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.