Ok, 400,000

my moneys on compression... How long do the rings last? as long as they see clean oil and are near flawless they can do another 400k... Id do a compression test... if it needs a new head gasket, no big deal.. the 4.0 is the "layer cake" of engines... Im sure it won't be as fresh as new motor but them i6s will go and go and go... 33s on 4:10 isn't perfect but its probably more manageable than some would think... I have 5:13 on 35s and honestly its almost too much gear. But that has been discussed about as many times as the sun has set in the sky...
Check your fuel pressure too, blockage there will result in some performance loss... clean out you TB and you'll see a lot more miles to come!

On a side note congrats on the 400,000 miles!

Don't give up on her just cuz she's old... make it to the 600,000 club and boast your millage status...
 
Just an update on the progress.....Vac test engine cold,idle speed,750+or-.
17" hg,with some needle wiggle.
Compression test.#1>#6= 150,175,160,185,175,170
IF I had the time to leave this XJ out of service,the head and timing set would have been repaired/replaced as necessary,,,,,but I don,t. So new engine it is..will be back on road again by Friday.
Thanks for your advise and well wishes.
I hope this helps others make the decision to keep on running their XJ,s.

Wayne
 
So basically you are a askhole? Those compression numbers are great especially for that mileage. That's a engine that will run for another 200,000 no problem, funny you'll trust a reman which has a known issue of never running as long as the original motor even though you have one that has proven the test of time and is still kicking strong...
 
So basically you are a askhole? Those compression numbers are great especially for that mileage. That's a engine that will run for another 200,000 no problem, funny you'll trust a reman which has a known issue of never running as long as the original motor even though you have one that has proven the test of time and is still kicking strong...

I am about to run a compression test on mine...just curious what is the percentage range the cylinders should be in. They always say 10% for outboards, didn't know what it was for autos.
 
It helps them quite a bit. All chains are gunna stretch

OK, got my new timing chain in this weekend. I had assisted with one about 5 years ago, and I forgot how much stuff you have to take off the front of the motor. It took me a while.
Mine was definitely bad, it had begun to rub on the cover near the crank sprocket. I only drove it to get me a well-deserved 6 pack, but the throttle response seemed better. I will know more once I get it on the freeway tomorrow.
 
I just had to post up again after my freeway drive this AM. What prompted me to change my timing chain is that I am approaching 300K on my 4.0 and it was getting sluggish. Specifically, not so much at WOT, but at freeway speeds, the Jeep did not want to accelerate without downshifting. The new timing chain is a dramatic difference at freeway speeds.....it now accelerates noticeably better without downshifting.

On a side note, the last oil change I did, I noticed some metal in the drain pan and I was concerned. I now have confirmation that it was the timing chain cover. Cool.
 
IF I had the time to leave this XJ out of service,the head and timing set would have been repaired/replaced as necessary,,,,,but I don,t.

Sort of hard to believe that his 400k XJ is a car he can't leave out of service. I guess this is his only car? Even if the engine was running great why think that anything else couldn't leave you stranded on the road. Sounds like it is time to find a new DD.
 
Sort of hard to believe that his 400k XJ is a car he can't leave out of service. I guess this is his only car? Even if the engine was running great why think that anything else couldn't leave you stranded on the road. Sounds like it is time to find a new DD.

You must be under the impression that everything on this XJ is the same age.
Only the motor has been untouched,
It is my only Jeep.
 
You must be under the impression that everything on this XJ is the same age.
Only the motor has been untouched,
It is my only Jeep.

Well sure I could assume that since I have only replaced a fuel pump, a radiator, and a ECU on my 92 which is still picking up highway trips every now and then with well over 200k miles. But it is a jeep so I don't pull out of the driveway thinking the car is 100% like it was off the lot.

That's also why it isn't my DD :D
 
I dunno but I'm sad to see a good tried and true engine get yanked and replaced with an engine with unknown mileage expectations. If it were me, I'd get the head redone and a new timing chain and gears and new lifters and be done with it.

And as a side note, I also was running 4.10's and 33" BFG KM2's and my engine only has 230,000 and had trouble keeping speeds. Since I went to 4.88's I don't have those problems anymore and only turn just over 2600 rpm at 70, and 2400 rpm at 65, not 3000+ rpm.

At 4000,000 I would see how far it would go and I would be proud of that engine! I would even slightly boast about it knowing that 99 percent of other manufacturers engines will never see those kind of miles. Just my opinion.
 
I dunno but I'm sad to see a good tried and true engine get yanked and replaced with an engine with unknown mileage expectations. If it were me, I'd get the head redone and a new timing chain and gears and new lifters and be done with it.

And as a side note, I also was running 4.10's and 33" BFG KM2's and my engine only has 230,000 and had trouble keeping speeds. Since I went to 4.88's I don't have those problems anymore and only turn just over 2600 rpm at 70, and 2400 rpm at 65, not 3000+ rpm.

At 4000,000 I would see how far it would go and I would be proud of that engine! I would even slightly boast about it knowing that 99 percent of other manufacturers engines will never see those kind of miles. Just my opinion.

I totally agree with everything you said....but as far as the original poster goes, I figure "Not my circus, not my monkeys". This thread has been really helpful for me though, considering I am getting close to 300K.

The timing chain replace was really beneficial...next step for me is to check compression. When the time comes, I will probably just opt to replace the head rather than a rebuild.
 
I totally agree with everything you said....but as far as the original poster goes, I figure "Not my circus, not my monkeys". This thread has been really helpful for me though, considering I am getting close to 300K.

The timing chain replace was really beneficial...next step for me is to check compression. When the time comes, I will probably just opt to replace the head rather than a rebuild.

Yes, I totally agree with you. I should have mentioned that, obviously, it's his toy and he can do with it as he pleases.

I am also thinking of replacing the timing set after reading this. Good info!!
 
I would measure the chain stretch before doing that job. Last time I checked at 160,000 there was no measurable stretch. A poorly maintained motor may have a lot while a well maintained motor may have no measurable wear.
 
Just my two cents,
I recently put a lotta dough into replacing a noisy motor thinking "hey, i love the jeep and its an investment". The new ATK 4.0's got more issues than the old one and altho if i can prove its the motor, fun, they'll replace it im still out a crap load of money... id give just about anything to redo that choice.
 
I finally ran a compression test this weekend...cold, dry. It was pretty much 150 across the board, plus or minus 5 at the most. Gave me some peace of mind considering I am nearing 300K.

BTW, 2000 XJ and I did overheat it pretty bad one time trying to get off a beach with a hole in my radiator.
 
I'm with the OP, better to replace on a driver, than to try for high-score mileage. Mine was at 300ish when I replaced with junkyard donor, with low compression in #1 cylinder, lots of valve train knocking, no power in a pull, etc. Replacing the engine and trans brought the jeep back to usable life. They arent trophy subaru for lesbians, they are jeeps, better to rollover and burnout than to be kept sitting for some stupid Internet fantasy galley.
 
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