• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

What is this awful noise?

jk_surgeonfish

NAXJA Forum User
Location
AZ
99XJ with AW4
Changed the exhaust header and after starting up I have this sound that is coming from the bottom of the oil pan.

Video: https://www.youtube.com/watch?v=Ij7eZLK-QMI&feature=youtu.be

I have changed the exhaust header 4 times and am pretty proficient in doing so. Nothing out of the ordinary when I did it this time.

At first I thought... flex plate. Checked the bolts and they are tight. Don't see any cracks either. I ran it with the cover off and the noise does not increase. I would think it would be louder with the flex plate inspection cover removed.

Stuck lifter? I ran some Seafoam in oil for 10 miles and changed oil and filter. No change.

Does it in P, N or D.
Does it when cold or hot.

I can't imagine that I dropped something in the intake port not knowing so when changing the exhaust manifold. I would think the noise would be very loud up top if this were the case. This sounds like it is coming directly below the oil drain plug.

Standing over the engine it is not that noisy as you can hear from the video. Go underneath and it is loud.

When I changed the oil today it was clean with no debris.

Any suggestions as to what this may be? Hoping it is not a piston skirt.:wow:

Thanks!
 
I'm not going to tell you what it sounds like to me.

First I will tell you that it is very difficult to locate the origin of a sound in an environment of steel and concrete. Second, I will tell you to buy a decent mechanics stethoscope and start probing.
 
I'm not going to tell you what it sounds like to me.

First I will tell you that it is very difficult to locate the origin of a sound in an environment of steel and concrete. Second, I will tell you to buy a decent mechanics stethoscope and start probing.

Yes, you are correct hard to tell where the sound could be generated from. I plan on getting a stethoscope today. I have a feeling I will be pulling the oil pan to see some carnage.
 
Email heading your way Jonathan
 
I'm not going to tell you what it sounds like to me.

First I will tell you that it is very difficult to locate the origin of a sound in an environment of steel and concrete. Second, I will tell you to buy a decent mechanics stethoscope and start probing.

Picked up a stethoscope. I should have had one in my toolbox years ago. I like it! I placed above each intake/exhaust on the block and they all sounded the same to me. Placed it on back of block by number 6 and the noise is more prevalent. Toward #1 on top of block can't really hear it well. On transmission can't hear it. Sounds like a diesel tractor when placed on bottom of oil pan.

I probed all over and was not able to pin point one specific location that jumps out and says here I am.

So what did this tell me? I don't think it is from the head by intake/exhaust.
 
Check along the lifter galley, use the distributor/cam sensor to block mounting point as your reference.

For me not being there, it sounds like a connecting rod. Rule out the lifters first.
 
If you can rule out the lifters: With the engine running, pull the plug wire on #6. If the knocking sound changes, drop the pan for a look.
 
Try it with #5?

I pulled all of them and no difference. I took it down to a mechanic I know and they are perplexed. He is a good mechanic. Says that it does not sound like lifters or a piston. He says drive it and if it gets louder then we can look at it again.
 
Years ago, I replaced a clutch for a coworker, on his 2WD XJ. When I was taking everything apart, I noticed the head pipe was loose at the manifold. It was LOUD! After I put everything together, including fixing the exhaust leak, I could hear the bottom end knocking. I told him about it, told him we could not hear the knocking before, because of the exhaust leak. After driving it for a few weeks, he insisted I had done something to his car...

How loud was the exhaust this time around?
 
Years ago, I replaced a clutch for a coworker, on his 2WD XJ. When I was taking everything apart, I noticed the head pipe was loose at the manifold. It was LOUD! After I put everything together, including fixing the exhaust leak, I could hear the bottom end knocking. I told him about it, told him we could not hear the knocking before, because of the exhaust leak. After driving it for a few weeks, he insisted I had done something to his car...

How loud was the exhaust this time around?

Not very loud. This noise would definitely be louder then it.
 
That's way too fast to be a lifter, or even a rod. Having had this problem myself, I'm going to say cracked flex plate. And unfortunately you can't see it until you remove the transmission. I have another theory, but that one is a lot uglier.
 
That's way too fast to be a lifter, or even a rod. Having had this problem myself, I'm going to say cracked flex plate. And unfortunately you can't see it until you remove the transmission. I have another theory, but that one is a lot uglier.

I'm starting to think cracked flex plate as well. If it was a piston I would think it would be very loud at startup and get quieter once warm. This sound is the same hot or cold. Guess I need to bite the bullet and pull the transmission and see.
 
One thing I have noticed driving it today is that in gear it makes the noise. If I keep foot on brake and get RPMs just to 1000 it will go away. Not sure if that helps point to a cracked flex plate or not.
 
I am looking forward to the pictures.
 
Back
Top