Engine Help.....with pics

What's up ::? I'll try to make this as short as possible so I don't bore everyone.

A few months ago I picked up a 1997 XJ with a 4.0, AW4, 242, with around 150k on the clock for a very good price. Aside from the cracked block, the jeep is in very nice condition. I was given a 1998 4.0, AW4, 231 with 150k miles a few years ago for some work I did. I heard the 1998 run one time when it was delivered to my house but since then pulled the motor and everything else I wanted from the jeep and scrapped the rest.

The other day, I started tearing into the motor from the 1998 in hopes to put it in the 1997 I recently purchased. Since I dont know anything about the 1998 engine, I planned to replace intake/exhaust manifold gaskets, head gasket, oil pan gasket, valve cover gasket, RMS, FMS, HV oil pump, water pump, thermostat/thermostat gasket, o-rings from oil filter assembly, fuel injector o-rings, plugs/wires/cap/rotor, etc to freshen up the engine. When I started taking everything apart, I began to question whether I should keep this motor or not. I took some pictures of a few things and I was looking for input on what people suggest I should do.




When I pulled the valve cover and rockers, I noticed these rust rings around all of the pushrods. What could this be from? Something I should be concerned with?


The underside of the valve cover was very clean, however, there was some schmeg sitting here ontop of the head.


Most of the pushrods looked like this. All covered with what appears to be carbon deposits. Again, cause for concern?


This is the underside of the head. Lots of carbon build-up.


Shot of the block with the head off. Lots of build-up here also. The cylinder bores were actually very clean and not scuffed up at all.




All the head-bolts came out very clean except for these two. The threads are all messed up on one of them and there is a chunk in the other. Cause for concern??



I must admit that I got a little too excited to break out my new impact wrench and didnt clean the engine before I started to work on it. Some of the debris seen in the photos is from all the schmeg on the outside of the motor. How would you recommend I clean the motor now that everything is removed from it??

Please let me know what you think I should do with this motor. I dont mind doing the work to this engine if everyone thinks its a good idea. If you think this motor has seen too much abuse, please let me know and I will consider other options. I would really like to build a stroker but I just cant afford it right now. On sunday, I am going to look at a 4.0L from a 1999 Cherokee with 120k on it. If you think this would be a better idea, let me know.

Thanks for all the help.

engine looks fine to me. some carbon build up and some surface rust from not running for a while. the smeg is nothing compared to what was in my 89 when i pulled the valve cover.

as for wear, you need to break the engine down, measure and check the tolerances.

either swap the long block in and take your chances or take it to a machine shop and have them break it down, check for wear and cracks, and rebuild/machine what needs to be done.

i don't really know anything about rebuilding engines, but i've torn a few down. that doesn't look too dirty. like 89xj said, tear it down and check for tolerances

if everything is ok, it's pretty easy to make a cheap parts cleaner. with waterproof tank, some scrap metal, bailing wire, a manual car charger and some washing soda.

there was a link on pirate about it...

i don't see why that wouldn't be a good way to clean everything fairly easily...

For 150k, that is a clean engine... I would remove the carbon from the head and basically call it a day. Won't hurt to put a new oil pump in but remember these inlines are known to run a quarter million miles and more if treated well and from looking at the lower end, this engine had regular oil changes. I have seen lower ends that are pitch black yours still looks like oil.

Right now, the rings are seated, if you pull the pistons to re-ring, you will have to hone the cylinders which will open them up and give you a poorer seal than you have now. The junk on the pushrods is normal build up and again, for the miles they are clean. The rings you are seeing are from the engine sitting and having some time to rust. Clean them and reuse.

Given the color of the oil, I would not replace the bearings.

You will need new head bolts as they should not be reused.

Now would be a good time to replace the stock exhaust manifold as if it is not cracked it will be...


Remember that you need a torque wrench to assemble the engine.

Just my .02...

Wish my 94 looked that good inside !

Glad the engine is in decent shape for the miles. What should I clean the head with that won't negatively affect the valves and seals?? How about the block? I assume blow all debris sitting on top of cylinders from removing the head with air but how should I actually clean the top of the cylinders?? How about the pushrods?? I would like to clean the outside of the block also so I don't have a chance of messing up the head gasket but I'm thinking that may be best left for after the head is installed. I don't wanna get stuff down in the cylinders.

Just another thought... I never use compressed air to clean as you never know just where the junk is going to go. Vacuums are your best best. I would rotate the engine to bring each piston up the TDC before cleaning. You could use shop rags moistened not dripping with solvent to get the carbon out As it is apart, I would commit to a new set of valve seals and have the head tanked at a shop. Most shops will do all of the assembly for you for a nominal charge. Have the valves reseated just to be sure as well as checking the head to make sure it is still flat and the guides are good. Solvent for the pusrods, pick one you like. It is important that they be able to flow oil. Cleaning the block may have to wait until it is back together. Basic rule is that you clean your way into a project... You cannot reuse the head gasket.

Just rebuilt the top end on my 89. Ideally, always check compression before you tear the head off, but since it is a 98, I wouldn't think there would be much issue. I spent about $280 in getting all seals and freshening it up. While you have the engine out, go ahead and replace the freeze plugs, there's 5 down the side, and one on the back of the head. I took my head to my local machine shop who sees me a lot, while I get a commercial discount, normally they charge around $100. They'll clean it, clean and reseat the valves, install the valve seals, and pressure check it to ensure its not warped and there are no leaks. Do any modifications you want done to it while its out, makes it much easier. Take a look at your engine mounts. Factory ones are $38 from Quadratec, or you can go with the Brown Dog Offroad HD ones for just under $100. Not sure how the temperature is up there in the summer, but down here in the summer while on the trails, I sometimes get near overheating. I spent the extra and replaced the factory pump with a highflow, and believe me...it works. Maybe a little to well in the winter, I have to make a grille block this weekend to screw on to take away some flow to the radiator. Times 2 on the shop vac for cleaning the cylinders out. I personally would do, water pump, freeze plugs, motor mounts(if bad), oil pump, and grab a head gasket set, includes all you'll need except for the exhaust donut gasket. While uncertain about my engine's history, it appears to have had new rings and pistons installed, acts as if its cammed, and dont have any problems with oil reaching the top. I have 232k miles on mine. If these things are taken care of, they'll keep going and going and going.

I agree with everything he just said but I think it would be foolish to not replace the motor mounts even if the look ok, they are so prone to failure and the engine is already out, just go ahead and replace them.

Sorry about that.. Old habits and all... Motor and Transmission mount renewal are, usually, common practice when replacing the driveline. Didn't think to say it.