98 4.0L

I noticed this 2 days ago, I have attacked the engine with a stethoscope not really keying in on the exact location. Has anyone heard this before? This may sound weird but it actually has the beat of a cat purring. Comes and goes but very fast like, thats the best way i can explain it, you can hear it in the video. I have a free Saturday coming up without the kids so I would like to know where you would start. Thanks

 

Starting with #1 spark plug, pull each plug wire, in turn, to see if the noise diminshes or goes away. The cylinder with the plug wire disconnected that has an affect is the bad boy.

Sounds like a piston pin (?). #1 is known for this.

 

Ill 2nd that sounds lika piston pin tapping....mine has a similar sound but goes away after its warmed up and been like this for a long long while....how many miles u have on it

 

I was hoping y'all wouldn't say that. It has 170k on it. Is that the only way to diagnose it?

 

Does it stop after it warms up?

 

No. You can tear the engine down and take a look.

 

This is my daily driver so if I can change a bearing by removing the oil pan instead of removing the motor, that would be the best route

I just disco'd all the spark plug wires one by one and the sound did not diminish one bit.

 

It does not go away once it warms up

 

What weight oil you using?

 

10-30

 

I am gonna say unfortunately it might be that time

Try a thicker weight oil maybe until it craps out on you lol

 

Run it till it blows!!! Put 5 quarts of oil and a quart of Lucas! It will run forever lol!!

 

I see what your saying and thanks for the input, but there has to be one specific component causing this issue. If its pistons I would pull the motor. If its something with the bottom end, I could possibly pull the oil pan and fix it there. I will add the Lucas, what other steps of troubleshooting would you recommend? Thanks again

 

What's your oil pressure at? You sure you need Lucas?

 

Start breaking her down and see what you see....take many many pics as to I am curious myself