• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Mysterious tick


NAXJA Forum User
I have a 1990 4.0L automatic XJ with a fun new tick that I’m trying to diagnose.
After starting, 10 seconds later the ticking starts. It’s random, not rhythmic. When i put it in reverse, the ticking increases. When i increase the RPMs, the ticking increases. It usually goes away after a minute or two, but a couple times it has remained and gotten worse. I went back home and parked the jeep those times.

The flex plate bolts were tight. I took 3 of them off and loosened the 4th and gently pried on the flex plate with a screwdriver. Didn’t see any cracks. Rotated it 180 degrees and pried again: no visible cracks. I thought maybe the bendex gear of the starter wasn’t retracting, so i swapped out the starter since it was under warrantee; no change.

I did recently replace my rear main seal and oil pan gasket; while i was in there i replaced my oil pump. I put in the melling HV model, but didn’t have any clearance issues. I’ve heard of dipsticks vibrating on the oil pump pickuptube, but i pulled mine and the tick remained.

With a mechanics stethoscope I’ve probed the oil pan, bell housing, distributor, cps, and everything else i could think of, but never heard/felt the tick in any of those components.

Do you guys think it’s cracked flexplate with invisible cracks? With the bolts out the holes didn’t seem ovalized, but possibly enlarged? Let me know what you guys think. Thanks!

Cruiser—your tips have been super helpful for me, thanks for the time you spend helping people with their jeeps!

This morning I started it and had the tick immediately at a fairly high rate. I waited 30 seconds or so and shut it off. Waited 10 seconds, restarted it. For about 20 seconds there was no tick and i was holding my breath hoping it would stay gone. But it slowly came back.

Are you thinking maybe the oil is draining out of the filter while it sits?

I’m running rotella 15w-40 and a wix filter. I’ve been meaning to replace my oil adapter o-rings as i still have a small oil leak at the rear of the engine even after replacing rear main seal, oil pan gasket, and valve cover gasket.
If my answer comes in a $7 bottle I’ll be very happy. I replaced a quart of my oil with some MMO. No immediate effect, but I’ll give it some time to work its magic.

I’ve had a tick before that two mechanics assured me was lifter tick, but it sounded very different. It followed the RPMs much more closely and putting it in gear had no effect. This sounds much more tinny. But i suppose stuck/collapsed lifters can probably manifest in different ways.
Alright so I drove the jeep to work today to get the juices flowing and have an update:
While I’m driving along and it’s ticking away and i throw it in neutral, the ticking immediately stops. Every time. If im at a stop and i gun it in drive, it ticks very rapidly. If i gun it in reverse it does not tick, until i hit the brakes.
This makes me feel like the motor shifting to the rear exacerbates the tick and has me looking towards the transmission. Any thoughts?
My fan shroud is off at the moment, but thanks for the response! I’m crossing my fingers it’s something simple like that. I’ll be embarrassed for posting on here, but happy.
I know noise locations can be deceiving, but it really sounds like it’s coming from the bottom end, bell housing/rear oil pan area.
Check your distributor shaft, up and down play doesn't mean much sideways play does.
My 96 did the same thing, I ignored it, and eventually, my rotor exploded. My best guess is motor harmonics (speed, load etc.) played a role in how bad or when the tick happened.
I'd keep a spare rotor in the glove box just in case I'm on the right track. :)
Thanks for the idea! Id stethoscoped the distributor already looking for vibration, but after your comment i pulled the cap and rotor and checked the shaft. No side to side play.

On my drive home i went up a steep hill which reeeally increased the tick to a scary buzzy chirpy level. It seems to really hate weight shifting rearward.
I think I’ve thought of it, and if I’m right I’m embarrassed. While installing my valve cover, i dropped the rearmost bolt. I didn’t find it under the jeep but figured it probably landed on some bracket and would fall out as soon as i drove off. I thought “everything is all sealed up back there, it can’t do any damage.” I found a new bolt that would work and installed the valve cover. What i didn’t realize is theres a hole on top of the bell housing. The bolt could have totally fallen in there, which would explain why the rattling changes with vehicle incline. I’m going to try to fish it out with a magnet and cross my fingers i don’t have to drop the transmission. Any advice would be appreciated!
If you are talking about the hole in the top of the bell housing that I think you are you are not in bad shape.
Guys here and there have dropped one of the CPS bolts down there.
Appears that they do find their way to the bottom and guys have been able to fish them out with taking off the small portion of the flexplate cover so.....
Welp, i couldn’t seem to find a loose bolt knocking around in there. After thinking about it some more it was a pretty farfetched idea. That would have been much more dramatic/catastrophic.

I backed the jeep up onto some ramps. Tilted forward, it would not tick. As soon as i drove it down off the ramps onto flat ground it started ticking again.
SO i have an idea. My transfer case is starting to get a loose chain i believe from driving too much in part time. Sometimes i can hear a a noise coming from there. try and put your hand on the transfer case lever and feel for vibrations while driving. also check the evap canister ?
Will do!

Today i dropped the oil pan and replaced the hv oil pump with a standard one. I thought it might be pumping too much oil and starving. No change to the tick.
It’s fixed! I shimmed the top of my starter with a washer and the noise is completely gone. The bendex gear must have been coming in contact with the flexplate while running. Thanks to everyone who threw out ideas!
Wow. Never would've thought of that

Sent from my SM-G996U using Tapatalk