I have a 98 inline 6 grand cherokee, its been making knocking noises for awhile now. Im trying to figure out what it is and where its comming from.. At times it sounds like its comming from the fan belt, however if you listen more closely its more comming from where the exhaust starts on the side of the engine or near where the Valve cover is.

6 years ago the engine broke a number 3 valve spring and the whole car was shaking like crazy. It took them awhile to figure out what was causing it and it was a broken valve spring.. Number 3. The engine has 160k miles on it and it runs great, it drives extremely smooth and sounds good from inside the vehicle.

The only time i hear this ticking or knocking is when the vehicle firs starts up cold you can deff hear it. When it warms up it kinda goes away however if you drive at a McDonalds drive through or something where the wall reflects the engine sound at you, i can hear it again and this time its really clear. Sounds like knocking. If the engine is revved passed 1000 rpm the knocking goes away, when you go back down the knock comes back and its deff going at the same pace as the RPM's.

Ive listend to video's on youtube and it doesnt sound nearly not even close as bad as those knocking video's.. However you can hear it nonetheless. All the engine fluids were changed, along with transmission and transfer case. Had a tune up, new plugs, new coil, new cap and rotar, new filter ect... Also cleaned the engine from top to bottom as it was coverd in old oil and filth.. The engine did have a small oil leak in the back of the valve cover near the rear spark plug however it hasnt been leaking since i changed the oil to a Synthetic Blend about 600 miles ago.

Here is a video of the noise.... Im sorry you cant really hear it that good because the noise from the engine overall is masking it... However if you rewind the video on some parts and listen closely especially near the end of the video starting at 1:00 you can hear the knocking sound.

 

Well no one has any idea's ?

I'll try to make a better video i guess... This morning tho i opened the hood and used a long plastic tube to try and find where the noise was comming from.. I dont hear any knocking comming from the valve springs they sound fine. The ticking noise is comming from the fuel injectors so thats normal.. I couldnt really narrow down the knock sound, only that it is comming somwhere on the driver side of the car, near the exhaust manifold. You can hear the noise best if you kneel down and listen where the front driver side tire is

I moved the hose as best as i could on that side but i kept touching the exhaust pipe and burning the hose.. However there was one point where i did hear the noise pretty clearly against the engine block about half way down under the exhaust manifold. It sounded like clenk clenk clenk clenk sorta ? It went away for the most part after the engine warmed up, it goes away after the engine is revved above 1k rpm or so also.. It does sound like it goes faster as the engine gets up in rpm but then it disapears as the engine revv's.

The other side of the engine i couldnt find a single noise comming from the engine block except where the ignition coil is in front of the distributor cap when pressed against the engine block right next to the coil i can hear ticking noises that sound like a Pellet or beebee machine gun. This noise didnt sound like the knocking however.

 

Well, guess n oone knows what this noise is.....


I made a new video.. you can deff hear it on this one... Please listen to it and tell me what you think... Its no louder or softer in person it sounds exactly like it does on the video i made..

 

Bump another video i made .....

Someone on another Jeep forum said its the flexplate.. So i put my camera under the car and turned the engine on..

I went under and it does sound like its coming from the transmission flexplate, or right under the oil pan.. Its deff comming from that area i belive.. Im thinking of taking the inspection cover off and looking at the flexplate and see if the bolts are loose or something.

Here is another video i made..

 

Cut small piece of gardener hose and listen to engine. Knocking while cold will indicate low oil pressure and then oil pressure build up and noise are gone. It could be your oil pump, main bearings, rod bearings.
At the beginning I heard high pitch noise while starter being engage. It sound like the gears not engaging correctly. It could be loose starter bolts or crack back plate (flywheel). The rest of the noise is not recognizable to me.

 

The noise you heared in the beg was just the exhaust, my phone if the noise is to loud starts to cut out sorta, the noise you want to listen too is the knock, knock ,knock.. You heared that right ? The oil pressure when cold is actually higher then it is when warm, it goes up and down when cold from like 30-36-40 ect.. Onces the engine warms up for like 5 minutes the oil pressure settles and stays at 30 until i drive off, to which it will climb to near 40 if the RPM's are high enough or if im going up a hill.


Yea i cut a tube earlier and listend, its not comming from the engine block on either side top or bottom. Its not coming from the oil pan in the front or the back. It is however coming from right here.. I couldnt tell if it was the oil pan on the side or the inspection cover where the torque converter is, since the tube end i cant flex it to aim directly at the cover.. It just goes up, however it got louder the further i shoved the tube where the red mark is.. So its probably not a lifter, or anything like that correct ?

Im starting to think that it actually is the flexplate or the torque converter bolts. The only problem is when i tried to take the inspection cover off, i noticed the starter is bolted right on the cover, and it seems the cover goes all the up on the sides of the engine also not the just the bottom... So im wondering how the hell do i get this thing off.

click the pic to enlarge, this is not actually my picture but one i found they are pretty much the same looking tho


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it's not like a purge valve or anything is it? it's def an engine knock and not just a tick or clunk from under the hood?

 

If that is where the noise is coming from? That picture is showing where the rear main seal is. Parts are not expensive but it is time consuming to replace. You have to drop the oil pan. Too drop the oil pan you have to jack up the motor. Then you have to remove the rear main bearing.

 

I found out what it was, its the flexplate. I had a neighbor check it out hes a mechanic and works on his own Jeep, and he confirmed what i thought it was and the flexplate is cracked.