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time to dig out the warranty papers..


nobody of any consequence
ok i think the 4.0l in my 99 is going bad.. the rapping it is making is not constant though...its the strangest thing.. early morning start-up= no noise at all... fully warmed-up engine = no noticable noise... when i hear the noise is when i go out and start it at lunch and when i leave to go home. about 4 hrs of cooling.. engine temp around 110 or so.. sounds like a random rapping... not a steady noise like vavle clatter.. seems to go away when fully warm.. has gotten steadily louder over 2 months... oil pressure is good(at least my gauge thinks so) never run low or overdue on maintenance intervals.. sounds like piston slap almost.. but it isnt there with a cold engine.. thats what has me confused.... i'm afraid i'm in for a fight over engine replacement.. maybe it'll nuke in the next few days. then there wont be any issue about the condition internally..
any thoughts????
almost forgot.. it just turned 73000 miles..
I am dealing with a bit of what you are talking about in my '98 4.0. Is an inconsistent slight 'rapping' sound. Do not believe it to be a rod knock or wrist pin or anything like that however. These 4.0s have a history of piston slap and went so far as to use more expensive carbon imbedded skirts on the pistons and tighter clearances to combat the noise in the later models. The success may have been dubious. Would be great to never hear any abnormal sounds out there, but do not think is anything to worry about in your case.

If were a rod knock, would be pretty much heard after warmed up every time. Before long would show up on the oil pressure gauge. Wrist pin problems are quite rare.

If there stands a chance that a dealer will do a warranty, well then most assuredly do so!! I'd bet that chance is slim-
Did you buy your Jeep new or did it have a previous owner? I see you also have an '87 so you should be use to all the noise, vibration and harshness of the 4.0. I thought the newer engines were designed to eliminate those nasty things associated with the older ones. Did you change anything recently like the type of oil or filter you normally use? On the other hand it may just be a Jeep thing and you'll either understand or be miserable. I hope it turns out for the good.
i bought the 99 from a stealership in november last year.. it was a previous lease. no noise until recently. and the 87 runs as quiet as the 99 now that i tightened the flexplate and replaced the growling p/s pump.. i will be on the phone with the service dept today.
Has it made the noise while you had the hood open? i.e. not moving? The reason I ask is I had some rapping on mine though I was pretty certain it was not the motor and finally deduced that the motor mounts were bad. Just a thought.
i will check them out.. just to cover all my bases. the dealer got an earfull today and im takin it to them on monday..
well it went off to the service dept. today.... they said "yup.. its got an engine noise" they also said " the warranty co. wants service records and receipts" since i do all my maintenance...DOH!!!!!!!!! nowit's time to dig thru the receipt box and find 5 or 6 filter receipts and oil... they reserve the right to withhold any decision on coverage until its pulled apart.. great.. service manager is suggesting a short-block... he said it would be around $4000 if i foot the bill myself... great. i'm crossing my fingers that this doesnt drag out and become expensive.. it's supposed to drag me to Moab next month!!
ok... my ranting has subsided for now.... anyone get any warranty work done like this and what headacvhes did you run into??
i find out today if they are going to cover a new short block... i've been sitting on the edge of my seat since yesterday morning... unless the engine is a "bad core" from the factory which is doudtfull, i apparently bought 57ooo miles worth of someone elses neglect... wonderful.. i think it's time for a new Jeep if they dont cover me..
My parents Buick was new last summer with only 15,000 miles. Tick tick in the engine. They wanted service records from my dad, he does his as well. They replaced the engine because of the warranty, and the fact that it was cheaper than a rebuild. Now he did fight them a little on that but it worked out great in the end. He traded it in a month later for a new one. But wait and see what they do first. Juice
now i'm waiting for an adjuster to come look at the engine... it's in pieces and i still dont kniow who is going to pay for it!! to my benefit there is no sludge buildup, but it looks like the head had been overheated once cause a few of the combustion chambers are "blued" and a little discolored..
now we sit and wait..
I went through a very similar experience almost a year ago...

Difference is I had my block heater fall out on the highway, ended up overheating pretty much everything.
Took it to the dealer with hopes that the ext warranty would cover the fix, turns out "block heaters" are not one of the covered components listed in the warranty papers. This was discovered after about a week of "we need service records" ( faxed them 20 some odd pages of walmart recepts :) ) and we need to wait for the adjuster etc etc...

They claimed it needed new pistons and rings, and a head job. Were wanting in the neighborhood of $2500 to do it.

I paid them for the tear down time, loaded the jeep on a trailer and took it home.

Long story short, I somehow got talked into stroking it, finally got around to working on it in march and had the stroker running beginning of June. I'm still fine tuning, but it's nice to have the jeep running again.

In retrospect, since it's my daily driver, I should have just bought a low milage used 4.0 ( found a '98 with 30K for $1200. should have done that..) and just swapped that in... The stroker has just had more issues than a swap would have had.

Oh and after all was said and done, the damage was way more than pistons and a head job, add a warpped head, cracked block ( yes, I cracked a 4.0...) bearings etc.

I'm probably out about the same amount as I would have been had I had the dealer do the work. But I know it was done right ( would have been back in the dealer the next day with that cracked block...) and I ended up with gobs more torque than it had stock....
Sorry for the long reply.
Just sharing my experience. Not a big fan of extended warranties any more...
thanks for the input adam..... i am still waiting.. the adjuster is coming tuesday a.m. and he wanted 2 pistons pulled out.. so this thing is in 10,000 pieces and i am having thoughts about how well it'll run if i tell them to slap it back together till i can do it.. i am learning alot about warrantys thru this.... if it is not covered i'm trading it in for a new wrangler.... i know , i know!! i'd rather take a 3000 hit in the pocket with a brand new vehicle than on the credit cards to do it in my driveway... now my weekend is gonna suck because i cant stand waiting..
I would think the moly coating came off of the piston. I work at a dealership as a tech and I have seen a few engine problems with the moly coating. We recently had a 04 WJ 4.0l come off the truck with a knock noise, bad piston. We had a 3.7l KJ motor with the moly coating coming loose and causing a knock noise very similar to what you are describing. Cold start, no noise, warm start, lots of noise, with no noticeable noise in between. I think they are right about the source of your noise.

Good luck with the adjuster for your warranty. Most are reasonable people, but every once in a while you get a real jerk that thinks it is his money he is spending and not the warr. co. money.

BTW, Chrysler warranties may be a little more expensive but are well worth the extra money, they don't have adjusters to approve the repairs, and usually cover more items on your vehicle. Also some extended warranties will not cover fluids or miscellaneous supplies such as silicone sealer, parts wash and even engine oil or coolant.

Have fun, and keep your Cherokee.

WOO HOO!!!!! guess who's getting a new long block for an early x-mas present?? thats right! cylinders #1 and #2 were worn out of round by .004 and .0075 respectivly.. the rep who looked at it wanted to check it himself i guess they dont even trust an ASE cert. technician these days.. i thought it was piston slap but thanks for all the hints and ideas guys. i should have it back by the end of the week... just in time to put my lift in. and that means... I'M GOING TO MOAB!!!!!!!!!!!!!!!!!!!!!!
can't think of a better shakedown run for a new engine..
i finally picked it up today.. Mopar re-con long block in place... prety harsh vibration at idle now.. runs like a #$%^& now though.. never had this much power before..(maybe a tell-tale sign of early wear..)... i opened the hood and i didnt recognize anything... at first i thought they swapped it with a scrap yard engine with all the accesories.. i attribute this to never spending much time under the hood of the d/d because it didnt need much attention.. where as i am constsntly under the hood of the trail rig... did a 20 mins trip up the highway and back home... first thing i found was my accesory belt shredded ..... it seems the tech (read: ASSHAT) who installed it didnt think he needed to line up the serp belt with all the grooves on the a/c pulley... just 3 of them.. i had 12" long shreds wrapped in the fan and all over the place... i drove directly back to the shop and drove it right into the service bay (they didnt like this) this was 15 mins before closing time.. they said they couldnt do it today.. I DONT THINK SO!!!! needless to say they did it for me.... the only real issue i have now is the starter makes a "squeeking/squueeling" sound for a second just as the engine fires up and over powers the starter... he tells me they dont "shim" these starters like chevys do, for proper gear mesh... i'm thinking its something to do with the wear pattern on my starter not matching the wear pattern on the flexplate... i can imagine premature wear if thats the case... he knows its coming back to him on tuesday if it doesnt clear up... no noise when he got it, no noise when i get it back...
thanks for letting me rant guys..