dust cover. Well I checked them and they were tight, so I removed them, applied lock-tite and put them all back in... twice. Well, one of the posts I just read on another Jeep forum said that his thrust bearing was bad and therefor the crank was moving back and forth enough to allow the torque converter bolts to hit the dust cover... that could be why I keep thinking it sounds like the flexplate! Thanks Bill M.! I will definitely check this out tomorrow evening!

As far as blow-by goes, I don't really know. I just cleaned everything with SeaFoam, so we will see what happens with that. I do know this, when I rotate the crank by hand, it sure sounds like the pistons are... "breathing" at me sometimes. Is that normal? Or is that indicative of something else?

pagrey said:
Just turn the crank and see how much slack there is in the chain. If it's bad you'll be able to push it more than 1/4" easily midway between the gears. It should be fairly tight.

I really don't think it's a lifter and beyond that your guess is probably just as good as mine.
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Ok cool. Thanks. I will check the chain tomorrow to see how loose it is.

Bill M. said:
Could be timing chain. The black stuff in the pan could be parts of the timing chain plastic wear strip and the metal flakes, if silver, could be from the chain wearing against the timing chain cover. But the sound is from the rear of the engine and slapping timing chains make a very distinguishable noise in the front of the motor.
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Yeah, I will totally check the chain tomorrow. My only thought again is that the sound is coming from the back of the engine and not the front. But I will for sure check it. Sounds radiate and sometimes can radiate to very strange places...

TJRick said:
It looks like you are doing all the right things to find out what the noise is. And you are very patient and methodical. Good job! (y)

My Jeep sounds just like yours does in the first video you posted, so I am following along and anxious to see what you find.
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Hey thanks! It's definitely been quite an adventure! Lol! I hope this journey can help you too, thanks for coming along! If you find anything out, please share it here so I can learn from you too, ok? Thanks a ton!
 
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Ok, I am now a plastigauge pro. ;)

It was a little intimidating at first, but once I figured out how it works I realized it’s actually pretty easy. So I checked the clearances on the connecting rods on cylinders 6 and 7 and they are totally fine and within spec, thank goodness.

I then pulled the main bearing cap 7, the rear cap, and plastigauged it too, totally within spec. But, I’m super glad I checked it because I think I am going to now be able to prevent a future problem; it looked like some debris most of gotten inbetween the shaft and the bearing because there are some nasty gouges out of the bearing by the connecting tab, like sand or something gouged it. It looks really recent. The good thing is that the crank journal is smooth as can be with no gouges or scoring, thank the heavens!

301C9487-3BF5-44E2-81E7-2F103DF5F0E6.jpeg


I did find an almost imperceptible groove in one of the connecting rod journals, right by the oil hole, but I can barely even tell it’s there with my fingernail and it’s pretty smoothed out. I actually did the plastigauge right over it to see what would happen and it was imperceptible. So I’m not really worried about it.

But, I did find this: a very loose timing chain! If it’s only supposed to move 1/4inch, then it’s pretty stretched!
Not sure this is the cause of the banging (front of the engine??), but it could be the cause of the metal particles! Not looking forward to changing it though...

 
That timing chain is loose, how did the plastic wear strip in the timing chain cover look? You have to use a bar move the crank back and forth to check the trust bearing clearance, the crank will not usually move by hand.
 
pagrey said:
Wow, that thing is toast! Looks like somebody is pulling a crank pulley.
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Lol! Yep! I'm not sure to whether to be happy or depressed. ;) From what I've researched, getting to the timing chain is no easy job, possibly harder than this one so far! I'm glad you mentioned it though, or I would never have even thought to check it. Thanks!

Bill M. said:
That timing chain is loose, how did the plastic wear strip in the timing chain cover look? You have to use a bar move the crank back and forth to check the trust bearing clearance, the crank will not usually move by hand.
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Honestly, I'm not sure what the plastic wear strip is so I didn't think to check it today. I will look it up so I know what to look for, thanks for the reminder. And thanks for the clarification on moving the crank, I will try that out tomorrow and see if it budges at all. I made a mistake in the video and said that the thrust bearing is in the middle main bearing, but I was wrong, according to the FSM it's in the 2nd main bearing. If there is play in the crank, I will be pulling that one and checking it for sure.

I do have to say that that rear main cap was really dirty, especially on the side facing back towards the flex plate. I can totally tell that the rear main seal is bad. I think it's important to change those when we notice oil leaking because it sure looks like it leaks both ways; meaning that oil gets out, but dirt also gets in. Those crazy gouges in that bottom main bearing could have gotten much worse. Luckily, as I said, the crank seems to be super smooth without any scoring, but I will inspect it again when I replace that bearing just to be sure.

I do have to say that I'm glad about the way things are playing out so far. Sure, it would be nice to know what the knocking sound is for sure, it would be nice if it was easily apparent, but I am quite relieved that the bearings, rods, crank, etc, all seem to be in good condition. I love this Jeep and I want it to keep running for a long time.

So I will keep going until I find the problem. So far my possibilities are:
-timing chain noise (But it's on the front of the engine and the sound is at the rear)
-Bad thrust bearing (Crank seems really tight, but will check with a bar)
-Cracked flex plate (no way to tell yet unless I pull the trans)
-Lifter noise (But would you hear this on the bottom of the engine and not the top?)
-Cam shaft bearing? (Not sure how to check this, the camshaft seems really tight though)

Thanks guys!
 
The Goblin said:
So I will keep going until I find the problem. So far my possibilities are:
-timing chain noise (But it's on the front of the engine and the sound is at the rear)
-Bad thrust bearing (Crank seems really tight, but will check with a bar)
-Cracked flex plate (no way to tell yet unless I pull the trans)
-Lifter noise (But would you hear this on the bottom of the engine and not the top?)
-Cam shaft bearing? (Not sure how to check this, the camshaft seems really tight though)

Thanks guys!
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Fingers crossed that the culprit is the timing chain. Still think it's the lifters though :) They're located in the heart of the engine at the camshaft, and the noise can easily reverberate downward. Good luck with your journey! Eagerly waiting the verdict.
 
bromel said:
Fingers crossed that the culprit is the timing chain. Still think it's the lifters though :) They're located in the heart of the engine at the camshaft, and the noise can easily reverberate downward. Good luck with your journey! Eagerly waiting the verdict.
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Thanks bromel! You know this exploration has really helped me get to know my engine better. I honestly thought the lifters were much higher up in the engine, but now that I have seen the camshaft and how close it is to the crank, I realize that you are totally right, the lifters really are right in the middle. And I totally agree, sounds can definitely radiate! I've been reading a lot about using zinc (ZDDP) in the oil to take care of the lifter noise situation, especially for these flat tappet engines. Either using a diesel oil (Rotella T5/T6, Royal Purple, etc.) or an additive (I bought a bottle of Lucas zinc to add to the Mobile Super Synthetic 10w-30 I just bought). Got any experience with that?
 
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The Goblin said:
Thanks bromel! You know this exploration has really helped me get to know my engine better. I honestly thought the lifters were much higher up in the engine, but now that I have seen the camshaft and how close it is to the crank, I realize that you are totally right, the lifters really are right in the middle. And I totally agree, sounds can definitely radiate! I've been reading a lot about using zinc (ZDDP) in the oil to take care of the lifter noise situation, especially for these flat tappet engines. Either using a diesel oil (Rotella T5/T6, Royal Purple, etc.) or an additive (I bought a bottle of Lucas zinc to add to the Mobile Super Synthetic 10w-30 I just bought). Got any experience with that?
Click to expand...

Whether or not you should add zinc to the 4.0 is a huge debate among Jeepers—it's like arguing religion and politics at the dinner table. Personally I don't because I've never had engine trouble with either of my 4.0s running good old 10w-30 (apart from what I believe is the same sound you have, which goes away after a few minutes). My understanding is that modern oils have sufficient anti-wear additives for flat tappets, and that adding zinc additive leads to a buildup of ash on the catalytic converter, eventually destroying it.

Again, just what I've read—I've never experienced this myself.
 
The Goblin said:
But, I did find this: a very loose timing chain! If it’s only supposed to move 1/4inch, then it’s pretty stretched!
Not sure this is the cause of the banging (front of the engine??), but it could be the cause of the metal particles! Not looking forward to changing it though...

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Thats funny. I thought the same thing on mine, even did the same video too. In the end, it wasn't the problem.

https://wranglertjforum.com/threads/4-0-engine-knock.21539/post-366073
My rod bearings didn't look quite as good as yours. Lol

IMG_20190615_184123158_HDR (1).jpg
 
bromel said:
Whether or not you should add zinc to the 4.0 is a huge debate among Jeepers—it's like arguing religion and politics at the dinner table. Personally I don't because I've never had engine trouble with either of my 4.0s running good old 10w-30 (apart from what I believe is the same sound you have, which goes away after a few minutes). My understanding is that modern oils have sufficient anti-wear additives for flat tappets, and that adding zinc additive leads to a buildup of ash on the catalytic converter, eventually destroying it.
Click to expand...

The problem is that the engine oil that is made today is not the same as it was when these Jeeps were new. The average person is not interested in driving around a vehicle that is 23 - 14 years old like a Jeep TJ - which was behind the times to begin with. Yes, the engine oil that is sold today is actually better - but not necessarily for our old-school pushrod engines with flat tappet camshafts.

All modern engines use roller camshafts, and they don't need the higher amounts of zinc and prosperous that older flat tappet cams do. So modern oils are formulated with reduced levels of zinc and phosphorous because it isn't needed anymore for an engine in an average vehicle on the road today. And the reduced amount will also extend the life of catalytic converters, which keeps modern car companies happy. Who, by the way, do not care about us and our old vehicles that are long since paid for. And it seems that every few years the oil companies are reducing the amount of zinc and phosphorous in their oils more and more. How much is that hurting our older engines that were designed in an era that had more?

I don't know how much zinc and phosphorous our Jeep engines with flat tappet cams needs, but if you are into the classic car hobby, it is well known that [higher lift] flat tappet cams won't last very long before a lobe is wiped out from using modern oils. And that is because they simply do not contain enough zinc and phosphorous to protect the cam. Brad Penn and Hemmings both make oils that contain high levels of zinc to protect the older, classic engines. I personally use the Brad Penn in my 1985 F150 [flat tappet cam and carb engine], but it doesn't have a catalytic converter. I have considered using this in my Jeep, but I don't know if the higher amounts of zinc and phosphorous in these oils will harm the catalytic converters in our Jeeps or not.

https://penngrade1.com/
https://www.hemmings.com/classic-oil
 
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TJ2 said:
Oh damn!
How did it got to that stage?
If there is a slight taping sound on mine I get worried.
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Yea, in that thread I talked about hearing a loud knock. And only started the Jeep like 3 or 4 times to show a couple of mechanics the problem. I have pics of the inside of the timing cover posted....and no marks whatsoever indicating the chain was hitting anything. The metal flakes in my oil ended up being the rod bearing. I described being able to grab the rod & shake it & hearing a very obvious click, indicating the bearing was wearing away.

BTW, after rebuilding the engine, I used a special high zinc oil to break it in. Then went back to my usual Napa 10w30 (Valvoline).
 
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bromel said:
Whether or not you should add zinc to the 4.0 is a huge debate among Jeepers—it's like arguing religion and politics at the dinner table. Personally I don't because I've never had engine trouble with either of my 4.0s running good old 10w-30 (apart from what I believe is the same sound you have, which goes away after a few minutes). My understanding is that modern oils have sufficient anti-wear additives for flat tappets, and that adding zinc additive leads to a buildup of ash on the catalytic converter, eventually destroying it.

Again, just what I've read—I've never experienced this myself.
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Ok, thanks. I know it's quite the debate, but I think I'm going to try it out. After I get this all back together... lol.

Airjunky said:
Thats funny. I thought the same thing on mine, even did the same video too. In the end, it wasn't the problem.

https://wranglertjforum.com/threads/4-0-engine-knock.21539/post-366073
My rod bearings didn't look quite as good as yours. Lol
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OOOOHH DANG! That does not look good at all man! Lol! I'm definitely glad to say mine don't look like that! ;)
I saw where you talked about your timing chain too. I don't think it's the source of my knock, but I'm glad I know it's stretched so I can change it while I'm at it. With how my bearings look, it may be the source the metal slivers and glitter for me, here's to hoping!

TJRick said:
The problem is that the engine oil that is made today is not the same as it was when these Jeeps were new. The average person is not interested in driving around a vehicle that is 23 - 14 years old like a Jeep TJ - which was behind the times to begin with. Yes, the engine oil that is sold today is actually better - but not necessarily for our old-school pushrod engines with flat tappet camshafts.

All modern engines use roller camshafts, and they don't need the higher amounts of zinc and prosperous that older flat tappet cams do. So modern oils are formulated with reduced levels of zinc and phosphorous because it isn't needed anymore for an engine in an average vehicle on the road today. And the reduced amount will also extend the life of catalytic converters, which keeps modern car companies happy. Who, by the way, do not care about us and our old vehicles that are long since paid for. And it seems that every few years the oil companies are reducing the amount of zinc and phosphorous in their oils more and more. How much is that hurting our older engines that were designed in an era that had more?

I don't know how much zinc and phosphorous our Jeep engines with flat tappet cams needs, but if you are into the classic car hobby, it is well known that [higher lift] flat tappet cams won't last very long before a lobe is wiped out from using modern oils. And that is because they simply do not contain enough zinc and phosphorous to protect the cam. Brad Penn and Hemmings both make oils that contain high levels of zinc to protect the older, classic engines. I personally use the Brad Penn in my 1985 F150 [flat tappet cam and carb engine], but it doesn't have a catalytic converter. I have considered using this in my Jeep, but I don't know if the higher amounts of zinc and phosphorous in these oils will harm the catalytic converters in our Jeeps or not.

https://penngrade1.com/
https://www.hemmings.com/classic-oil
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Thanks! I haven't heard of Brad Penn oil, so I can check into that. I have heard concerns that many of the diesel oils that were known for ZDDP may be removing it now (perhaps Rotella?), so additives may be the way to go in the near future. But I will check into the Brad Penn stuff.

Airjunky said:
Yea, in that thread I talked about hearing a loud knock. And only started the Jeep like 3 or 4 times to show a couple of mechanics the problem. I have pics of the inside of the timing cover posted....and no marks whatsoever indicating the chain was hitting anything. The metal flakes in my oil ended up being the rod bearing. I described being able to grab the rod & shake it & hearing a very obvious click, indicating the bearing was wearing away.

BTW, after rebuilding the engine, I used a special high zinc oil to break it in. Then went back to my usual Napa 10w30 (Valvoline).
Click to expand...
Honestly that's what I was expecting to see, with as loud as this knock is. But I can't seem to find anything loose at all under there (which is not a bad thing!). I'm going to try and get back underneath today and check the thrust bearing as Bill M. suggested and see if that's the problem. If not, I will change out the one main bearing, the rear seal, and move on. I should probably change the timing chain before I put the oil pan back on, since you have to unbolt the front four bolts anyway... good times!

Anyone know how to check if a cam bearing is bad? I reached up there and grabbed a hold of it and it's the same as everything else, tight as a whistle (whatever that means...lol).
 
Pulling the cam and visual inspection is the only way I can think of. They aren't as delicate as the other bearings btw. I was worried when I nicked mine but was told by several engine builders not to worry. Cam walk (end play) and crank walk should be concerns and checked for sure. Should be able to do that with a pry bar from underneath.

I wouldn't run diesel oil either. That Rotella thing has been Internet lore forever since before they started decreasing zddp in those oils as well. Plus different detergent packages. Run something formulated for a gas engine. Like I said, I recommend Valvoline VR1 but there are other good options out there.

That timing chain is freaking toast! That last bearing you posted doesn't look good either. I wouldn't reinstall that personally. And if one bearing looks like that, I'd plan to check them all. Do your have a local machine shop you can show them to?
 
Button it up and replace the chain, I would not go further into it personally. That chain was really bad, fix it and then decide what to do next after testing it out.
 
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