Just replaced my cylinder head at 191k miles because of an exhaust valve not sealing correctly and causing a misfire at idle. I still have 170ish psi on all cylinders. I'm wondering how much life I have left in the motor. What typically fails first on an AMC 4.0? Is it the piston rings? Valve seats? Curious what actually fails when people finally condemn these motors at 300k, 400k, whatever the mileage may be.
What goes first on a 4.0?
- Thread starter adventureboss
- Start date
DeltaNu1142
TJ Enthusiast
I expect to run out of money long before I hit 250k.
BathiasRei
Member
From what I've seen and watched online, the 4.0L lives forever but can sometimes succumb to piston problems (post 1996 I believe?). Usually cracking off due to aluminum pistons in an iron block and long years of heat cycles. Have also heard about lifter issues eating cams but that seems 1 in a million.
BathiasRei
Member
Rolling in new bearings is cheap, easy and fast
Piston slap sometimes gets folks
Look up DexJs on YouTube...some great no nonsense videos on the 4.0.
-Mac
Piston slap sometimes gets folks
Look up DexJs on YouTube...some great no nonsense videos on the 4.0.
-Mac
I've only had 18 Jeeps with the 4.0 engine. Nothing has ever gone wrong with the engines (knock on wood). Nothing went wrong with my 2.5 with 250,000 miles either.
WestCoastDan
TJ Addict
That RMS is the biggest 'problem' in ours.
I always say that I'll have that fixed when the engine needs to be rebuilt, until then it just gets topped off pretty regularly.
But by adding a fresh quart of oil every 3 months and replacing the WIX filter every year, this damned thing will probably never die.
I always say that I'll have that fixed when the engine needs to be rebuilt, until then it just gets topped off pretty regularly.
But by adding a fresh quart of oil every 3 months and replacing the WIX filter every year, this damned thing will probably never die.
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