Engine noise and potential options

Bigmac

Bigmac

Rather be in 29 palms.
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My TJ is making a motor tapping noise. sounds like bottom end and I hear it more clearly on the right side in the fender well.

I'm not an engine expert but im thinking a rod bearing.

It's not one of those horrendous something is broken knocks, its more of a tapping. Ive had plenty of cracked and leaky exhaust manifolds its not an exhaust tick.

First, what does the collective believe the issue is?

I've rebuilt a transmission, couple T cases, and a few other things, but never an engine.

I'd like to tackle an engine sometime, but now isnt a good time. If it is the rod bearings is it possible to pull the pan and do just the bearings? If that's a bad idea, how long can I beat on it without worrying about it tearing itself apart?
 
Bigmac said:
If it is the rod bearings is it possible to pull the pan and do just the bearings?
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You can remove the pan to replace the rod bearing(s), but you would need to do a thorough inspection of the crankshaft and measure using the torque and plastic gauge method.
Probably wouldn't hurt to inspect the piston skirt and cylinder for signs of wear or damage.

Bigmac said:
how long can I beat on it without worrying about it tearing itself apart?
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Difficult to answer that question.
The engine could last a couple days, weeks, months or grenade tomorrow.
IF you can; you should not drive the Jeep until you can afford to rebuild the engine.
 
I first really started to notice or pay attention to it after I replaced the rear main seal last year. I switched from the mobile 1 syn high mileage ive run for years to the " penzoil conventional maybe blended but doesn't say blended" in the yellow jug at that time. Not saying they're related but could be.

after seeing several folks suggest carbon in the top end and sticking valves to be another potential source of their noises I ran some seafoam top end spray through the top end and drove the ever living piss out of it yesterday. Ive got some seafoam bottom end cleaner in as well and am at 80 miles in on the recommended 100-300. Once that's done Ill drain oil and fill with something else to see if that makes a difference.

I know most of that crap is usually snake oil but i felt like at 20 bucks it couldn't hurt to try.

After driving the piss out of it yesterday it started up kind of quiet this morning, went for a drive and came back to the house and the tapping is back to being just as evident as before.
 
I had a on and off rpm matched tapping sound from my "distributor" shaft. cant think of the proper name at the moment (dont have a distributor). I had placed my finger on the Halifax sensor cap and felt the tapping pretty well. noise was strongest on the passenger side and a chunk of cut off garden hose stethoscope'd me right to the area it was emanating from the loudest. new "distributor" assembly and noise was gone. just a simple suggestion of something to look at 🤷‍♂️
 
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Have you checked your timing chain? Sometimes they can get worn or the dampener inside the cover can get worn or out of place. You can definitely pull the pan and check your rod bearings. Pretty straightforward to pull the caps and inspect them, if they’re good wipe them off and lube them up with some assembly lube and toque them back down to spec. 33 ft lbs or 45 nm I believe. Worn bearings will look like they are copper instead of silver

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kincaid.0678 said:
Have you checked your timing chain? Sometimes they can get worn or the dampener inside the cover can get worn or out of place. You can definitely pull the pan and check your rod bearings. Pretty straightforward to pull the caps and inspect them, if they’re good wipe them off and lube them up with some assembly lube and toque them back down to spec. 33 ft lbs or 45 nm I believe. Worn bearings will look like they are copper instead of silver

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thanks for this, I may go that route.Ive done a chain on a previous 4.0 but not this one. If I'm going to pull the pan... and do the chain... that will be easier to pull the radiator out. Ive had the cooling system refresh on my to do list since last year.

If I'm going to go through all that trouble doesn't it make sense to replace the bearings anyway?

what is the plastic torque method mentioned above?
 
CharlesHS said:
You can remove the pan to replace the rod bearing(s), but you would need to do a thorough inspection of the crankshaft and measure using the torque and plastic gauge method.
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could you expound on this? Do I need any special parts or tools?
 
continuing to read on this I see that you can't order bearings until you know what thickness you need. (or something to that effect)

For what it's worth I have good oil pressure. It reads 40 at idle, 20 warm and gets up to 50 on highway. I replaced the sending unit a couple of years ago.
 
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Plastigage is used to check bearing clearances inside engines. You basically take a small snippet the length of the journal and after wiping the oil from the bearing inserts you place it down on the crankshaft and place the cap on. Torque to spec and then remove it and compare it to the measurements on the packaging to see where you are for clearance. Pretty simple but definitely time consuming.

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Bearing inserts will have stamped numbers or letters telling the size. I had to polish mine to see what the rod bearing were. If you don’t have any bad wear and just want to put fresh bearings in shoot for the exact same size that came out.

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kincaid.0678 said:
Bearing inserts will have stamped numbers or letters telling the size. I had to polish mine to see what the rod bearing were. If you don’t have any bad wear and just want to put fresh bearings in shoot for the exact same size that came out.

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thanks for all the good info. Tried a heavier oil and the noise has not changed.

Are bearings directly related to oil pressure? If I have good pressure now, can I ruin it by replacing bearings by whats in the markings?

If I have good pressure not does that necessarily indicate the bearings or not the issue?
 
Could be piston slap. It’s a common issue with these engines. From what I’ve read cam bearings are where the oil pressure is read from so if you replace rod bearings it shouldn’t affect oil pressure.
 
kincaid.0678 said:
Could be piston slap. It’s a common issue with these engines. From what I’ve read cam bearings are where the oil pressure is read from so if you replace rod bearings it shouldn’t affect oil pressure.
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Thanks, I enjoy tearing stuff down and learning how it all works. In the case of engines and differentials though, there are some speciality tools involved... not to mention the cost of the test subject, or downtime with the vehicle.
 
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Everything you need to know about swapping bearings out in your engine is detailed in the FSMs that can be found on this forum for each year. Download the PDF to your phone and you always have a guide for damn near anything on these jeeps
Bigmac said:
Thanks, I enjoy tearing stuff down and learning how it all works. In the case of engines and differentials though, there are some speciality tools involved... not to mention the cost of the test subject, or downtime with the vehicle.
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I just pulled the #6 rod bearings to have a look. Look pretty damn good to me. If this one looks this good should I even bother pulling and checking the rest?

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Bigmac said:
I just pulled the #6 rod bearings to have a look. Look pretty damn good to me. If this one looks this good should I even bother pulling and checking the rest?

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I mean I think the noise would be coming from 1 piston based on the frequency, but I'm considering based on this bearing and the milage of the motor that maybe the noise is coming from something else. Could this be an oil pump noise or something similar?
 
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