Help Diagnosing Engine Knock

[bromel]

I think the Sea Foam is responsible for the metal shavings in the oil, not that rattle you were hearing (which I still maintain is a normal 4.0 lifter noise, though obviously I could be wrong). The point of Sea Foam is to dislodge sludge, which may have been trapping 15 years of shave particles. I would do a few close interval oil changes and see if the particles go away.

 

[SkylinesSuck]

I think the Sea Foam is responsible for the metal shavings in the oil, not that rattle you were hearing (which I still maintain is a normal 4.0 lifter noise, though obviously I could be wrong). The point of Sea Foam is to dislodge sludge, which may have been trapping 15 years of shave particles. I would do a few close interval oil changes and see if the particles go away.

I would say that is super optimistic, but might be worth a shot. Keep in mind though he's already started pulling the pan to take a peak.

 

[The Goblin]

Alright. Got the oil pan down. The problem is, I can’t find anything that is loose! All the connecting rods are Tight, the shaft seems tight. I can’t find anything that has any play in it. The pistons look nice and tight with no play either (from what I can see).

Any recommendations? Do I take off the caps and check the bearings even if they aren’t obviously loose?

Here’s a quick video. (What do you think of the color of the engine?)

Photos

 

[The Goblin]

I think the Sea Foam is responsible for the metal shavings in the oil, not that rattle you were hearing (which I still maintain is a normal 4.0 lifter noise, though obviously I could be wrong). The point of Sea Foam is to dislodge sludge, which may have been trapping 15 years of shave particles. I would do a few close interval oil changes and see if the particles go away.

Oh really? Man that would be awesome if it was the case. I just saw your post after I posted my video. I can’t find anything loose under there. Not in my immediate inspection anyway. I just don’t know if it’s wise to start pulling the bearing caps and checking things if I can’t find anything loose, ya know? A “Don’t fix it if it isn’t broken” type of thing. But I could be wrong.

Would it be good to just change the bearings anyway as preventative maintenance? I’ve seen a video of a guy on YouTube doing just that; it’s just not something I’ve heard of being done (but I’m not a mechanic and wouldn’t have paid attention to it until now, lol).

I would say that is super optimistic, but might be worth a shot. Keep in mind though he's already started pulling the pan to take a peak.

Yeah thanks man. I got it down today. As I said, I’m not finding anything. I guess the noise still could be the flexplate, it’s just that that wouldn’t explain the metal in the oil. But maybe it was just the SeaFoam. What do you think about pulling the caps and inspecting the bearings anyway? Good idea or bad idea?

Would you hear lifter noise from underneath like that? I don’t hear anything from on top, only underneath by the bell housing and back end of the oil pan.

I’ve seen some people talking about adding zinc to the oil and how great that is for these flat tappet lifter engines, and how it really coats the engine surfaces well. What do you guys think about that? I know it may be bad for the cats, but it may be a worthwhile trade off to save an engine.

Or I found this other stuff that claims to be better than zinc and won’t harm the cats (even though it says zinc in the name, the back claims there is no zinc or other metals at all):

 

[SkylinesSuck]

Millions of Jeep 4.0's run regular old oil with no issues. That being said, I have a big cam with high pressure springs, so I run high zddp oil (Valvoline vr1). It's inexpensive insurance anyways. I recommend high zddp oil instead of additive. If you are getting noise from that though, it's too late.

Anywho, you would need to start pulling main and rod caps to check them unless they were super duper screwed up. Do it one at a time and inspect the journals/bearings. Reinstall then move on to the next.

EXTREMELY IMPORTANT--Keep them the same orientation. Do not mix the up. That's why I say do one at a time then reinstall. I scribed arrows and numbers on mine so I can never mix them up.
When you reinstall, make sure you torque to proper spec.

All the bearings should all look smooth and silver'ish. If you see any scoring or copper showing, that's your problem. You can Google examples of spun/scored bearings or journals for examples.

Do you have a torque wrench? If you already had a rear main seal leak, now is the time to fix that. Oil pump is easy to change at this point too if you feel the need.

 

[SkylinesSuck]

Also, zddp = Zinc dithiophosphate. And the brown/gold color is normal varnish. Nothing weird there. Also, do you have a factory service manual? The main girdle will need to come off to get to the main bearings. If all the beatings look good, I personally wouldn't replace them.

 

[The Goblin]

Millions of Jeep 4.0's run regular old oil with no issues. That being said, I have a big cam with high pressure springs, so I run high zddp oil (Valvoline vr1). It's inexpensive insurance anyways. I recommend high zddp oil instead of additive. If you are getting noise from that though, it's too late.

Anywho, you would need to start pulling main and rod caps to check them unless they were super duper screwed up. Do it one at a time and inspect the journals/bearings. Reinstall then move on to the next.

EXTREMELY IMPORTANT--Keep them the same orientation. Do not mix the up. That's why I say do one at a time then reinstall. I scribed arrows and numbers on mine so I can never mix them up.
When you reinstall, make sure you torque to proper spec.

All the bearings should all look smooth and silver'ish. If you see any scoring or copper showing, that's your problem. You can Google examples of spun/scored bearings or journals for examples.

Do you have a torque wrench? If you already had a rear main seal leak, now is the time to fix that. Oil pump is easy to change at this point too if you feel the need.

Hey thanks for the input on the ZDDP. I think I'm going to start using that as well from now on, just in case. As you said, seems like cheap insurance.

Ok, thanks a ton. I was worried that I may mess something up if I started pulling the bearings. I did go ahead and take the girdle off because I knew I would need to do the rear seal, and I went ahead and took the nuts off for the bearing on #6, but I can't for the life of me get the cap off! It is on there so solid that I can't get it to let go. I will keep working at it.

I'm glad I made the right choice to go ahead and take a look at them, thanks for the confirmation on that. I do need to change that main real seal anyway, so I knew I would need to at least pull that last main bearing cap, so I figured I may as well pull at least one of the connecting rod caps as well. I think I will check at least 4,5, and 6. There was no noise at all coming from the front of the engine, even with the stethoscope, so I think I will leave 1,2, and 3 alone.

I do have a torque wrench and I got my hands on a service manual and I found where it has the step-by-step instructions for replacing the bearings, including the torque specs, so I should be good there.

Thanks for explaining the color! I will admit that it freaked me out just a little when I first saw it, even after watching countless videos on YouTube on how to check bearings for knocking! Lol.

Ok, I think I will head back out and see if I can get those caps off. I will do it one at a time like you suggested, thanks for that. I did remember that I need to make sure I keep them all super organized so everything goes back on the way it came off. I'm a little nutty about stuff like that so I should be ok (not a mechanic, so I have some healthy anxiety around stuff like this that helps me keep everything in place! Lol).

 

[SkylinesSuck]

Sounds like you are doing everything right! And those main caps can be a b1tch to get loose. I always whack them from the side with a rubber mallet.

 

[The Goblin]

Sounds like you are doing everything right! And those main caps can be a b1tch to get loose. I always whack them from the side with a rubber mallet.

Thanks!

It seriously just won't budge! Lol. Rubber mallet, here I come!

 

[The Goblin]

Ok, the rubber mallet trick worked! Lol.

so here are a few photos of the top and bottom journals of cylinder 6 (5 looks exactly the same). They look pretty good to me with only slight discoloration. They were all super smooth and the crank journals were as smooth as could be. The weird part is that the bearings actually stuck to the journal when I removed the cap, instead of coming off with the cap itself. They definitely did not fit tight, per se, into the cap or the connecting rod. They just sort sat in them, instead of clicking into them like I expected them too. Also, lots of oil on both sides of the bearings. Aren’t the backs of the bearings supposed to be dry? And only the sides that touch the crank supposed to be oily? Or is that only during installation?

Top bearing, some streaking in the middle (very smooth) some discoloration at the end with the little notch in it:

Connecting rod inside:

bottom bearing:

I’m thinking things look ok. Thoughts?

I haven’t pulled any main journals yet, that will have to wait for another day, I’m tired.

 

[SkylinesSuck]

I dunno about that first pic. Doesn't look great but hard to tell not in person. Streaks mean physical contact and there isn't supposed to be any. Not horrible though? That's certainly not where all the metal came from. How about the rod journal? The journal is the part of the crank the rod bearings and main bearings ride in. They would be the opposing surface to the bearings on the crank.

Was there any metal in the pan? Was the metal you did find magnetic?

 

[The Goblin]

I dunno about that first pic. Doesn't look great but hard to tell not in person. Streaks mean physical contact and there isn't supposed to be any. Not horrible though? That's certainly not where all the metal came from. How about the rod journal? The journal is the part of the crank the rod bearings and main bearings ride in. They would be the opposing surface to the bearings on the crank.

Was there any metal in the pan? Was the metal you did find magnetic?

Hmm. Good point, streaks definitely would mean contact. Everything was super smooth with no gouges or ridges, though. Almost looked more like the varnish on the surface had worn away a little. Both of the upper journals looks this way.

I’m very happy to say that the rod journals looked great. They were super smooth with no apparent streaking or anything. I couldn’t find any scoring at all (thank goodness).

I’m beginning to think I should just replace the bearings anyway since I’m in there, especially if they are a little bit worn.

I didn’t think to see if the metal shavings I found were magnetic. I can go check. I only saw a tiny bit of glitter in the bottom of the pan mixed in with some silt type stuff. But there was quite a bit of junk down there! Almost looked like a bunch of rocks!

 

[Jewellez72]

Hello Goblin, interesting to hear if you fixed your Engine noise(s)? Purchased 2 months ago, I have 2002 TJ 4.0 and it sounds exactly the same as in your Video. Just did an oil change, Oil was black, but found no indication of filings or shiny brass in the Oil. Oil pressure is good and no use of Oil in the last 5000km.

 

[SkylinesSuck]

I just rewatched the video all the way through. I freaked the first time when I saw the "rocks" but you say they crumble apart with no metal, so big relief. That's still crazy looking though! I have never replaced bearings before. I have checked them though. Have you ever used plastgauge?

 

[SkylinesSuck]

The guys over on the Jeep strokers forum would be good to show this stuff to. They are much better versed in engine assembly and diagnoses than I am. Might want to post the bearing pics there. Careful though, you might be building yourself a stroker before you know it

 

[pagrey]

The knock in the video is loud and clear to me. If there is not obvious play in the lower connecting rod bearings I'd move on. Have you checked the wrist pins for obvious wear moving the connecting rods up and down? You should be able to see movement if the bearing was causing that noise.

 

[Jewellez72]

The knock in the video is loud and clear to me. If there is not obvious play in the lower connecting rod bearings I'd move on. Have you checked the wrist pins for obvious wear moving the connecting rods up and down? You should be able to see movement if the bearing was causing that noise.

I have heard a worn Timing chain(High Mileage 250,000km) can make this noise at Idle.......any truth to that?

 

[The Goblin]

Hello Goblin, interesting to hear if you fixed your Engine noise(s)? Purchased 2 months ago, I have 2002 TJ 4.0 and it sounds exactly the same as in your Video. Just did an oil change, Oil was black, but found no indication of filings or shiny brass in the Oil. Oil pressure is good and no use of Oil in the last 5000km.

No sorry, that's what this thread is all about. I'm right in the middle of trying to figure it out. Good luck with yours! If you figure out what your problem is, put it here so people can learn. Thanks!

 

[The Goblin]

I just rewatched the video all the way through. I freaked the first time when I saw the "rocks" but you say they crumble apart with no metal, so big relief. That's still crazy looking though! I have never replaced bearings before. I have checked them though. Have you ever used plastgauge?

Yeah, I totally freaked out too! It seriously looked like the rocks you would put in the bottom of a fish tank! Lol. But they all crumbled so I think it was just carbon deposits that had been broken loose. I went back and looked through it again and saw a tiny bit of the really fine glitter stuff, but that was all. No slivers of metal that I could see. I totally forgot to check with a magnet though.

This bearing stuff is a first for me too! I've never used plastigauge, but I've read a ton about it. The service manual says to use it when installing new bearings, so I may be posting a video of that too!

The guys over on the Jeep strokers forum would be good to show this stuff to. They are much better versed in engine assembly and diagnoses than I am. Might want to post the bearing pics there. Careful though, you might be building yourself a stroker before you know it

Jeep Strokers forum? I may have to head over there and check it out! Thanks for the tip. I will warn them that I really don't want a stroker engine right now... lol. I've got enough on my plate!
I started a thread a while back on the general Jeep forum so I may post the pics there too and see what people say.

The knock in the video is loud and clear to me. If there is not obvious play in the lower connecting rod bearings I'd move on. Have you checked the wrist pins for obvious wear moving the connecting rods up and down? You should be able to see movement if the bearing was causing that noise.

Ok, thanks pagrey. With as loud as the sound is, I would have thought it would be pretty apparent which, if any, bearings are bad. But everything really is tight in there. I can't wiggle or budge anything with my hands. I haven't pulled any main bearing caps yet, so I'm not sure what those look like. I will have to pull at least the rear one because I need to replace the rear main seal, so I will get a better look at it then.

I have heard a worn Timing chain(High Mileage 250,000km) can make this noise at Idle.......any truth to that?

I've heard people mention that as well. Only thing is here the sound is very definitely heard at the rear of the engine and the timing chain is at the front, so I'm guessing that's not my issue. And I've only got 78k on the engine so I'm hoping the chain wouldn't be loose yet! Lol. But in my research, I definitely have run into people referring to a loose timing chain.

 

[pagrey]

I have heard a worn Timing chain(High Mileage 250,000km) can make this noise at Idle.......any truth to that?

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.