I have a 1996 Cherokee. For the past year and a half my jeep has had clear rod knock. In the last two weeks, the rod knock just randomly dissapeared. What does this mean. I've never heard of a rod knock going away before.
I've been in the process of saving for a new engine because of this knock.

Any suggestions?

 

I have no idea how it might have just disappeared on its own. Are you absolutely sure it was your rods?

Do you do any of your own work? With a good manual rebuilding an engine is actually not that hard if you have all the right tools. If you want, instead of waiting to throw a rod or something go ahead and find a block from a junkyard or whatever. I have heard of Pick N Pulls having 4.0L HO blocks for sale for $75-$100. Anyway, stick the block on an engine stand and get to work while waiting for your other engine to blow. Hopefully you finish building up the new engine before the old one goes. Then all you gotta do is swap the engine out.

You'll have to take your heads and block to a good machinist to have some work done, but other than that you should be able to do everything yourself in a garage.

Just an idea.

 

Thank you for the advise.
I am fairly sure that it was a rod knock. Several other people ave claimed it to be a rod knock as well, this is why I was confused when it just up and disappeared.
I do all my own work so I shall take your advise and start looking around and building. If not i may just scrap it and start fresh on a new Cherokee.

 

Either way you should do a build thread.

 

A rod is not going to knock for that long without letting go in a very ugly way. So here a couple of questions for you.

Does the knock get louder when sitting still at a redlight?
Does the knock subside when under a load such as acceleration from the redlight?
When idling in park does the knock increase in speed when the engine is revved?

If you answered yes to any of these then you need to check your flexplate for cracks. A broken flexplate will create a knock that will fool most "mechanics" into thinking that the bottom end of the motor is trash and needs a rebuild.

 

X2

 

Some times an injector can make that sound if its not firing right

 

rod knock won't go away until the motor stops running.

must have been something else knocking. lots of stuff can do it... sometimes exhaust leaks can sound like a rod knock too

 

Nope, the knock would get louder and faster when i accelerated.

 

Sounds like flex-plate.

Also check exhaust manifold (cracked)
-or-
Dying catalytic converter. When cats die they dont ALWAYS clog, they break apart and the remnants can sound like maracas (sp?)

P.S. A rod knock will sound like a 25lb sledgehammer in a cement mixer.
If it goes away--the Thread will be titled "Strange metal protruding thru oil pan, oil everywhere..HELP!!!"

This bit of information comes from very recent personal experience.