Help Diagnosing Engine Knock

nsiciliano2 said:
Alright Gents, here’s my update with everything I’ve done so far. My “ticking” sound just recently turned into a loud knocking sound so that’s what made me investigate further.

I removed my valve cover to find the rockers and push rods loose on cylinder 3. All the others were tight and had no play. So I played it safe and replaced all of the rockers and push rods. Sealed it back up and still had the same loud knocking sound.

Next I dropped the oil pan🤦‍♂️... To find crank shaft bearings 1-6 worn and loose, timing chain loose as hell, and the skirt on piston 2 broken (which is where my loud knocking sound was coming from I’m assuming). So as of now I gotta check to see if cylinder 2 is scored or damaged badly. If it’s not I’ll start putting it back together here over the next couple of weeks.

As of now I’m assuming my ticking sound came from the loose timing chain. However I know that has been replaced by various people on this thread and has still left them with a ticking sound.. with that said I’m still worried about a possible lifter issue... attached are pictures and a video of the timing chain.

Lmk if you have trouble viewing the images.

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Was the knocking during cold start only or did it remain even after reaching operating temperature? To help distinguish it apart from other knocking we've been talking about.

Sorry to see that happen.
 
Harcust said:
Not much to update on from my end. The Jeep is street legal so I'm finally putting some miles on it. Right now it has 5 quarts of 10w30 and 1 quart of Marvel Mystery Oil with a Mopar filter. I recently ran a bottle of Valve Medic in there to try and help clean the valvetrain for a hopefully easy fix. This stuff has diesel, kerosene and some other chemicals in it.

So far it really sounds like (insert placebo affect) it's quited the valvetrain while driving. I could really hear some noise upwards around 3k+ RPM and it seems to have quieted that pretty well. It's done absolutely nothing for the cold start knock.

For now I plan on just driving it and doing some oil flushes. The timing chain came in but I'm going to wait to install it at a later time.

On a side note I tried using a rubber hose for a stethoscope to trace the noise location and I really can't find it.

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Hmm. Haven't seen that stuff mentioned yet. Keep us posted if things get better over the next little while, hopefully that clears it up for you!

Good luck with the timing chain, whenever you get around to it. It was definitely a job, but being that I'm not all that educated in mechanics, it really wasn't that bad. I mentioned this before, but if you want to change the chain without removing the radiator, the pulley removal tool that Harbor Freight sells is awesome since it has a shorter main bolt. The ones you can rent from the autocrats stores all have a long bolt and are therefore unusable unless you take the radiator out (I really didn't want to do that!).
 
The Goblin said:
Hey everyone! I am brand new to your forum here and pretty new to the Jeep world overall (just a few months). I picked up my 2002 TJ 4.0L automatic earlier this year and have spent quite a bit of money and time working on it. It only has just over 78,000 miles.

The engine had a ticking noise from the front/top of the engine when I bought it, but after treating the oil with Sea Foam, changing the oil and adding Lucas, changing the alternator and serpentine belt, the ticking went away.

BUT, after clearing up that ticking, I was able to hear a new noise that I couldn't hear before: a knocking coming from underneath the engine. It sounds like it is coming from the back of the oil pan/flex plate area. I have done a ton of research online and posted some things over on Jeep Forum, but I wanted to post here to see if my fellow TJ owners would have some more specific thoughts. I've read a ton of posts, many here, but I'm still not confident on what this sound could be.

Various shops have looked at it while doing other things for me (changing gears, assessing a transmission problem I'm working on) and they all seem to have different opinions like piston slap, main bearings, rod bearings.

The sound is not there when I first turn on the engine, but it shows up after about 60 seconds. It goes away when the engine is under load or when the RPMs get up to normal driving range. The oil pressure seems to stay constant.

If it was a main bearing or rod bearing, wouldn't the oil pressure be low?

I have checked, removed, and re-installed the torque-converter bolts and that didn't change things.

I'm really leaning towards a cracked flex-plate, but for some reason these shops I've been to don't seem to think that's it. I've watched a ton of videos on youtube about rod knock and they all seem to be very loud and audible from the top of the engine; mine you can't even hardly hear unless you stick your head underneath the Jeep (where it's pretty noticeable). I found a series of videos from a guy with an older Cherokee and the sound in his video I swear sounds a lot like mine and he ended up changing his flex plate.

I did notice a possible exhaust leak when I was looking around with a flashlight under the engine. Looks like it was just above the cats.

So, any advice guys? Any way to rule out bearing knocks or flex plate issues? Could it actually be an exhaust leak? Anyone else experience this?

This is it:
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I’m glad I found this. My Jeep make the same exact noise just not quite so loud and it’s not always there.
 
SkylinesSuck said:
Lucas in the oil? That might be the problem right there lol. That is (mostly) in jest. I would avoid that junk in the future. It could certainly cause a lifter to tick. Seeing as how all of this started when you changed your oil, it seems like a possibility. I said change your oil because I would look for sparkly bits floating in it. That would tell you if you have a serious engine issue (like a spun bearing). The later oil pressure gauges like yours are just glorified idiot lights that show in the middle or not. Early gauges are functional but watching it fluctuate with RPMs freaks some people out so Jeep removed it. Or so the story goes.
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Yea o have a 97 at idle the pressure drops low ish and sometimes it’s at 40. When not at idle it’s almost always at 40. I replaced the sending unit and it’s better but I’m just going to let it do it’s thing
 
Jackjack97 said:
Yea o have a 97 at idle the pressure drops low ish and sometimes it’s at 40. When not at idle it’s almost always at 40. I replaced the sending unit and it’s better but I’m just going to let it do it’s thing
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Hey! Welcome to the group! Glad you found us.

What engine have you got? 40PSI is just fine for the 4.0 engines. The rule of thumb is 10PSI per 1000RPMs. How low is it going?
 
The Goblin said:
Hey! Welcome to the group! Glad you found us.

What engine have you got? 40PSI is just fine for the 4.0 engines. The rule of thumb is 10PSI per 1000RPMs. How low is it going?
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Yes I have the 4.0 and when the motor is cold and when driving it is consistently at 40 psi but after warming up the jeep idles around here

i have the same noise you are having but not nearly as loud and no metal in the oil pan.

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Jackjack97 said:
Yes I have the 4.0 and when the motor is cold and when driving it is consistently at 40 psi but after warming up the jeep idles around here

i have the same noise you are having but not nearly as loud and no metal in the oil pan.
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Looks a little low according to the gauge, but the oil pressure sending units are notoriously unreliable. I'd pick up a mechanical gauge from Harbor Freight to confirm, or just replace the sender. If you have low oil pressure, you'll generally hear it in the top end.
 
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bromel said:
Looks a little low according to the gauge, but the oil pressure sending units are notoriously unreliable. I'd pick up a mechanical gauge from Harbor Freight to confirm, or just replace the sender. If you have low oil pressure, you'll generally hear it in the top end.
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How do you swap to a mechanical gauge?
 
Jackjack97 said:
Oh so I won’t see the oil pressure at the gauge in the cluster?
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No, not while the mechanical gauge is connected. It's just a temporary measure to see what the actual oil pressure is. You don't want to drive around with the mechanical gauge flopping around in the engine bay. Assuming you're at 13PSI+ at hot idle, you're good to go and you can buy this:

https://www.amazon.com/dp/B00MJ2E04E/?tag=wranglerorg-20
 
bromel said:
Looks a little low according to the gauge, but the oil pressure sending units are notoriously unreliable. I'd pick up a mechanical gauge from Harbor Freight to confirm, or just replace the sender. If you have low oil pressure, you'll generally hear it in the top end.
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And which gauge do I need
 
Jumping in the frey here with you Amigos! Got my 99, five speed, 128k, in July 2019, and have basically been replacing everything I can, non-stop since then. I have read this entire thread, mine runs great, shifts great, oil pressure great, And sounds exactly like all of these TJs on here. Driving me crazy because I'm very particular.
My theory is perhaps this, the previous owner, had a local mechanic shop, (non jeep guys), install a new clutch, flywheel, and transmission mount on it. AX-15 transmission. In my research, I've found out that these clutch fork springs wear, break, fall off, and cause a rattle, or knock, like mine. Supposedly doesn't hurt anything, but sounds bad.
And most mechanics, not knowledgeable with these, either dont see it, if its fallen out in small pieces, or don't replace it, for one reason or another. So, big rattle.
I removed the slave cylinder, and can actually reach into the bell housing and grasp that end of clutch fork, and move it fore and aft, telling me it is not clamped to the pivot ball on the other end. So I have a small inspection camera that hooks to my android phone on the way, (ebay, $12,lol), and will definitely be able to remove the slave cylinder, camera it, and see.
just thought I'd add to this thread, maybe this is it on some of our rigs.
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Hello, Samwise! Welcome to the frey.

Interesting idea. I have the NV3550 but when checking my service manual it shows the exact breakdown picture you posted. If this spring were the case, do you think it's the loose fork making the rattle or the spring? I'd imagine if the fork was loose and rattling depressing the clutch pedal would put pressure on the fork and stop the rattling. I have a borescope and could possibly take a look at mine tonight.

You've said that you've replaced a lot of stuff, what all have you replaced? I've been too busy on my house to work on my TJ but I plan on investigating it more soon, hopefully. I drive it daily and it hasn't gotten better nor worse, yet.

Edit: I forgot to add that the owner I purchased it from said the clutch was changed when they changed the engine. So that may be evidence towards a problem in that area.
 
Harcust said:
Hello, Samwise! Welcome to the frey.

Interesting idea. I have the NV3550 but when checking my service manual it shows the exact breakdown picture you posted. If this spring were the case, do you think it's the loose fork making the rattle or the spring? I'd imagine if the fork was loose and rattling depressing the clutch pedal would put pressure on the fork and stop the rattling. I have a borescope and could possibly take a look at mine tonight.

You've said that you've replaced a lot of stuff, what all have you replaced? I've been too busy on my house to work on my TJ but I plan on investigating it more soon, hopefully. I drive it daily and it hasn't gotten better nor worse, yet.

Edit: I forgot to add that the owner I purchased it from said the clutch was changed when they changed the engine. So that may be evidence towards a problem in that area.
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Hey, sorry, got busy, didn't mean to take so long,
I have replaced almost everything maintenance wise, All brake parts, all fluid, filters, hoses, bulbs, Mopar thermostat housing, thermostat, water pump. All U-joints, hub unit bearings, every tie rod end, upper lower ball joints, and complete ZJ tie rod end conversion.
MY TJ, when idling, sounds just like the videos posted in this thread. like a little diesel. once warm, little less so.
When taking off, especially from first to second, when clutch is engaged, under load, Rattle tick knock.
Jeep runs like a scalded dog, Shifts great, tons of power, oil pressure great, temps great. doesn't smoke, doesn't leak, doesn't burn any oil at all.
Today, pulling a treacherous, curvy, steep mountain road, ( VERY steep), in first and second, sounds about like a diesel. Loud.
The longer this goes on, the more I'm convinced its the clutch fork rattling. IDK.
 
Update. I finally got to do some work to the Jeep today. My goal has been to replace the rear main seal and oil pump.

Recently I took the Jeep on it's longest trip yet and got the engine nice and heat soaked. I stopped at a store and when I started back up I had a check guages light come on but only for literally a second or two. I assumed it was oil pressure but it happened so fast I didn't see which guage it was. I put a mechanical guage on it and it's matching what my cluster says, about 20 to 20 psi at idle, hot. I understand this is acceptable and the PCM needs to see 4 psi or less to trigger a light for oil pressure but I decided for $80 I'll just throw a pump on it while I had the pan off. I also tried cleaning the oil galley where the pressure switch is and it was fine.

Anyways, got the exhaust off fairly easily and the pan also but ran into some unexpected wear. The cam lobes are pretty nasty looking and pitted up. The engine is a junkyard swap engine with unknown miles.

The timing chain is also very sloppy but at this point I maybe looking at a cam swap or I may throw it together and drive it into the ground and swap the engine.

What do you guys think?

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SamwiseGamJeep said:
Jumping in the frey here with you Amigos! Got my 99, five speed, 128k, in July 2019, and have basically been replacing everything I can, non-stop since then. I have read this entire thread, mine runs great, shifts great, oil pressure great, And sounds exactly like all of these TJs on here. Driving me crazy because I'm very particular.
My theory is perhaps this, the previous owner, had a local mechanic shop, (non jeep guys), install a new clutch, flywheel, and transmission mount on it. AX-15 transmission. In my research, I've found out that these clutch fork springs wear, break, fall off, and cause a rattle, or knock, like mine. Supposedly doesn't hurt anything, but sounds bad.
And most mechanics, not knowledgeable with these, either dont see it, if its fallen out in small pieces, or don't replace it, for one reason or another. So, big rattle.
I removed the slave cylinder, and can actually reach into the bell housing and grasp that end of clutch fork, and move it fore and aft, telling me it is not clamped to the pivot ball on the other end. So I have a small inspection camera that hooks to my android phone on the way, (ebay, $12,lol), and will definitely be able to remove the slave cylinder, camera it, and see.
just thought I'd add to this thread, maybe this is it on some of our rigs.
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@AndyG
 
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Ruh roh. I haven't reread the rest of this thread, but that looks like some bearing wear. Can you catch any of those marks with your nail?
 
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