Replacing Head Gasket 2002 Sahara 4.0

2002Sahara4.0

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Hello all. Excited to be on a TJ specific forum.

I am replacing the head gasket on my 2002 Sahara. It has 130,000 and has run strong up until a traffic overheat and now a misfire in cyl. 1 w/ code. I changed plugs, O2 sensors and checked coil rail and injectors. I cleaned the engine, ran it a couple of days, and checked and noticed a seep leak on the engine case on passenger side cyl. 1. I also have the intermittent strong smell of gasoline and steaming coolant at various times under load.

I have rebuilt engines before, but never on a jeep, so I am asking this forum for help in anticipating any bumps in the road or other things I should be looking at while I have the engine opened. Also, not sure what the PO did, so I was wondering how to identify if this head is the infamous crack prone 0331 or if it has been replaced.

My plan is to purchase the Fel-Pro gasket kit, the head bolts, thermostat and the exhaust gaskets. I pulled the valve cover and injectors off and the rockers and springs look good.

Should I replace the fuel injectors since I'm doing this? Water pump? Lifters? What kinds of maintenance things should I do?

There should be a picture at the bottom of this post. Really appreciate all the help.!! Thanks for the advice and best wishes in your adventures!!

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Well there are two 0331 heads. There is the crack-prone version which is just the plain head, used primarily on 00-01 4.0s. Not all of them crack, but a lot do. Most, if not all of the 2002s came with the upgraded (TUPY) head style. The way to check if yours had the newer style is between #3 & #4, there will be TUPY spelled out on the head. If yours doesn't have TUPY on it, you may have the crack. So, look between 3&4.
 
If money isn't an option I know you can get reasonably cheap crate engines for these things. I'm talking about engines that are 100% rebuilt and fully assembled for usually around $2000 or less. I only throw that out there because at that price it often times makes more sense to buy the crate engine and just throw it in as oppose to rebuilding your engine yourself.

If your engine only has 130k miles I would replace all the gaskets, get your fuel injectors cleaned, etc. I would get a factory service manual and go through it with fine detail making sure to check the tolerances of everything upon reassembly. Most of the parts for these engines (i.e. lifters) are so cheap, that it makes more sense to buy new ones as oppose to re-use the old ones.

If this was an expensive engine like one in a modern BMW, then you'd want to re-use anything that could still be used. However, these 4.0s are a dime a dozen, and therefore very cheap to rebuild and maintain.
 
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Cool. Thanks for the info. I'm planning to slowly and methodically rebuild this engine. I considered swapping a new engine, but everything else is working strong. Once I check everything, I was planning on replacing all the inexpensive stuff (lifters and some hoses and such). I figured this is my opportunity for a learning experience.

I keep finding little gifts from the PO. I saw a wire out of place, followed it around and found a cold weather heating pad on the oil pan and under the battery, all connected with an outdoor grade 4" multi-port extension cord. PO had that thing in there nice and neat. Was hard to tell it didn't belong. So, Im sure I will be replacing a few random parts as I get deeper into this project. Gonna be fun!

Thanks for the help!
 
The nice thing about it is that 130k miles on a 4.0 is basically nothing. These things can run for 500k miles without any internal part replacement from what I've seen.

That being said, you most likely won't have anything in there that's very worn (assuming the engine was reasonably well taken care of).

Speaking of previous owners, check out this thread I started that is right on topic with what you're speaking of:
What's the weirdest thing the previous owner left in your car?
 
Quick update. Been slowly and methodically taking the top of this engine apart. Here are some pics. Any comments are greatly appreciated.

So the first set of pics is the intake. Looks so grimy. When I bought the car it had the stock air box, and I have not changed it. Why is there so much crap getting in there? Bad gas?

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had to continue on another post to ad more pics.

These pics are of the ports. Cyl. 1 is the misfire port.

So, what brand cleaning product should I use to remove all the junk off the intake?

And. Is there a trick to removing the head bolts, or is it controlled brute force? Even though I got new ones for the install, I just don't want to snap any or cause any damage. I usually use my Milwaukee impact.

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The grimy-ness, is just carbon. It looks nasty but it'll happen over time, regardless of what air intake or filter you have. That's why we have to periodically clean out the IAC valve to get our Jeeps to idle normal once they get dirty with carbon. You can get a good amount of that gone by using throttle body cleaner. 3M supposedly makes a great throttle body cleaner called "system intake cleaner" but I haven't found it by itself anywhere, at any of the different parts stores I've looked at or Amazon without it being in a kit that requires a special spray nozzle. I just use CRC from O'Reilly and it seems to work reasonably well.

Due to how dirty everything is, I would take off your IAC ( the sensor on the throttle body at the very bottom of the picture of your throttle body, it's cropped out of the pic) and take it off and give it a good cleaning (with throttle body cleaner) and also clean out the inside of the IAC housing inside the hope throttle body cleaner and an old tooth brush or whatever you can get in there to scrub it clean. Probably wouldn't hurt at least.

The head bolts should be on there by 100 ft pounds on the very front drive side bolt, and 110 on the rest, if I'm not mistaken. I would just use a breaker bar and whatever socket you need and take them off. They're pretty heavy duty bolts which I believe are grade 10.
 
OK. Head is off. Below are the pics. All that liquid on the deck (coolant, it seems) was internal. The outside of the engine was dry. The liquid got shook-out of the head as I was pulling it out.

I took a photo of the valves. When you experienced guys see that, what's your reaction? The spark plugs, I should have taken a photo, looked brand new except for the one. The plug was just as black as the valves.

Interestingly, or maybe not to you all, the top of the piston of the corresponding cylinder didn't have any more carbon build up than the other five, but the valves were distinctly different. Is there an explanation for that?

Thanks in advance.

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not sure why nobody replied and I know it's long past but for anyone who stumbles across this thread in the future, it looks like you had coolant leaking into all cylinders except the one. (the black one)