Engine Noise questions.

#1
Many of you have heard my 4.0 that sounds like a cummins... Well here is a little history on it, as I'm trying to determine what it may be.

around 75-80k miles it started making some noise at start up, it sounded like a lifter and it has slowly gotten a bit louder and lasted longer.

I have been told it could be a wrist pin, cracked piston skirt, but I was always thinking it was a lifter problem for the longest time.


The jeep does not smoke and doesnt have a noticable loss of power which I would associate with a piston skirt.



This morning I noticed for the first time that when I first fire it up, its actually quiet. And after a minute the noise starts to come on. This seems to be opposite of what it used to do. But I believe its caused by the colder thicker oil.

Can anyone explain this noise based on this information?
 

WolfGT

LIFETIME
SUPPORTER
#4
To determine where the noise is coming from, have you tried the old vacuum hose stethoscope trick? Just put one end of a 3 or 4 foot vacuum hose up to your ear and touch the other end to parts of the engine (valve cover, oil pan, block...). Move it around and you will find pretty accurately where the noise is originating from. If you have two people, it makes it easier because you can step back away from the noise and have the other person move it around.
 
#5
Lifters/valve train. Remember how my Land Rover always sounds like a diesel? I had the valves adjusted by someone who actually knows what they are doing and immediately quieted it down. It sounds like a normal-rural-european-person car now.

So is it only making that noise at startup then gradually goes away? Or ?

Just about anything made by GM makes lifter noises when it is cold. The old blue truck does it, my dad's yukon does it, my mom's old buick did it, and my chevy DD sedan does it. However after warming up it goes away.
 
#6
Lifters/valve train. Remember how my Land Rover always sounds like a diesel? I had the valves adjusted by someone who actually knows what they are doing and immediately quieted it down. It sounds like a normal-rural-european-person car now.

So is it only making that noise at startup then gradually goes away? Or ?

Just about anything made by GM makes lifter noises when it is cold. The old blue truck does it, my dad's yukon does it, my mom's old buick did it, and my chevy DD sedan does it. However after warming up it goes away.
mine used to go away, now its all the time.
 
#7
To determine where the noise is coming from, have you tried the old vacuum hose stethoscope trick? Just put one end of a 3 or 4 foot vacuum hose up to your ear and touch the other end to parts of the engine (valve cover, oil pan, block...). Move it around and you will find pretty accurately where the noise is originating from. If you have two people, it makes it easier because you can step back away from the noise and have the other person move it around.
I need to get somebody to do this with me.
 
#8
Your hydraulic lifters might be the issue. I know valve adjustment on my engine got rid of the noise but with hydraulic lifters it auto adjusts itself. The auto-adjustment-part of it sounds shot.

Unfortunately I don't know anything about hydro lifters so that is all I got.
 
#9
I have a trick fix, but it's not fun.
Valve spring shims!
My buddy has had great success using shims. It's the springs that get weak over time. There are several other possibilities, but I know for sure this has done the trick 4-5 times recently.
 
#10
Did a little more checking on it this weekend. The My knocking is not there when I first crank it for about 30 seconds while the oil pressure is building. Then it is the loudest for about 30 seconds, then it quites down some.
 

WolfGT

LIFETIME
SUPPORTER
#11
Sounds like there is a little animal in there. It takes him a few seconds to wake up and he starts pounding trying to get you to shut off that loud noise, then he gets tired.
 
#16
Yeah, I'm fairly certain mine is something in the top end now. But I plan to put it on the stand and stroke it after I figure Out whats wrong with it.
 
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