What tends to go bad first on an engine?

[ATex7239]

Seals/gaskets and electronic components always seem to get me before anything. Never lost an engine though.

 

[adventureboss]

Is your Jeep a 2000 or 2001? Some 4.0 engines in those years came with a defective casting that resulted in cracked heads.

About your question, I would say in a typical engine that's adequately maintained, the rings are what wears out first.

Mine is an 06 so luckily I dodged the crack prone heads, but I had to replace mine early anyways. When I first bought it, it used to run quite hot, like 250+ coolant temp. Of course the temp gauge was buffered and would stay pretty much centered at 210. I don't think the previous owners ever took care of the cooling system

Hopefully I have a good amount of life left after replacing the head.

 

[Chris142]

Mine is an 06 so luckily I dodged the crack prone heads, but I had to replace mine early anyways. When I first bought it, it used to run quite hot, like 250+ coolant temp. Of course the temp gauge was buffered and would stay pretty much centered at 210. I don't think the previous owners ever took care of the cooling system

Hopefully I have a good amount of life left after replacing the head.

If it's the 4.0 it is overdue for a cam. The 05-06 opda eats the cam gear.

 

[Escape08]

timing chain or timing belt

 

[Fabulous50s]

Well if it's a 5 year old Dodge then it may eat a cam (or 2, or 3 or 4) before 100k

Or if it's a 10 year old Honda it may eat a valve due to excess oil consumption at 180k

If it's a 65 year old Ford you may just pull the engine to freshen it up and some paint.

These are just my own personal experiences.

Back when I worked on vehicles professionally I'd have a lot more pictures.