Hi everyone. Last year I purchased a 1996 Jeep Cherokee with the 4.0 liter Inline 6 with 186,000 miles. Today I decided to pull one of the spark plugs and look into the cylinder just to check out the condition of everything, and it looked really clean. So, I’m trying to figure out if this engine has been rebuilt before just judging by the condition of the cylinder walls and the cylinder. The Jeep has had 7 previous owners, yes, 7. So I’m assuming maybe one of them had rebuilt the engine and never left any records of it. Here’s the photos below. If anyone has any opinions on the condition of the engine I would be interested on hearing your opinions. There are no tags or anything on the engine indicating that it’s been rebuilt, though there is a mark on the side of the engine that I believe says 7, looks like it was written using a paint pen. Anyways, thanks for any opinions!

EDIT- Whats written on the side of the block is “d”. I don’t know what this stands for but I don’t think it’s there from factory, I could be wrong though. It’s on the passenger side written in paint or something.

 

I still can see some cross hash marks . what does the engine run like and how the oil pressure ?

 

Engine seems to run pretty well. Though I’ve never really heard another 4.0 so I don’t have much to base it off of. Oil pressure is about 40 after its fully warmed up.

 

Looks to me like it's been steam cleaned recently.

I also wonder if it's had a head gasket or head replaced at some time in the past. Take a look at the first picture. See that interesting geometric pattern in a line around the cylinder wall? That was left by the oil ring. I have seen that a few times with engines that blew a head or head gasket and it sat for a bit with the coolant in the head. It rusts an imprint of the oil ring onto the cylinder wall.

 

Sounds like it's good I would just take good care of it and run it . one of the biggest problems is oil pressure and yours is good .