Awful engine knock in the front, sounds like rocks inside

1989 4.0L

Few months ago a small tick/knock developed from the engine that didn't seem to be much of an issue. Was only barely audible at idle.

Now, the knock has suddenly gotten a LOT louder. It sounds like a bunch of rocks in the engine. I used a screw driver as a stethoscope and couldn't hear much on the valve cover, but if I put it on the cylinder head at the front just beneath the valve cover I can hear a little bit of some rustling around. I put it on the bottom of the oil pan and only heard whirring of the crankshaft.

Could it be a main bearing or wrist pin on the #1 cylinder? I can't hear it at freeway speeds but around town its really loud. Maybe the front harmonic balancer or timing chain?

Don't tell me I've just blown up a Jeep 4.0

the tell tale sign of the balancer going bad is that it walks in or out. it is two pieces and after time the rubber separating the two pieces begins to wear causing it to bulge out and hit the mech fan. its worth a look but when mine did that it didnt sound like rocks. have you drained or at least checked the oil for anything obvious?

X2 on harmonic balancer. Have you looked for rub marks on your timing chain cover?

Got a video of the noise.

http://www.youtube.com/watch?v=cl8fn8FWWyo

Sounds more like it has something to do with either a cracked manifold, or a vacuum leak of some sort....in my opinion.

Is it worse with the oil cap off?

Its easy to quickly narrow this down. Take the belt off and run it, and make sure the noise is still there. Also lay underneath the jeep and look at the back of the balancer, if its rubbing the timing cover there should be a shiny spot on the back of the balancer.

That kinda sounds like the harmonic balancer rubbing on the timing cover to me. I agree on pulling the belt and checking everything. I had a nasty knocking sound that turned out to be the alternator rear bearing.

Turns out it was 100% the waterpump.

Took it out and it was really loose, the bearing went. New one is in and it's all better.

dont forget too plug youe electric fan in aswell! thanks for the video also and closing the thread!

mattbred said:

Turns out it was 100% the waterpump.

Took it out and it was really loose, the bearing went. New one is in and it's all better.

Click to expand...

Exact same thing happened to me. Same sound like rocks in a blender. I always thought that a water pump would leak as a first sign of trouble. Taking off the belt found and confirmed the source of noise.