03 jeep liberty 3.7 engine problems

[03jeeprenegade]

i have a 03 jeep liberty with the 3.7 v6 and a 116000 miles couple hundred miles ago i noticed a knocking when i would get the motor above 2500rpm.was fine for a while then i took a 5 hours trip going 75 and by time i got there it was knocking at idle and pretty bad when im hit the gas.
so when i got there i started it up and sound like its coming from the right side cylinder head, so i pulled the valve cover to inspect the rockers and spring and everything looks good. so one guys was telling me a way to test if its the rod bearings bad by pulling one spark plug wire at a time and starting it up and if the knocking goes away with one of the plugs disconnected then its the rod bearing. well i did that and the knocking didnt go away, but my question is when i do that should i have pulled the spark plug??? and i was told to do a compression test to see if any of the valves were bad. did that and all 6 had 150psi. looking at the harmonic balancer it looks good is there any way to check if the HB is bad??.
any help would be great, im kinda stuck if the tests i did are rite its has to be the harmonic balancer rite?

 

[streetglideok]

The idea of killing spark to a cylinder to identify rod knock goes back to the thought process that when the piston isn't getting hit with an ignited charge, it won't transfer that sudden surge of power to the worn rod bearing, and it will stop knocking. Doesn't always work that way however. In reality, they can knock anytime they are spinning, but they may be more pronounced with ignition in that cylinder. A stethoscope may help pin down the general area the noise is coming from. Regardless, an engine knock from the lower end of the engine means the same thing no matter what rod it is, the engine is going to need replacement or torn down.

 

[CactusJacked]

A sound coming from the cylinder head isn't lower engine. Noisy lifters, and rod knock or piston slap have distinctly different sounds. Lifters sound like a clack, lower engine noise is more of a muffled knock sound. A video with good sound may help here.

 

[03jeeprenegade]

https://www.youtube.com/watch?v=QhRcVBwgX7w&feature=youtube_gdata_player
I don't have a video of my jeep yet but this video sounds exactly like mine minus the squeal noise.

 

[TwoBobsKJ]

This is what a bad rod bearing sounds like. Obviously the sound wasn't the same when the engine was running as it is here, but this may help you determine if the noise is a bearing or other component. Click the picture to start the video.

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Bob

 

[CactusJacked]

Sure has that rod knock/dry bearing scraping sound to me.

 

[03jeeprenegade]

ya thats what i was thinking, but was just hoping it was the harmonic balancer. but from the looks of it the harmonic balancer it is fine. so i guess ill just have to drop the oil pan and check the rod bearings!! i know you cant really tell by ear but ive had a rob bearing go out in a old ford i had and sounded completely different. the jeep really sounds like its coming from the top end but sounds like a rod bearing. thats what was making me think is was a bad HB.
any advice where i should go from here would be great!!!!!!!!!!!

 

[03jeeprenegade]

another thing i noticed is when its running and knocking i can hear the knocking standing at the back of the jeep through the exhaust, kinda sounds like a ping through the tail pipe, a bad rod bearing wouldn't do that would it??

 

[CactusJacked]

Not unless the rod let loose and you're running on only 5 cylinders. Or, could have sucked/dropped a valve. I know you checked under the passenger side valve cover, thinking that's where the sound is coming from, but what about looking at the drivers side? Even though things in the valve train appear to be moving as it should, you could have dropped a valve seat. Pistons and heads don't really like having extra metal parts getting slammed around in there. If it's valve related though, that scraping noise throws me then. Unless that started a chain reaction of catastrophes. A compression test may help pinpoint the offending cylinder, but I think you're looking at a teardown/replacement regardless though. Does it sound at all like there may be an external noise? You could remove the serpentine belt and run it to see if the engine sounds any different. Another thing to look at is check to make sure none of the torque converter bolts came loose and are hitting the block, or that the flexplate isn't cracked. It's a long shot, but worth a look.

 

[TwoBobsKJ]

ya thats what i was thinking, but was just hoping it was the harmonic balancer. but from the looks of it the harmonic balancer it is fine. so i guess ill just have to drop the oil pan and check the rod bearings!! i know you cant really tell by ear but ive had a rob bearing go out in a old ford i had and sounded completely different. the jeep really sounds like its coming from the top end but sounds like a rod bearing. thats what was making me think is was a bad HB.
any advice where i should go from here would be great!!!!!!!!!!!

Unless you have a 2WD getting the oil pan off is a MAJOR project - and even if you get it off you'll have to deal with the windage tray which blocks the crankshaft/rod bearings. Here's what it looks like:

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You may be at the point where you wait for the engine to give up the ghost then swap in a replacement. Here's a summary of how to do it.

Bob

 

[profdlp]

Holy cow - that looks like there was an earthquake at the parts warehouse in there. :icon_neutral:

 

[03jeeprenegade]

well i ended up pulling the motor and pulled the oil pan and one of the rod bearing where almost completely gone. everything else looks great, now i found a place that sells rebuilt crankshafts that come with rod and main bearings. but it looks like the connecting rod may have been damaged is it ok to replace just one rod and does anyone know where i could get one. i dont have the money to get a rebuilt motor any advice would be great and i will put up pictures later.

 

[CactusJacked]

Guess that came as not much of a surprise to you. Do you have a machine shop in your area? Depending on how bad, or not, the rod is, a machinist can grind down the ends where the cap meets the rod, which closes the hole opening down. Then machines the opening round again, and back to factory specs, removing the scored/gouged surface.

 

[TwoBobsKJ]

Holy cow - that looks like there was an earthquake at the parts warehouse in there. :icon_neutral:

Ha! :gr_grin:

Yea, the garage was rather filled - each corner had a collection of components from different parts of the engine/engine bay.

'In this corner, weighing just under 72 pounds. we have the cooling system. And in this corner, we have the reigning king of suck, the intake manifold...' :happy175:

Wife had to park in the driveway - and it was winter. And she wasn't happy. But did my part and brushed the snow and ice off before she headed out in the morning :icon_lol:

Bob