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Solution for odd rattle at idle

rocknxj

rocknxj

NAXJA Forum User
Location
Clinton, Utah (SLC area)
I tried for over a year to diagnose an odd rattling noise during engine idle. I listed closely to every square inch of the engine bay, pinpointing the rattle sound to the oil pan/flywheel location. I thought it was a loose bracket or heat shield at first.

The sound progressively worsened and I had a few NAXJA members verify the location and give a few pointers. A few suggested I check the flywheel bolts. A loose flywheel would cause an odd noise, they claimed.

Tonight I decided to remove my transmission inspection cover and I was blown away at what I found. All four flywheel bolts were so loose I could turn them with my fingers. I removed the coil wire, tighten the first bolt to the required 105 ft lbs, and had my kid turn the crank shaft. I re-torqued all four bolts, then double checked for good measure. Reinstalled the inspection plate, connected the coil wire, and started the engine.

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My engine roared to life and for the first time since I've owned it, purred like a kitten. No rattle sound noted whatsoever. Bottom line, check those odd sounds and fix them before something bad happens. I cannot imagine the carnage that would result if the bolts backed out any further.
 
Ok, just for terminology, flexplate for an automatic transmission, flywheel for a manual.

The torque converter to flexplate mounting bolt should be treated with Locktite or you will be back under there again very soon.

Good luck.
 
joe_peters said:
Ok, just for terminology, flexplate for an automatic transmission, flywheel for a manual.

The torque converter to flexplate mounting bolt should be treated with Locktite or you will be back under there again very soon.

Good luck.
Click to expand...

Flexplate. Got it. Dang book I used for torque spec calls it a flywheel.
 
You might want to double check the torque specs. I thought I remember reading the flexplate To the crank is 105 ft lbs, the torque converter To flexplate is 28 ft lbs.
 
Would this seriously sound like a heat shield rattling? Just the last couple of weeks my 98xj has had a similar "rattle" and I just assumed it was the heat shield on the catalytic converter, but when I inspected it it wasn't loose.
 
same thing happened with me last week! 3 of the 4 were backed out over halfway.
 
samson-sounds a lot like that. that's the first thing i checked, in fact, when i heard the sound.
 
iwannadie said:
You might want to double check the torque specs. I thought I remember reading the flexplate To the crank is 105 ft lbs, the torque converter To flexplate is 28 ft lbs.
Click to expand...

To be perfectly honest, I did not torque the bolts because I had no way of holding the plate stationary. I just tightened them down. Hope I did not mislead anyone with my initial post. Hey, I'm learning as I go.
 
Nice post... gives me something to look/check on my '96XJ w/ 242K miles on the clock. I've got more than one rattle and noises... but it doesn't hurt to check this if it's a common issue.

How long did it take you (estimate) f/ start to finish on this one being as it'll be my first time doing this particular job too.

I've changed clutches on my Mustang Cobra a few times in the past... so how hard could this be right. :)
 
rocknxj said:
I removed the coil wire, tighten the first bolt to the required 105 ft lbs, and had my kid turn the crank shaft. I re-torqued all four bolts, then double checked for good measure.
Click to expand...

I read it as you torqued it down to 105, either way hopefully someone will post the correct specs for the torque converter to flex plate...
 
Dang, missed that.

Ok, depends on the size of the bolts:

10 mm are 23-27 ft lbs.

12 mm are 40-43 ft lbs.

Either ones they should be Loctited.
 
I'll post some quotes from my Haynes manual later tonight. They do some goofy crap, like have you follow the installation directions from an earlier section (2A), but use the torque specs in Section 4...something like that. Of course, I probably goofed when I looked up flywheel instead of flexplate, which probably explains the discrepancy with the torque values.
 
Those "generic" manuals try to cover too many years to be worth anything.

Earlier XJs you can purchase LICENSED reprint copies of FSMs on CD for about $37 from Bishko direct or on eBay. Don't buy the pirated junk, waste of money and illegal. There is another company that is the original publisher but the name escapes me right now. You can often get original print FSMs on eBay and Craigslist. They are worth the investment.
 
joe_peters said:
Those "generic" manuals try to cover too many years to be worth anything.

Earlier XJs you can purchase LICENSED reprint copies of FSMs on CD for about $37 from Bishko direct or on eBay. Don't buy the pirated junk, waste of money and illegal. There is another company that is the original publisher but the name escapes me right now. You can often get original print FSMs on eBay and Craigslist. They are worth the investment.
Click to expand...

I took a look at my Haynes manual tonight. They refer to the item as a Flexplate/Driveplate and do not distinguish the difference between auto or manual transmission. Also, the removal/installation procedures are only covered in the 4-cylinder section. The I6 section only points you back to the 4-cyl section, but gives a caution to use the torque specs in the I6 section, which is stated as 105 ft lbs.

This is where I got the info, and I'm not suggesting it is right, but that is my source. I said I torqued the bolts to 105 ft lbs in my initial post, but that was done to make reference to what I thought was true, based on direction from the Haynes manual. In reality, I just wrenched on the four bolts with what I could do with a 15 mm wrench. Probably way below the 105 ft lb value, which is a good thing as I may have broken one of them.

Hope this clears up any confusion. I'll check into the FSM as a better source. Thanks, Joe, for putting up with me and my rantings.
 
So Let me get this straight.... I don't have to pull the entire trans to tighten the flex plate? I've got a 96 XJ I6 with the similar symptoms for months now and there is an access panel to tighten the 4 bolts to fix this rattle trap? WTF?
 
You would have to pull the entire trans to tighten/torque the flexplate to crankshaft bolts.

To tighten the torque converter to flexplate bolts you only have to remove the inspection plate.
 
I've been searching for something similar to my issue for my 92 XJ for a while now...searched NAXJA up and down then...lol Google ftw ;-)

Thanks for the post guys, I will be checking this first thing tomorrow.
 
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