1994 Engine Knock.....i need help

ok so its been a long long while since i have posted an issue with my jeep. just recently it developed a severe engine knock. its driven at least 30 miles a day with no issues besides it getting a little too hot. the sound seems to be coming from underneath the car im not sure what the issue can be but im expecting the worse. i have done some browsing over the internet and i havent found anything specific, i plan to get a video up ASAP so you guys can maybe come up with a diagnosis. it also just started to have a rough start again. i fear it may be the starter but i have a warranty on it so im going to get it replaced. that is all i can think off the top of my head so let me know what you guys can come up with and if you need any more info off me i can provide. thanks and appreciate the help.:shiver:

Cracked flex plate would sound like that and may affect starting.

Or they may not be related.

Ecomike said:

Cracked flex plate would sound like that and may affect starting.

Or they may not be related.

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i dont think so im going to have the starter and battery tested out tomorrow. but as far as that cracked flex plate does it affect drivability ? and how do i go about fixing it ? thanks:spin1:

sorry forgot to add that its a 2wd 4.0 HO the original owner swapped out the engine before i had purchased it so it is still running strong.

cz94xj said:

i dont think so im going to have the starter and battery tested out tomorrow. but as far as that cracked flex plate does it affect drivability ? and how do i go about fixing it ? thanks:spin1:

How long ago did he swap the engine? He may not have properly tightened the flex plate bolts?

sorry forgot to add that its a 2wd 4.0 HO the original owner swapped out the engine before i had purchased it so it is still running strong.

Note that the flex plate has the gear teeth on the outer rim which is where the starter gear teeth mesh and turn the crank shaft. The two problems may be a cracked flex plate!

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If it is cracked, it must be replaced. Do not drive it if it is cracked, it connects the engine drive shaft to the transmission torque converter!!!

You need to pull the front cover next to the starter on the Tranny bell housing and manually turn the crank shaft and inspect the flex plate for hair line cracks. Pulling the starter will give you a partial view of the plate.

Ecomike said:

If it is cracked, it must be replaced. Do not drive it if it is cracked, it connects the engine drive shaft to the transmission torque converter!!!

You need to pull the front cover next to the starter on the Tranny bell housing and manually turn the crank shaft and inspect the flex plate for hair line cracks. Pulling the starter will give you a partial view of the plate.

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i bought my jeep last Feb and i belive the engine was swapped in 2011 probably around june i cant remember when exactly it was done. whats the difficulty on that ? and what do i look for when i take off the starter ?

cz94xj said:

i bought my jeep last Feb and i belive the engine was swapped in 2011 probably around june i cant remember when exactly it was done. whats the difficulty on that ? and what do i look for when i take off the starter ?

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Loose bolts to the crank shaft or the torque converter, and any sign of a crack in the plate.

Ecomike said:

Loose bolts to the crank shaft or the torque converter, and any sign of a crack in the plate.

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ok then i will tomorrow also check back tomorrow i will have a quick video see if that helps. before i take off the starter:flipoff: thanks i appreciate any and all help .

Agreed... what's your oil pressure like?

Pull the inspection plate off and use a breaker bar to turn the crank slightly while watching the flexplate. If there is no play you may be ok, if there is play between the crank pulley and the flexplate/starter ring gear your issue is probably the flexplate.

If you can get it started again listen to where the noises are coming from. Bellhousing? Probably the flexplate or torque converter. Engine/oil pan? You've got bearing issues or a dropped piston skirt.

I'd bet on a flexplate, but verify before tearing anything apart too much.

kastein said:

Agreed... what's your oil pressure like?

Pull the inspection plate off and use a breaker bar to turn the crank slightly while watching the flexplate. If there is no play you may be ok, if there is play between the crank pulley and the flexplate/starter ring gear your issue is probably the flexplate.

If you can get it started again listen to where the noises are coming from. Bellhousing? Probably the flexplate or torque converter. Engine/oil pan? You've got bearing issues or a dropped piston skirt.

I'd bet on a flexplate, but verify before tearing anything apart too much.

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id have to check it again i cant remember what the oil pressure but it should be in the normal range. i did an oil change id say 5 months ago i switched to synthitic oil. i dont know if that ended up hurting it. ill have a video tomorrow while its running before i take off the starter

Here's a simple write-up, with photos, regarding loose flexplate bolts. The same info will get ou to where you can see the flexplate. Heck, it could be just loose bolts!!

http://www.cherokeeforum.com/f51/how-fix-flexplate-knocking-125547/

cruiser54 said:

Here's a simple write-up, with photos, regarding loose flexplate bolts. The same info will get ou to where you can see the flexplate. Heck, it could be just loose bolts!!

http://www.cherokeeforum.com/f51/how-fix-flexplate-knocking-125547/

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Thanks for that I will do this tomorrow. Sorry I been busy and haven't check this. Is there ant body in San Diego that can come check it out ? I would like someone to help our solve this issue. I'm unemployed and need my car up and running I can pay money but not ridiculous amount. Also beer and food. Let me know if any body. Can thanks

Is there any down here in San Diego California that could help fix this up I'm unepmployed and can't pay a lot

CAT?

xcm said:

CAT?

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LOL, seeing that avitar of yours, and the entire post "CAT?" was just too funny!!

:laugh2:

But good point, busted Cat, rattling guts inside maybe.

cruiser54 said:

Here's a simple write-up, with photos, regarding loose flexplate bolts. The same info will get ou to where you can see the flexplate. Heck, it could be just loose bolts!!

http://www.cherokeeforum.com/f51/how-fix-flexplate-knocking-125547/

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thank you for your help it ended up being the flexplate bolts literally falling off. but like always with my luck a new issue arouse i will be posting up another thread in the hope of finding the issues. thanks again

Since we're already on this topic, please allow me to chime in here. New member to , and I've searched this topic over and over, so please bear with me.

I have a '99 XJ, Auto, 4.0 (Dana30/Chrysler 8.25) 201,000 miles. Just purchased last month. Totally love it, as it's the 2nd XJ I've owned.

So, just recently I've had this 'engine knock' as well. Hasta


The sound is definitely coming from the lower end of the engine, right about where the flex plate/tranny meet. I took a quick peek today, removed the insp. cover, all 4 outer bolts were tight. It didn't quite look like there were any cracks in the flex plate, but then again it was kinda hard to see up there.

I assume the cracks are more likely to appear towards the center of the plate where it mounts to the crank? Is it possible that the inner bolts are loose? It may be cracked but I'll look again to be positive.

Ok, so like I said, no noise from up top, only from underneath.... so how do I tell if I have a bad rod bearing?

At this point I'm either for the cracked flexplate, or a rod bearing, but would like to try to narrow it down if possible. Either way, something has to come off either the oil pan or the tranny (but I hope not).

I have heard of piston skirts breaking off too...

The oil pressure seems just fine, fresh oil change and filter too. The thing runs like a champ but the noise is scaring me....it's either an OME lift kit or a bunch of engine work at this point....lets hope it's an issue that's not entirely engine related.

I'll get a video up tomorrow if that will help...any requests while doing so?

Thanks.

BTW, Great forum here, glad to become a member!:cheers:

Westfield mass? Or somewhere else?

The crank to flexplate bolts can come loose if someone didn't torque them right but I've never seen it personally. Cracks do indeed form up near the center where you said.

Try goosing the throttle, listen for a rattle. Try to locate where it's coming from with a mechanics stethescope.

Yeah, Westfield MA.

I thought I heard some noise a couple times driving it around town. When I drove it from Palmer to Westfield I had no noise at all....don't think. When I goose it (in park at idle) the noise seems to go away at a higher rpm...in fact I've noticed a couple times while driving it, if I rev it up to a point, I hear a rattling noise right before it shifts, and then the sound disappears once it shifts (drops rpms)...so the sound changes under a load maybe?

What about pulling plug wires while it's running...would that narrow out my options?

How much difference would it make, with a stethoscope, between the last piston (back of the oil pan) and the flexplate? I was underneath it today while idling and the noise is right at the drain plug...right up in there somewhere, can't tell if it's the tranny side or the engine side...that's all.
Thanks for the quick reply too :cheers:

Sounds like a loose flex plate bolt, or crack. There are 8 bolts total, not just 4 IIRC.

Ecomike said:

Sounds like a loose flex plate bolt, or crack. There are 8 bolts total, not just 4 IIRC.

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4 flexplate to torque converter bolts.