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Hey guys, I recently bought my first Jeep - '95 YJ w/ 4.0. Been loving it so far, but I'm hearing a low-rpm ticking/tapping noise, and I'm trying to figure out if it's normal noise for these engines or something to be concerned about. I hear it mostly in low-load situations - idling, coasting in gear, light throttle, etc. As RPM goes up, it gets faster, but not louder, and it's quickly drowned out by other exhaust/air intake noise. It seems to be coming from the top end of the engine.

Here's some audio if it helps:
1 - idling with hood down
2 - close in with hood up
 

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Lifters get gummed up and tick on these engines. If you do a engine flush with seafoam it will help clean the lifters out and the tick will go away. 4.0's do have a lot of valvetrain noise so there will always be some dieseling noise but it'snothing serious these engines will run for 300K+ easy with regular maintenance.

Follow the instruction on the seafoam can i think it's 1 ounce per quart of oil for a flush. the 4.0 holds about 6 quarts so you would use 6 ounces. Drive it for a while let the seafoam do it's thing then change the oil. You can also use a larger Wix 51515 oil filter they are cheap and the part number is easy to remember.
 

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So I put about 6oz of seafoam into the oil Friday night and since then I've driven about 60 miles around town. So far I'm not noticing any difference in the noise. The bottle does say to leave it for 100-300 miles, but I could swear I've seen youtube videos out there where it makes a pretty quick impact. I'm curious what other people's experience has been - how long does it normally take to do it's thing?
 

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So I put about 6oz of seafoam into the oil Friday night and since then I've driven about 60 miles around town. So far I'm not noticing any difference in the noise. The bottle does say to leave it for 100-300 miles, but I could swear I've seen youtube videos out there where it makes a pretty quick impact. I'm curious what other people's experience has been - how long does it normally take to do it's thing?
Sometimes it takes a couple treatments. As these old heaps age, the previous owners start to defer maintenance. Longer and longer between oil changes and the crud builds up. I had an occasional loud lifter clack upon start up when I first got my Jeep. The first Seafoam treatment reduced it a lot and the second one cured it completely. I don't drive the Jeep a lot so I change the oil in the fall and the spring.

Good Luck, L.M.
 

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My 4.0 had a bad knocking sound that developed at about 70k on startup. I didn't know what it was at first and i was a stupid teenager at the time fearing the worst. Back then i used to run penzoil and fram filters but i did change my oil religiously. Then over the years i switched to castrol, then castrol synthetic blend. The loud knocking at startup was sporadic and eventually i realized it was a lifter and tried flushing it with various things including a quart of ATF and marvel mystery oil.

Eventually i tried seafoam and it did take about 2-3 treatments and now with 120k on it i haven't heard it in over a year. I run seafoam though the crank case about once a year now just to help flush any gunk out of the lifters and it continues to run like new. I have about 200,000 miles left to go before i need to start thinking about possibly rebuilding it unless i decide to build a stroker. I also run full synthetic mobil 1 oil now and a Wix 51515 filter not sure if the oil helps with lifter knock or not.

I would let the seafoam sit longer and help break up crud. Then change the oil and next oil change run 6 more ounces in the oil for a week or so and change it again, 99% chance it will go away. But these engines will always have a faint dieseling sound at idle that will never go away.
 
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you might find this video useful

 

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On the gentleman’s zinc rant, I used Amsoil Z-rod oil and didn’t notice any improvements vs regular Amsoil 10w-30, both did have zinc but the Z-rod was supposed to have much more.
I got into the zinc hype when it first started back in the early 2000's. At first i was running a STP additive then they removed zinc from it or drastically lowered it. Then i started running 2 ounces of Lucas ZDDP additive in my current jeep and some other jeeps i owned. Sometimes i was busy and forgetful and i never added anything. Long story short i dont think Zinc as as important as some people make it out to be. If i was breaking in a new flat tappet cam i would use oil with a lot of zinc until it was broken in. After that i think you would be fine with any oil.

If i build a stroker with a high lift cam i will be running high zinc oil but currently I'm running regular off the shelf oil. I have done it in the past in other jeeps with no catastrophic cam/lifter failures along with 99% of jeep owners that are clueless about zinc.
 

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The issue with zinc or zddp is that it will wipe any catalyst equipped vehicle out in pretty short time. It is a great lubricant and should be run in any motor because of the benefits it provides but it does not play well with catalytic converters. It will take out your cat.

So if you do not have a cat, run Rotella or other diesel oil for the benefit of zddp and the extra detergents that diesel oil has with out Any ill effects. It’ll keep your gas motor well lubed and clean.
 

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Discussion Starter #14
Thanks for the input guys, appreciate it! There were a couple mentions of lifter noise on startup - is that normally when lifter noise happens? Wondering because mine is the opposite - it sounds fine on start up and the noise kicks in as it warms up. Pardon my ignorance, this is the first pushrod engine I've had.
 

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You may want to run a slightly heavier oil, depending on the climate where you live and the amount of wear on your engine. I used 10w30 since that is what the manual says, but my I6 really didn't like the thin oil. Could be that I live in the warm-scorching hot California Foothill. But I use Rotella T4 15w40 exclusively year round now and the engine is much quieter. I also started using engine restorer after reading great reviews, and have seen a decrease in blow-by and overall better performance.
 

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Mine too is the same, as it warms up it gets noisier. I‘ve tried all sorts of engine flushes and Seafoam but it really didn’t change much of anything. All sensors are new, complete new cooling system, new timing chain etc... Literally there is nothing more to replace with new short of rebuilding the long block.

I suspect that more than one lifter is bad so I’ll just live with it as the motor runs strong enough, doesn’t use or burn oil, the compression and oil pressure are within spec. Oh and it passes California smog with flying colors.

I‘ve been running mobile one 15w50, five qt jug from walmart, wix 51515 filter, and one qt Lucas oil treatment for the last couple of oil changes.

This should get me by until I build my stroker 4.6!

so what I’m saying is just do all the services and just run it.
 

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My 95 Wrangler (118K miles) has the same ticking noise. I everything looked good and clean when I had the valve cover off earlier this year. The idle is a little rough also (when compared to my 2005 buick Rendezvous with the 3.6L)
 

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For about the first year I had my Jeep, I had a rattle type noise that I couldn't find. It was pretty constant and seemed to vary with RPM. I listened all over the engine with a mechanics stethoscope, a rubber hose and a long cardboard tube. With all the noise the fan was making, I couldn't determine an exact location. It seemed toward the front of the motor.
As an aside, my timing mark was jumping around when I tried to set the timing. I installed a HEI distributor and changed the timing chain. I discovered that the timing chain had stretched and was contacting the front cover. Apparently that was the noise I was hearing, because once it was all back together, the noise was gone.

Pic 1 shows the rubber snubber gone and some of the front cover worn away.
Pic 2 shows how loose the chain was.

The timing chain may not be the noise that michter964 and jhess169 are hearing but it's something to consider.

Good Luck, L.M.
 

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