2001 TJ 4.0
lower engine knock on start up last about 4 minutes, then quiet untill next cold start up,
engine has no oil leaks, no oil usage, no roughness, runs great. runs quiet at 65mph
any thoughts, really sounds like a rod or piston noise, but on does it on start up only
is it time for a engine????
just drive me nuts when started
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so basically after the oil is warm the noise goes away, could be valvetrain noise, loose rocker or something, i noticed jeeps are noisy at first when its cold till oil gets in all the crevisis.
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Not a lifter, from the bottom end
and its loud, it drives me nuts, if it was a rod wouldn't do it all times.
confused, don't know what to do. drive it until it comes apart?
can get my hands on a low mileage 4.0. need someone to install it.I don't havce a place to install it but will help -
possibly just an exhaust leak??? know they can trick even a well trained ear, and can disappear after parts warm up (swell)...
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Could be a whats called a piston slap. when piston is cold it is loose in the bore and tends to rock more creating a knocking noise. would suggest either replacement of engine or find out what cylinder is the problem and see about getting a slightly oversized slug. when i say slightly i mean less then .010 this way an over bore will not be necessary. usually can find pistons that have a teflon like coating on the skirts this is good enough.
have see a few 4.0L do this but have seen many more GM 3100 do it. just some info. hard to diag over the internet. -
Wouldn't a compression check on each cylinder determine which piston was slapping? Would over size rings fix the problem?
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Not all the time does a compression test determine the affected cylinder. Since it is usually the piston skirt that is the problem area. oversized rings wont fix it.
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That's what it sounds like, as the engine warms up and internal parts expand noise goes away.it has been doing this for over a year, colder it is outside louder the noise becomes. I found a used complete 4.0 50k from a 2002 Tj.. drove it before engine was pulled last wkend. even did a surpise visit on Sunday to start it cold,no problems.
going to take it, looking for someone to install it and how much$$$ -
Post a location so people can narrow down their suggestions.
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PM'd
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I'm in the Annapolis area, but can bring jeep to you.
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id run the current engine till she blows up.
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x2
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Mine has 40,000 miles and knocks when its cold. Then when its warn its gone. Only lasts for a few mins.
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the most likely possibilities the pistons on the 2.5 and the 4.0 come with a teflon coating that can wear away especially if it ever overheated and usually is just an annoyance and not threatening but they also wear out rod and or main bearings.which you can usually pick up with lower oil pressure when warm.either way you need to pull the pan for inspection.you can see the bottom of the piston skirts from through the pan and ck the rod and mains while your there.very easy job on a wrangler
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Been there, done that.....check in your oil pan when its off. That where I found my piston skirt after we swapped the bearings.
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