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Engine Noise

M

menos

NAXJA Forum User
Location
Moore, OK
I've got a weird/bad noise I'm trying to figure out. To me it sounds like a diesel.
Oil pressure is good. No lower than 20psi at hot idle.
Noise is consistent whether engine is cold or warm.
It does not get louder with RPM, anything over 1500 drowns it out but you can kinda tell it is still there.
Engine is strong with no other problems.

Noise sample

Any ideas?


Specs
--------------
'91 XJ w/146000 miles
4.0 6cyl
AW4
231
 
Sorry I don't have better news, but that is the EXACT same noise mine has made since I got it over a month and a half ago.

I attributed it to lifter noise, but was I ever wrong. Today my motor tossed the #1 rod through the side of the motor.

Upon initial inspection, I discovered that the #1 rod has almost .050" side clearance, -waaay too much. Obviously, this was the noise I've been hearing since day one, -and was very likely the reason the rod fatigued and ultimately failed.

I'm going to start a seperate thread and try to post pictures.

The bad news about what I found is that even if I has discovered the excessive side clearance early on, there would have been little I would have been able to do about it other than a full teardown and a crank kit and rod (at the very minimum).

All I can say is that I'm glad it broke close to home and not up on a trail somewhere.

Wish I had better news, but the noise you hear sounds just like mine did.
 
x2
The sample is kind of muffled but it Sounds like a rod.That or its some horrible piston slap.If it were me I would drop the pan and have a look at the rod clearances...

Oh,
One more possibility,if you have an auto tranny:could be loose torque converter bolts....
 
Last edited:
When you say rod do you mean the rod bearings or something else like the wrist pin? Checking the clearances would involve.... ???

I was hoping this jeep would last me a few years so I hope this is something I can take care of without too much effort. A new long block is really not in my budget right now so I'd like to get it fixed before I end up like ratman572.
 
Last edited:
menos said:
I've got a weird/bad noise I'm trying to figure out. To me it sounds like a diesel.
Oil pressure is good. No lower than 20psi at hot idle.
Noise is consistent whether engine is cold or warm.
It does not get louder with RPM, anything over 1500 drowns it out but you can kinda tell it is still there.
Engine is strong with no other problems.

Noise sample

Any ideas?


Specs
--------------
'91 XJ w/146000 miles
4.0 6cyl
AW4
231
Click to expand...

Really hard to tell for sure from the sound track. Sounds a lot like mine has for the last 2.5 years, 21,000 miles, since I bought mine, but yours sounds a little more like a dull metal to metal thud or knock than mine, I think. Hard to be sure.

Mine is mostly present at cold engine start ups and quites way down after a few minutes of warm up. I also run oil additives like Marvel Mystery oil and Lucas which have nearly eliminated the noise in mine, especially after the first days morning warm up, so I am pretty sure mine is a sticking lifter/loose tappet noise.

I suggest adding some (replace 1 quart of oil with) Marvel Mystery oil, drive it for 10 to 20 miles on the hgihway to see if the noise quites down at ilde. Old 4.0 Jeeps are notoriously noisy and ratman572's blown engine is an rare case from what I have read in this group. If the MM Oil additive has no effect than your problem may be worse.
 
I went out and listened to it again and its hard to tell but it seems like the bulk of the noise is coming from the top end of the motor.
 
X2 on the stethoscope. You can also use a very long screwdriver, with the handle against your ear and put the tip of the screwdriver on various areas of the block etc. Its not as good as the scope.
 
menos said:
I've got a weird/bad noise I'm trying to figure out. To me it sounds like a diesel.
Oil pressure is good. No lower than 20psi at hot idle.
Noise is consistent whether engine is cold or warm.
It does not get louder with RPM, anything over 1500 drowns it out but you can kinda tell it is still there.
Engine is strong with no other problems.

Noise sample

Any ideas?


Specs
--------------
'91 XJ w/146000 miles
4.0 6cyl
AW4
231
Click to expand...

What did you use, (how, what???? details) to record, save transfer and post the sound track? Does the sound track we are hearing sound like the real McCoy, or did it get distorted some.

I have been wondering what the simplest method (hardware, software, operating system.... combo) is for doing this.

If most of us can post clean representative sound clips here for our noisy jeeps it would be major improvement in long distance analysis, diagnostic techniques.

X2 on the Lucas oil, I use the MM oil and Lucas oil both on mine in the summer.
 
I actually used my cell phone's memo recording feature. The sound clip seems to me to be a pretty accurate representation of the noise, although the clip makes it sound a whole lot louder than it actually is.
 
I would not run the engine any more until I dropped the pan and took a look at some rod bearings. If you catch it now, it could save you a ton of $$$.
 
menos said:
I actually used my cell phone's memo recording feature. The sound clip seems to me to be a pretty accurate representation of the noise, although the clip makes it sound a whole lot louder than it actually is.
Click to expand...

Thanks. Then how did you get it from the cell phone to the internet? Do you have that service on your cell phone, or did you transfer it to a PC locally first, if so how?

I can think of several ways I can do it, but non of them are fast and easy on mine end (yet).
 
I can connect my phone to my computer with a usb cable ( I have a windows smartphone). Then I just uploaded the file to the cox ftp server. Cox (my internet provider) give each of their users a little bit of web storage to allow this sort of thing.
 
old_man said:
I would not run the engine any more until I dropped the pan and took a look at some rod bearings. If you catch it now, it could save you a ton of $$$.
Click to expand...

If the rod bearings are scored or otherwise screwed up how likely is it going to be that the crank itself is damaged? If the crank is damaged we are talking about pulling the motor right?
 
menos said:
If the rod bearings are scored or otherwise screwed up how likely is it going to be that the crank itself is damaged? If the crank is damaged we are talking about pulling the motor right?
Click to expand...

Depending on how tight funds are, you can drop the crank from the bottom and take it to a shop and have it ground, then replace it with new correctly sized bearings. If the motor is old and the compression is low, you are going to fight blow by at a later date anyway.

I have taken the crank out, used a leather belt with some jewelers rouge and polished journals that were marginal. I then replaced the crank using .001 undersized bearings. This technique is definately old school, but when dollars don't exist, you do what you have to do.
 
menos said:
I can connect my phone to my computer with a usb cable ( I have a windows smartphone). Then I just uploaded the file to the cox ftp server. Cox (my internet provider) give each of their users a little bit of web storage to allow this sort of thing.
Click to expand...

COOOOL!

Now that I think about it more, I have a 1-800 internet business voicemail line I could call from my cell phone that would do this too. :D Lot easier than looking for and buying a cable and software to attach my cell phone to the PC.

It won't be long before everyone has the web right on their cell phones for this.
 
I'm pulling the pan and I'm gonna take a look at/replace the rod bearings. I'll take pictures and let everybody know what I find.
 
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