Engine Noise Info Condensed - JeepForum.com
 
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post #1 of 1 Old 08-14-2016, 08:58 PM Thread Starter
TheMrCalcovaify
Registered User
1998 XJ Cherokee 
 
Join Date: Mar 2011
Location: Cedar City
Posts: 14
Xj Engine Noise Info Condensed

Hey, I am one of those "thread readers" but rarely post. However in researching an engine noise I have been experiencing I have found that finding any info has been a mess. So in an effort to condense relevant info I have made this thread. So this is what I have found out so far (with edits to be made in the future);


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Collapsed Lifter
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When a lifter collapses there is hard metal on metal contact... Some times it primes just long enough to tap... then the next hit it knocks. Thats all I can come up with as to WHY...

When you shut engine down, take the oil fill cap off and LISTEN.... Do you hear a whistle sound or grunting sound? That was something both mind was doing after shut down.. When I had the valve cover off I could watch the rockers slowly
do down while hearing that. It was the lifters bleeding down.. WAY faster than they should...
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Stuck/sticking lifter
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you'll hear a flutter in your exhaust, like a sticky/worn valve would do, AND you would hear a pretty distinct tapping noise, like a collapsed lifter but maybe not quite as loud.with ticking that happens
intermittently, it is definitely your lifters. Regardless of the temperature of the engine, or the engine rpm, the ticking will continue to happen intermittently.Lifters will usually only make noise at
idle speed and will usually get quite at higher engine speeds.
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How they work
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Hydraulic lifters are a new concept to me, but here is what I know. They are about the size of half a role of quarters. They have a spring system inside that is actuated by oil being forced into the lifter. The pressure causes
the spring to move and this in turn allows
the valves to open and close. If the oil passages on these lifters become clogged with engine varnishes or other grime, they start to fail and the ticking noise I assume is valves out of sinc, possibly even hitting the piston. I am not
sure if the valves are able to hit the pistons on this particular engine, but even if they can't, there is power loss due to valves not being open or closed at the right time. These lifters are also acquated by the movement of the cam,
which they come in contact with. Like I said, this concept is new to me and I might be wrong on some of this, but all I can tell is that this is not a problem that should be taken lightly as it can do some damage and at least causes
premature wear. I like my engine and want it to last another 100,000 miles. Therfore, I am determined to solve this ticking noise.
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broken piston skirt
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I unhooked the power to 1 injector at a time, listening for a change in the noise. When I unhooked injector 6, the engine was much quiter, so I assumed that was the bad piston. Pulled the pan, and that was correct.But, once you've got
the problem isolated to the cylinder you can then
remove the head,
do a ridge ream and
remove the piston/rod out the top for a better inspection.
IMHO, that's about the best way to proceed.
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piston slap
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Noise only there when I start the jeep and gone after about a minute or two. The pistons have a coating on them that wears off over time causing the "knock". It doesn't sound like a lot of you have actually heard a rod knock. If
you can count really fast, a rod knock will make the sound about 120 times a minute. The piston slap about 750.

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flexplate bolts
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backed out a little and started hitting a spot on the top of the rotation. Nuts was all scuffed up (was not running long but could have deff messed a lot up) and a little bent.a manual trans and you cannot get to the flywheels bolts.
You would have to pull the trans. That is a common thing with auto cherokees. Sound:
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You can remove the "inspection cover" at the lower front end of the transmission and acces the bolts to tighten them. Just rotate the engine around and tighten one at a time as they come around
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If you have any info you would like me to add/edit post below! Also would like to get links to threads that fix said problems. I am shot as I have been looking at the forums all day so this will have to do for now...

TheMrCalcovaify is offline  
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4.0 , cherokee , engine , knock , noise

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