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1999 4.0 engine life ?

S

scotttruhart

NAXJA Forum User
Location
las vegas
HI

Have a 99 sport i bought new and have put 90k on. I have heard that the 4.0 is "bomb" proof and should last very long time. Im at the point where the jeep needs a lot of work like shocks etc.. the body is perfect as imin las vegas so no winters to rot it away. i hate to put money in car if the motor only lasts a bit more. engine seems to be perfect and really shows no sign of oil consumption etc.. i have used mobil 1 every 3 k since brand new.

any clue on how long these motors last? oh also its auto tranny and has had fluid changed 3 times and shifts fine.. are these trannys prone to failure or are they long lasting??? , i would say that i drive it normal not babied but just normal use to work etc..
thanks
 
The 4.0L lasts and lasts...200,000+ is common with semi-religious care.
The AW-4 is just about as good; they hold up well to high torque and horsepower from the 4.0L and stroked engines.

You've got a good combo there.
 
Answer for both: A damn long time if taken care of.

Of course my motor sounds like its going to blow up within the next five minutes if left to idle but...and I'm knocking on wood while saying this...I've never been left on the side of the road by my XJ (also its a 5 speed) I have owned it for almost 5 years and put 60+ kmiles on it. Its at 155K.
 
I had an 88 XJ with 190,000 miles on it when it started to die. It was close to throwing a rod and I tired to make it go with no luck. I sold it, the guy that bought it drove it home and then to his shop with out the engine dying compleately. It never once did leave me stranded though. I took it to a couple of shops and they told me the Jeep should not be running. I am on my second XJ now, and the engine is a tank if you take care of it. I have never had a problem with the tranny.
 
I plan on 500,000+ on my 98, mobil-1 since 5,000mi breakin, mobil-1, mopar and K&N filters, plus mobil-1 lube in the AX15, NP231 and front d30, drydene in the rear since I put the auburn LSD in two years ago.
Take care of it, flush the cooling system yearly, watch your gauges and fix problems before they cause more problems and it should last a long long time.
At 90,000 it's just broken in :D
 
110,000+ on my wife's and it runs like a top. These motors will EASILY go 200,000+ with regular maintenance. It's sounds like you are in a similar situation as me as I am starting to replace exhaust and shocks etc. I plan on driving this thing in to the ground and then rebuilding/building it for the off-road only once my wife get's a new vehicle.
 
I've got over 225k on my 94. I did the lower end (bearings, oil pump, etc.) when I had it out a couple of years ago, but it really wasn't necessary. I wouldn't have done it if the engine wasn't already coming out for other reasons.

Someone I used to work with had a 94 with over 300k before it got t-boned in 1999. Aside from regular oil changes, ZERO maintenance to the engine and still going strong.
 
GREAT motor! I have 130,000 on my 99 Classic and it still runs like a top also.
40 lbs oil pressure at idle (55 to 60 lbs at hiway speed)
never gets over 215 deg
have ALWAYS ran Castrol GTX 20/50
Fram filters (sorry guys)

Only things I have had to replace are....
serptine belt
water pump (at less than 40,000
oth26.gif
)
oil sender (last week)
And regular maint.
Look.gif
to include tires & brakes
 
It lasts forever and can be moved from vehicle to vehicle. I change the roll of toilet paper about every 1000 miles and add a half quart of oil. Since breakin, I have never done a full oil change. The oil is so clear it is sometimes hard to read it on the dip stick. I sent off a sample to have it analytically tested and got a phone call asking if it was a joke. The oil tested better than out of the can.
 
I have a 99 and 13osomethingK, and the only problem is a little wet spot that seems to be coming from the valve cover gasket.
My brother in law owns a garage and he told me that the problem with the 4.0L engines is not wear and tear, but the numerous leaks that they develop between the 160 and 180k intervals
 
They don't leak, they mark their territory.

Personally, most engines develop leaks after 100k miles. The 4.0L is no different, other than more of them make it that far.
 
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