engine knock can't locate

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bkruger

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OK so i'm having an issue finding a knocking sound with my 2004 Liberty renegade. i've done a compression test and all 6 cylinders are fine. i later read that it could be rockers, lifters, and or a fallen valve..... hence i've taken this thing all about and none of the above i've mentioned is bad. i get plenty of oil coming up to the valve train , all 12 lifters are working and can be squeezed and looking at the location of the springs and valves i see none that have dropped. oh and also not one rocker was off. so please someone let me know where to go from here. thanks in advance
 

TwoBobsKJ

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OK so i'm having an issue finding a knocking sound with my 2004 Liberty renegade. i've done a compression test and all 6 cylinders are fine. i later read that it could be rockers, lifters, and or a fallen valve..... hence i've taken this thing all about and none of the above i've mentioned is bad. i get plenty of oil coming up to the valve train , all 12 lifters are working and can be squeezed and looking at the location of the springs and valves i see none that have dropped. oh and also not one rocker was off. so please someone let me know where to go from here. thanks in advance

You've been pretty thorough going through the top end so my guess would be a bearing on the bottom end. This is what mine sounded like when I finally tore it down and swapped in a new 3.7:

Bad bearing sound

Bob
 

mkarns02

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Is it a consistent knock or just at low rpms?

I have a knock only heard at low rpms.

Engine runs great and there are no other problems.....

My mechanic says to ignore it until/unless it gets worse.

It still bothers me!
 

libertybob

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Engine knocks...

Engine knocks can come from bearings but these usually go from bad to worse quickly. A knock can also be from the wrist pins in the pistons or piston slap in a worn engine. These are more subtle and can come and go depending on engine temperature. An experienced mechanic can usually tell the difference between bearings and piston related knocks. Your mechanic is correct that until it gets worse, diagnosis is difficult.
 

MarkJ

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You can pull coil wires off one at a time to depower each cylinder. This sometimes helps isolate it to a particular cylinder if it is piston, wrist pin or rod related.
 

dougmac

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When I suspect a rod knock, I take the oil filter off and cut it apart. I then inspect the media for bearing material. I use tin snips to cut the housing so I don't introduce metal into the filter when I open it up.

It never fails me.... bad bearings make metal flakes every time....
 

WestAussieKJ

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I have just been through this on my 3.7.It was making this solid thonk type noise at high idle and would come and go and low idle. It appeared to be coming from the left side in the cam cover and down low in the block. I pulled the engine when I took the oil pan off No1 Big end was dark brown /black where all the others were light brown. It had chewed the big end bearing out and worn the crank journal about 2 mm undersize. dougmac's suggestion of cutting open the oil filter will show up a bearing as the oil from mine looked like iridescent paint and the oil pan was full off metal flakes. I definitely would not leave as mine had run too long and the crankshaft and conrod were unrepairable. Though fortunately a local engine shop had a reground crank and conrod for $450 Aussie dollars which I thought was pretty good
 

libertybob

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Knock..

Check the axial play of your crankshaft. I had a manual transmission that had worn the engine thrust bearing from too heavy a pressure plate. The worn away thrust race allowed the crankshaft to move enough axially for a rod to hit the engine block intermittently causing the knock to come and go. This is rare but one more thing to check. I could move my crank about 0.100" back and forth by grabbing the harmonic balancer. The engine was scrap due to the wear on the thrust race seat.
 
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Hockeygoon

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See my post about metal in oil. If you are not seeing metal when you change the oil you might try these guys:

Blackstone Labs


Most likely it is a rod bearing (or all the bearings) - after some research I've found this very basic part of the engine has proven too difficult for the engineers at Dodge.
 

Birdman330

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See my post about metal in oil. If you are not seeing metal when you change the oil you might try these guys:

Blackstone Labs


Most likely it is a rod bearing (or all the bearings) - after some research I've found this very basic part of the engine has proven too difficult for the engineers at Dodge.

Well, they did try to build an engine including testing it in VR Cad Simulations IE the 2.7L V6 and look what happened with that. So doesn't surprise me something like this would happen despite the 3.7L being an nice firm engine in my opinion.
 

Glen_S

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I hear a slight knock in my 04 when first started up, but it seems to go away completely after 5-10 minutes or so. I just attributed it to a noisy lifter that seems to quiet down once warmed up.

Anyone else run into this on their V6?
 

southernwake

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I have a slight knock when the engine is cold or cooled off from driving. I changed the oil Saturday and drove it around town and took it on a quick 50 mile round trip that evening, No noise, it sat all day Sunday. Monday I fired her up and heard the slight knock sound. I drove it to work conservatively and when I got there no more knock. When she warms up the knock goes away. Its not the right sound for a lifter tick or top end tapping noising. Wondering if maybe its just a wrist pin. with 137k on the clock I would hope it isn't a rod bearing, would be a little disappointed. I have put the last 20k on her and have been very thorough about changing the oil at the right times and using the right oil and all other maintenance.
 

TwoBobsKJ

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I have a slight knock when the engine is cold or cooled off from driving. I changed the oil Saturday and drove it around town and took it on a quick 50 mile round trip that evening, No noise, it sat all day Sunday. Monday I fired her up and heard the slight knock sound. I drove it to work conservatively and when I got there no more knock. When she warms up the knock goes away. Its not the right sound for a lifter tick or top end tapping noising. Wondering if maybe its just a wrist pin. with 137k on the clock I would hope it isn't a rod bearing, would be a little disappointed. I have put the last 20k on her and have been very thorough about changing the oil at the right times and using the right oil and all other maintenance.

Listen to the sound in the video I posted in the engine swap overview in the How-To section. Obviously the engine is apart but when I grabbed the rod and moved it around it had the same sound characteristics as when the engine was running.

I hope your sound and the one I had aren't the same :blah:

Bob
 

southernwake

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TwoBobs, I listened to that yesterday and read through that and a couple other threads about the engine knocks.

I doesnt sound quite the same. What is throwing me off is the fact that it just goes away when the engine is warmed up . And it just started after an oil change. I filled the oil back up and even let it sit for 15-20 minutes because I was replacing the air filter and cleaned up all my tools and everything before checking then level.

I have already started pricing replacement engines just in case it gets worse I have an idea of what i am looking at.
 

Logan Savage

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A couple years ago I changed the oil in a vehicle I have & I noticed a noise like bearing rattle on first start up . I also noticed it was taking longer for the oil light to go out when first starting . I changed the filter again & no more problems . I'm convinced I got a bad filter . Since your noise started right after an oil change , if I was you I'd change the filter again .
 

teeje

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Wrist pin would sound like a loud tick not a knock. Your problem is elsewhere. Post a video of it if you can.
I had a brand new engine installed and it had a bad wrist pin. Would've fooled you to think it was a lifter.


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ltd02

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TwoBobs, I listened to that yesterday and read through that and a couple other threads about the engine knocks.

I doesnt sound quite the same. What is throwing me off is the fact that it just goes away when the engine is warmed up . And it just started after an oil change. I filled the oil back up and even let it sit for 15-20 minutes because I was replacing the air filter and cleaned up all my tools and everything before checking then level.

I have already started pricing replacement engines just in case it gets worse I have an idea of what i am looking at.

Mine would only knock when cold. Not a loud knock and completely gone when warm. It was definitely low end for mine. Did it for a few years. Couple weeks ago I spun a bearing. Partially "locked" but still runs, well, ran. It's partially dissected in my garage. I hope to get a better look at things if I get it out of the KJ this weekend (if all goes well).
 

teeje

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Take a video under the jeep would help more. Almost sounds like something else


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