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I think it's a flex plate

My '99 Jeep Cherokee w/automatic transmission and the 4.0 inline 6 has suddenly developed a horrible tick at idle and while in gear. The tick is loudest after a cold start but does subside after driving, even as little as 10 or so miles. Today I picked the Jeep up from a mechanic following a routine inspection (during which I had all four tires replaced for $400+) and the mechanic said he wasn’t sure what was causing the sound. The sound is connected to the speed of the engine but I’m pretty sure it’s not a lifter or valve. The mechanic did say that he listened with a stethoscope to the valve cover, the engine block, the oil pan, and the transmission and was unable to isolate anything. Anyone have any experience with cracked or lose flexplates? Thoughts appreciated. Here’s a link to a video with audio I just took and posted on YouTube. youtube.com/watch?v=OQx3xwqLtGg&feature=g-upl&context=G2eca0e2AUAAAAAAAAAA

I had a good guess all ready for you and then I heard the video. My guess was going to be cracked exsaust manifold which is very common on the Cherokees. Plus it would get better as the manifold heated up and expanded. However that sound is too loud to beca manifold leak. I will say this from the CID it did seem to be louder on the drivers side then on the passenger side.

CID = vid, darn auto correct.

So gsragtop if it’s not the manifold do you think it could be a flexplate or torque converter? Do you know if those are common Cherokee issues?

There is an inspection cover over the bottom of the bell-housing which can be removed and the flex-plate, its mounting bolts along with the converter can be inspected for wear or damage or loose bolts…

Caddy is right, you can also disconnect the drive belt. This will eather tell you it’s one of you accessories, or rule them all out.

Removing the belt and looking behind the inspection plate might give you the answer to the ticking but if nothing is apparent I have observed that the 4.0L Jeep engine is prone to valve lifter noise as well as the cracked exhaust manifold ticking. But like the Timex watches they just keep ticking and ticking for hundreds of thousands of miles.

That is very loud, you should be able to identify the sorce using a 5/16" or 3/8" hose about 4 feet in length as a stethoscope. Place one end of the hose in your ear and probe around with the other end.

The inspection cover is rubbing the flexplate. My Jeep does this from time to time. The first time I though a rod was about to go thru the block. Take the inspection plate off and I will bet the sound goes away. Mine started when I ran over a tree limb on a trail ride. Now if it is hot and I hit it with water it will warp and make this noise. It dont take much to warp it and have it hit the flexplate.

I think oldbodyman is right. Loose flexplate bolts make more of a ringing sound.

So my “go to” mechanic confirmed it was indeed a cracked flexplate. He said it was cracked all around the crankshaft. I would have taken it to him in the first place but he’s a few miles away. Should have the Jeep back in a few days once the part comes in from Chrysler. Thanks for all the comments.