Hey there! Still new to the forum so my searching abilities aren't all that great yet. Anyway I have a 2000 xj with 177k on the odo. (though maybe someone can help with this other question)... the title to my jeep says 2000, but when i went to auto zone to have a cel read (said bad 02 sensor) their computer system said my car should have 6 02 sensors? climb under the car and I only have 2.. so we went back a year in the computer system to a 99, low and behold that model year only has 2 sensors. so is my jeep really just a 99? and correct me if I'm wrong but the 99's were when they started the 0331 head right?

anyway sorry for the rant^^ back to why I posted.

I did some searching and came across this thread https://www.cherokeeforum.com/f2/ano...estion-120231/ the op had a similar noise in his motor to what I'm hearing in mine.

I just started to notice the knock in the motor maybe two days ago and the sound has stayed very similar. I first noticed it when starting the jeep, my car will usually fire right up but it was having some hard startups. Initially I was thinking maybe my crankshaft position sensor was talking a dump. But then I noticed the knocking noise.

Right when you first start the motor (and this happens whether hot or cold) i can hear a very loud audible knock, sort of a hollow knocking sound.. It will make roughly 5-7 knocks then stop. So I had assumed maybe I need some oil, that the lifters were dry on top. added some oil to the car. the issue continues. Recently I had just put in a new stereo system so with that I had been playing music loud and had not been listening to any noises coming from the motor, until yesterday and really started to hear what was going on.

From inside the car, you hear the knocks upon start up, a mostly quiet idle.. then under any acceleration at all you can hear the knocking noise. again it sounds like a hollow knock to me. that's the best way I can describe it.. It stays in tune with the rpms of the motor, which make me think it is an internal issue, which my mechanical abilities do not cover. so here I am asking for some help from all you knowledgeable jeepers out there!

I've only had the jeep about 3 weeks now, so to have this noise is pretty scary to me lol. while i've had the car i put in a new tranny cooler, just a basic oil change and a tranny flush at my local jiffy lube. the only other thing I've done so far is put in a new t-stat. I was sitting at a stop light and all of a sudden the car overheated.. (this really stressed me out assuming that I have the 0331 head. so the next day i put in the new thermo and she hasn't touched 210 since.
so thinking about that now, could I have not seated the thermo in the head right and that could be causing the knock? to me it sounds like its coming more from the rear of the motor.. not the front.

http://youtu.be/-wnU9LXaLHY?hd=1
^^ this is my car and the knocking noise that is coming from it.

http://youtu.be/cBnx38lK71s
^^ this is the video from the link i mentioned in the beginning, to me the noises sound very similar, but I would appreciate other peoples opinions.

thank you to anyone with some input!
Colter

 

the 0331 head with the defect is 01' year only I am pretty sure. Check the tag on the side of your driver's side door, or write down your VIN # and look that up online. That will give you the model year.

The sound you are having really seems like a loose flexplate before I watched the video, and still thinking the same after I watched it. Check the exhaust front to back and check if it is knocking on your oil pan or anything else.

You can search how to inspect the flexplate, but it is easy. Just unhook the battery, remove the inspection panel, and check for loose bolts. Looking it up yourself is easier than me trying to explain using words I am not sure about lol.

 

Here's a fairly recent thread on Flex-Plate knocking...pretty good thread...I'd start there

https://www.cherokeeforum.com/f51/ho...ocking-125547/

 

If you're running an automatic (AW4) then the most likely cause of your knock (that noise is not lifters) is either loose flex plate bolts or a cracked flex plate. The bolts are notorious for coming loose, though and it's fairly easy to check. Just use the link posted by jamurrin. The longer you run it like that, the more likely you are to crack your flex plate so I'd avoid driving it until you figure this out.

The next possibility (also relatively common and just about guaranteed if you're running a 5-speed) would be a broken piston skirt. This is when the aluminum skirt breaks off of one of the pistons near the wrist pin and falls into the oil pan. It's not the skirt in the oil pan knocking, it's the now unbalanced piston rocking in the cylinder bore as it goes through the compression cycle.



...and finally, it could be a bad rod bearing or a loose rod cap but this is the least likely cause.

 

Thank you very much for the replys (and the other link) I'm gonna check the flex plate in the morning and hope to hell that that is the issue. And not cracked lol.

Colter

 

If it's only knocking on start-up, I'd wanna know what brand of oil filter is on that Jeep.

 

It's not just on start up. You can just hear it more clearly on start up. But just to answer its a Napa oil filter

 

Check the flexplate bolts.

 

California Jeeps can have 6 O2 sensors.
They have 3 cat converters, I think.

 

So after checking the flex plate myself and talkin to tranny shop thought maybe the torque converter had let go.. Had it towed to a tranny shop who's done work on a few family cars. He hardly had it for 10 minutes before he called to tell me it wasn't a tranny issue.. The motors toast.

So that was some ****ty news