Slight and Short Knocking Sound

[MrAnderson]

Well the clicking sound remains. starts up a few mins after startup then goes away after a bit of driving. My oil leak stopped though haha, not sure if that related.

 

[brewed4you]

I'm didn't read the whole thread because its late and I'm going to bed right away but I'm still gonna throw this out there.

Cali-emissions XJ? If so check the pre-cats. Had a similar sound to what you described, took a while to track it down but it just turned out to be the pre-cats rattling.

I heard sounds from clicking to rattling to what sounded like a knock over the time it took me to figure it out. Even had a friend's dad who's a mechanic take a quick look and he seemed to think it was rod knock since it really sounded like it was coming from the oil pan.

 

[Redsnake]

Yes, Cali-emissions w the 2 pre-cats. I'm sure they need replaced so perhaps that's the sound I'm hearing. Thx f the info.

 

[brewed4you]

Just smack the cats or the pipe below them with your hand or a rubber mallet, if they're anything like mine you'll hear them rattle no problem.

 

[gw204]

Try to isolate the location of the noise by sticking one end of a small tube in your ear and holding the other end to various spots on the engine. My guess is you will find the tick/tap/knock down near the crank position sensor/oil pump drive (where the distributor would be on earlier 4.0s).

My 2000 taps from there about midway through the warmup cycle.

 

[Redsnake]

Just smack the cats or the pipe below them with your hand or a rubber mallet, if they're anything like mine you'll hear them rattle no problem.

Smacked the pre-cats several times w/a rubber mallet last night they are quite solid... Doesn't mean they're not clogged, but at least I don't think they're all broke up now. :|

The way my '01 is acting is almost like a vacuum leak when the engine is cold. Want's to over rev a bit when I accelerate... but only for a minute or less after startup. Then it seems to be 'normal' ... so I'm stumped. I need to see if I can isolate a vacuum leak or perhaps it's something else. Not something I've dealt with myself before.

Guess it could be the area where my distributor isn't...

 

[MrAnderson]

Its starting to get louder heres a lil video in which u can barely hear it over all the other noise
http://i1295.photobucket.com/albums...D6E7DE-13763-000006409D68EF3A_zps1fb97c26.mp4

From what ive read it seems like it may be my flex plate, i pulled the inspection cover and had a gander but couldnt see anything alarming and the bolts were all tight to the plate(well the three i could see at least) but ive read that things can appear to be fine but arnt, also would that be much louder?. Ill check it to rattling cats

 

[cruiser54]

Check this out:

Straightshooterjeeps cracked flexplate diagnosis
I removed 3 of the 4 bolts.

Then loosened the last bolt about half way.... I left this one in to maintain connection between the tq and the plate. Just so I wouln't have to fiddle with putting bolts back in too much.

Now the flexplate is pretty much seperate from the torque converter.

Got my flashlight pointed up in there

Grabbed a big flathead screwdriver and started prying on the flexplate

Don't see anything yet

Turn the flexplate a half rotation

Pry again

and there it is! A big fat crack up near the center of the plate.

When the flexplate is loose from the torque converter you can get it to "flex" real good and you just might be able to spot your crack.

Just to be sure you do have one before dissasembly.

It was very obvious at this point, but before pulling those bolts I looked and looked and could never see a crack.

Hope this helps save someone a little time.

 

[MrAnderson]

Well i crawled under while it was doing it today and the sound very much seems to be coming from behind that plate( or at least very near there haha)

Probably gonma swing it by my guy tomorrow amd borrow his ear

 

[MrAnderson]

I need a new mechanic, he says the same the every time... "Dont worry about it" ugh

Wouldnt a cracked manifold cause a ticking sound? Im pretty sure mine has a leak from the sound of things

 

[cruiser54]

Easy enough to check your own self. Didn't I post a link to doing it?

 

[Tony_SS]

Its hard to tell from what you posted by mine was making that exact knocking sound..it would go away with any increase in throttle.

I got upity one day, and floored it though 1-2 gears during which a rod felt the need to punch an escape route through the driver side of my block.

Don't ignore it, whatever it is, and baby it until you find what is doing the knocking, or you'll be like me, replacing the whole farting thing.

 

[JeepXJFan]

Or me which had to do the same. Sounded exactly like a knocking flexplate but ended up spitting out the piston skirt of #6 and both the rings. Newer 4.0's are starting to show some pretty nasty colors as they age. I'm not the only one this has happened to. Mine only had 115k miles on it.

 

[MrAnderson]

Don't ignore it, whatever it is, and baby it until you find what is doing the knocking, or you'll be like me, replacing the whole farting thing.

I always baby my babys. Owned my last car 4 years(94 legend) never floored it... Well till the day i sold it

Mine only had 115k miles on it.

Mine just had its 150k bday

Well, my mechanics no help and i dont have anytime to investigate myself. I do however live 5mins from a jeep chargership. Ill probably run it by there on thursday and have them charge me $800 to smell my oil, hopefully theyll be able to help. Went there once and an older gentleman shop worker was scoopin my Heep and talking about his so i know they got a guy there

Heres to hoping its something easy like the flex plate or a leaky manifold(wanna fo a full tranny service and get some doug thorley headers anyways so those would be fine)

 

[MrAnderson]

Well, the very nice and helpful gentalman Eric at the dealership says it sounds like rod rattle.
He asked me if i have a plan B, to which i replied that i wanna put a stoker in eventully. he suggested i start saving money for it but in the mean time just drive it and dont mind it unless it gets really loud.

 

[JeepXJFan]

Mine started off pretty quiet, and it would come and go. One morning while I was letting it warm up it got pretty loud and let go.