jon1998 Posted November 15, 2017 Share Posted November 15, 2017 My 4.0 has developed a knocking sound emanating from the oil pan area, it is very faint at start up and much louder when the jeep is warmed up. It seems to only be present at idle, but when I put it in drive I can hear the knocks slow as the rpm drops. Despite the knock, the jeep has really good oil pressure and runs really good. I pulled the spark plug wires from each cylinder to see if taking the load off would reveal the one with the bad connecting rod bearing, but the noise never went away, suggesting the problem may not be in the connecting rods. I also pulled out all of the pushrods and inspected them for bends; they all looked straight. None of the rocker arms had play in them so I guess the lifters were good. I have also checked the flex plate for cracks and loose bolts and didn't find anything. What could his knock be? Do these engines just make this noise naturally, I have been told rod knock is common to 4.0s, though I haven't personally heard one make a noise like this. Link to comment Share on other sites More sharing options...
yxmj Posted November 15, 2017 Share Posted November 15, 2017 First guess....is it an auto.....cracked flex plate? Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted November 16, 2017 Share Posted November 16, 2017 Or lose torque converter bolts. Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
jon1998 Posted November 16, 2017 Author Share Posted November 16, 2017 It is an automatic, but I did check the flex plate bolts for tightness already and they all seemed fine. I didn't see any cracks either, but are these cracks small enough to be easily missed? How likely is this horrible noise rod knock? Thanks so much for the replies Link to comment Share on other sites More sharing options...
Green Mesa XJ Posted November 16, 2017 Share Posted November 16, 2017 I’ve had the lose bolts on the torque converter it sounds like hell. I’ve listen to a video of a cracked flex plate and it sounds a little worse. But harder to spot the damage . Now there are differ kinds of noises where a lifter is stuck and then the normal 4.0 Diesel-ish sound.Since the sound does not go away with when pulling the spark plug wires I’m going to guess it’s not a rod knocking. Could still be a cracked flexplate. Sent from my iPhone using Tapatalk Pro Link to comment Share on other sites More sharing options...
cruiser54 Posted November 16, 2017 Share Posted November 16, 2017 https://www.cherokeeforum.com/f51/checking-cracked-flexplate-172081/ Link to comment Share on other sites More sharing options...
jon1998 Posted November 16, 2017 Author Share Posted November 16, 2017 I'll check the flexplate again this weekend, sounds like thats what it has to be. Thanks again for the help everyone! Link to comment Share on other sites More sharing options...
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