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4.0 engine knock

Airjunky

TJ Enthusiast
Dec 13, 2018
172
Liberty Lake WA
Driving home from work on Thursday and the engine started developing a knock. Initially it sounded like it was low on oil, idled fine but sounded like valves when the engine got over 2500 or 3000 RPMs. Oil pressure was good, around 40 psi. I pulled over & checked the oil, no leaks, and was full. In the next few miles, the noise changed to a loud ticking. This weekend I pulled the valve cover and found the rockers & push rods were good, overall looked really good. I drained the oil and opened up the filter..... nothing very clean, no chunks. I did a compression test and compression came in from 120 - 140 psi..... #3 & 4 being the lower psi. Listening to it, it seems like it's coming from the front of the engine, maybe a timing chain tensioner?
Been doing a bunch of reading and listening to videos. Whether it be a timing chain, wrist pin, broken piston skirt, or whatever, it sounds like it's new engine time.
Dammit.
 

Nimbley

TJ Enthusiast
Jun 21, 2018
131
Somewhere in the desert
Roll the engine over a little and watch the lifters. Intake valve will close before TDC. Exhaust valve will open after TDC. Generally a lower end knock will be a lower frequency and a top end noise will be a higher frequency. Think bass versus treble. In the video it kinda sounds like a collapsed lifter.
 

Medali

TJ Enthusiast
May 11, 2018
116
Tunis, Tunisia
Sorry to tell you, but it's exactly the same sound I heard one day before my engine creaked and broke ... In the end it was a broken piston due to the connecting rod that no more turns around its axis ... It was probably due to a problem with engine oil ...

Envoyé de mon MHA-L29 en utilisant Tapatalk
 
OP
Airjunky

Airjunky

TJ Enthusiast
Dec 13, 2018
172
Liberty Lake WA
Sorry to tell you, but it's exactly the same sound I heard one day before my engine creaked and broke ... In the end it was a broken piston due to the connecting rod that no more turns around its axis ... It was probably due to a problem with engine oil ...

Envoyé de mon MHA-L29 en utilisant Tapatalk
I parked the Jeep a week or so ago. Hoping to pull the exhaust and oil pan to see what happened. Bought an engine stand from a neighbor. Need to get off my ass and get to dismantling the damn thing.
 
OP
Airjunky

Airjunky

TJ Enthusiast
Dec 13, 2018
172
Liberty Lake WA
Got on the Jeep this morning and drained the oil, removed the exhaust, oil pan, starter and battery. Nothing glaringly obviously wrong, other than the wood screw in the bottom hole of the scatter shield & the loose bolts on the exhaust manifold/header. Still no chunks in the oil pan. And couldn't find anything bent or broken.
 

astjp2

TJ Addict
Aug 22, 2018
1,661
Utah and Alaska
With the pan off, look up at the cam lobes, roll the enigne over BY HAND with a ratchet and socket on the crank pulley large bolt, if you have a wiped lobe, you will see it because it will be round instead of egg shaped. if not you can check the lifters, they do collapse and not hold pressure causing a click. rock the crank back and forth and watch each rod, you may see excessive play in the rod to crank position.
 
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