New to my XJ & wrenching - How to choose parts and what to prioritize?!

[myXJpeg]

***TLDR***- new to all of this. Was told I should come here from my previously misplaced thread.

1999 SE, 4.0, 4x4, basic interior everything except cruise control, no missing parts or aftermarket mods, 39,500 miles, former university campus truck. That said, this XJ will surely outlive me at this point when I am done restoring it so...

Is there a thread or 5 that someone can point me to about how to know what parts are reliable and basic maintenance process/order of operations on the XJ in general? Where do I start?

With the intent on staying mostly stock, what is worth good $money$ and what is ok to be ˘heaper on - my main concern is simply what part/brands can I trust? Quality over price is my general go to for OEM or slightly better than OEM parts. Definitely want to avoid junk that fails quickly or often. My plan at the moment can be seen below.

Digging through various XJ forums is an endless mess of opinions and outdated info for parts that often no longer exist, it seems. I can search all the terms (and have) but the words "thermostat", "radiator", or "O2 sesnsor" for instance come up a lot. It is a lot to wade through. Mine needs new fluids and, mostly, TLC for wear parts and cosmetics as best I can tell.

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***Full version***
This has become long, very sorry.

I am super new to wrenching and XJs, my plan is to do most of the work myself -- 1999 SE 4x4, 4.0, all the skid plates, fully manual/basic interior, no mods/all stock, 39,500 miles. Built 10/98 and I have the build sheet. So far it seems like a straightforward elbow grease + youtube project.

The intent is a mostly stock (upcountry style lift + bigger tires eventually) camping/errands and trail head reaching kind of vehicle, not a daily driver, and I never intend to go wheeling or mudding. I have come to realize since I bought it that these are hard to find in the overall condition, unmodified, that mine is in.

So, it surely has more engine hours than miles since it was a university campus vehicle in Texas, but that is not verifiable. Some guy likely sat in it a lot with the AC on but no way to know at all how it was used. It was assigned to campus food services director at one point for a long time, with low use from the milage tracker left in the glove box. And later to food services pest control but with much less consistent tracking. It sat for most of 2020/2021 unused which is probably what made them surplus it in 2022... we all know sitting unused is not good. Incredibly and most crucially it has NO problematic rust. None that I can find on the frame and only surface level stuff on replaceable parts. I have not pulled the carpets yet so there could be some hiding in a floor pan but it was parked under cover for its whole life, too. No salt on the roads here, either.

My main question -- How do you tell what OEM or slightly upgraded OEM parts are the go-to for any given item?... even with tons of searching forums it just seems like too much to sort through with so little experience!

Now I look at parts and there are so many options for everything (pros and cons, right?) but the hard part is these options come with endless opinions... they vary from cheap parts claiming "NeVeR uSe ThAt PaRt!!11!!!" to "I used it and it is great," to many items just not having reviews or being obvious low cost junk. But MOPAR parts seem to be, usually, a rip off, too?! Except maybe the thermostat from Chrysler? Autozone/ORielly doesn't seem great, either, for some items but not all? 23.5 year old vehicle just means lower quality parts now?

I HAD MECHANIC - replace valve cover gasket (misstated as head gasket in a previous post) + fresh oil change + serviced rear diff w/ full synth to get it into workable order before I dove in.

I COMPLETED - installed new fan shroud, big 7 wires and headlight harness upgrade.

It runs pretty good, fires up reliably but with occasional grinding sound if its cold every 3rd or 4th start. It has intermittent rough idle (having no tach is annoying) and gets REALLY bad mpg for how stock it is on 215/15 tires and driving it gently. 11mpg highway & 10ish city. It overheated on a hot day in stop & go with AC on once (It is Texas, so this is common and can't happen). Haven't had any leaks since aside from maybe a half-dollar sized tranny fluid leak over the course of 3 months or so. Watching that one carefully. ... but general maintenance should help these a lot?

I drive it once a week at the moment to keep stuff moving/lubricated since the overheat until I get it into better condition. Has not overheated since and I made sure coolant levels were proper.


***I THINK MY XJ NEEDS***
#1 full coolant system power flush (badly needed), absolutely job #1 in my mind
#2 full tune up (plugs, wires, distributor rotor/cap), more?
#3 a rad cap, 195 thermostat/housing/gasket, maybe a water pump? It has new
ish radiator with only 6000 miles since 2017 but maybe it should go?
#4 clean the injectors and throttle body. This should help MPG a lot?
#5 transfer case, transmission, power steering and brake services?
#6 clean the engine bay to see what may be going on more clearly?
#7 should probably replace a few sensors, too. Not sure which ones are reliable
and which ones wear out more easily? O2 and TPS? IAT?
#8 less important is the suspension. Leaf springs are flat,
front coils are so-so, shocks are worn out for sure. But engine first.
#9 grease joints and replace any rubber mounts/stops that need replacing. None are too bad but all are 24 years old.
#10 get rid of basic, idiot light dash cluster, get a tach + actual temp and oil gauges. This would help me diagnose some things on the fly
#11 Needs headliner replaced and a damn radio and speakers. All dead. Got a new OEM head unit from a Reddit CherokeeXJ member though. Would love to add overhead console and back upper speakers.

Is this a good list and good order? It will all take time, not looking for it to be done ASAP.

***ALSO*** --
Thanks to for being a great learning resource for the last 5 months so far though! I knew nothing about engines to learning the layout and functions of everything really quickly because of y'all.

[myXJpeg]

Also auto AX4 paired to 231 and the8.25 w 3.55 gears

[Anak]

One thought on the overheating: You may need a new fan clutch.

Some folks will swap in a ZJ clutch. Potential downside of that is the fact that the ZJ clutch gets closer to your radiator. Worn motor mounts or the addition of a heavy duty (thicker) radiator may lead to interference issues. I am currently running a Duralast 922625 fan clutch (intended for an XJ, heavier duty than the original design) and it seems to be working well.

[lawsoncl]

I would not blindly replace sensors unless you have good reason to suspect they're bad. The new aftermarket parts tend to be poor quality versus the oem ones.

[myXJpeg]

Originally Posted by Anak

One thought on the overheating: You may need a new fan clutch.

Some folks will swap in a ZJ clutch. Potential downside of that is the fact that the ZJ clutch gets closer to your radiator. Worn motor mounts or the addition of a heavy duty (thicker) radiator may lead to interference issues. I am currently running a Duralast 922625 fan clutch (intended for an XJ, heavier duty than the original design) and it seems to be working well.

Since I only have idiot lights and cant watch the temp, how does one test their fan clutch to see if it is a problem? Bluetooth OBDII + an app to watch the data/use digital gauges?

Would happily do a replacement fan if needed, XJ model is fine by me.

And I 100% know a coolant flush has to happen as the coolant is rust colored. Could be a mix of coolants, definitely old, etc. The Spectra radiator (plastic tanks) is super new so I am not going to throw that out unless the flush and other parts don't help!

[myXJpeg]

Originally Posted by lawsoncl

I would not blindly replace sensors unless you have good reason to suspect they're bad. The new aftermarket parts tend to be poor quality versus the oem ones.

That makes good sense. Thanks.

Are there typical MPG-related problem-child sensors that pop up regularly on the XJ vs. other vehicles? They are maybe not throwing a code but maybe could get cleaned? I think most of the sensors on the throttle body qualify for this probably and I badly need to clean it along with the injectors. Or usual suspect and dont worry about it?

I know my rear O2 sensor is on about the only rusted part on the whole jeep. Maybe I need to check for holes in the crappy connection from the cat to the muffler.

[jeep ride]

If you can find a instrument cluster from a 97 / 01 xj you can replace your idiot light cluster simply by swapping them out I got mine on ebay .

[lawsoncl]

A cheap Bluetooth OBD adapter and a phone app can be quite helpful, especially if don't have the full dash guages. The poor mileage could be the O2 sensor, or perhaps the engine isn't fully warming up, or the sensor is bad and the computer just thinks it's not warmed up.

The valuable tool in your kit should be a multimeter so you can test before deciding to replace sensors. (yes, it's a pet peeve of mine)

On the fan clutch, the should spin relatively freely when the engine is cold. Onc e it's up to operating temp, it should have a lot of resistance and if you spin by hand it should stop within a full rotation or so. A bad fan clutch will usually only cause problems at slow speed and idle.

[XJI6191]

Originally Posted by lawsoncl

I would not blindly replace sensors unless you have good reason to suspect they're bad. The new aftermarket parts tend to be poor quality versus the oem ones.

Good advice, well put but it applies to every last part, except, of course, consumables & routine tune-up items like plugs, wires & filters.

[75SV1]

I bought some older NOS thermostats off of Ebay a year or so ago. The Carroll ones are all brass, and look of good quality. Robert Shaw is being made again. Over the counter, I'd try the Super Stants.

[myXJpeg]

OK, great. I will look up how to test O2 sensors along with doing the fan clutch test.

And try to do a deeper dive into thermostats.

Thanks

[boncrshr]

Originally Posted by myXJpeg

Also auto AX4 paired to 231 and the8.25 w 3.55 gears

The advice I give every new XJ owner is buy a new crankshaft position sensor, remove and replace current CPS and keep the known good one in your glove box + carry tool necessary to change it in the Jeep. That is the part most likely to leave you unexpectedly stranded.

[myXJpeg]

Originally Posted by boncrshr

The advice I give every new XJ owner is buy a new crankshaft position sensor, remove and replace current CPS and keep the known good one in your glove box + carry tool necessary to change it in the Jeep. That is the part most likely to leave you unexpectedly stranded.

Now thats a pro tip right there

[Anak]

I would recommend taking that tip one step farther: Slot both CPS sensors.

The CPS is not in a particularly convenient location. It is hard enough just to get a socket onto those bolts (you need about 36" of extensions, one of them being a wobble extension plus a universal), and to take the bolts all the way out and then need to start them again is a PITA. It becomes a royal PITA should you have the luck to drop one of the bolts down into the bellhousing (it happens). Oh, and don't forget, those bolts are not a standard, hardware store, sort of bolt. They have a special shoulder on them. At this point you probably have to find replacements in the junkyard.

You can improve the situation if you slot the bolt holes. Start by removing your original and seeing how your slots need to be parallel to the body of the sensor. Cut your slots (I used a cut-off wheel in a Dremel, plenty of other ways to skin that particular cat), loosely install your bolts and then check to ensure you can gracefully install your old sensor without removing the bolts. Once you get that done, take the old one out, slot the new one just like it and install the new one.

Now you are set up to be able to change out the CPS quickly and with minimal risk of losing a bolt.

[four_shot]

^^^This is damn good advice