Need advice for my high mileage (300k+) Cherokee

[Shoobie]

Hey everyone. I've been a lurker for some time, but I've been busy with other things, so I'm out of the loop. I'm hoping that you guys can help me decide what's best for my new-to-me 89 Jeep Cherokee. It has the 4.0l I6, auto transmission and 4wd.

As mentioned, the XJ has over 300k miles on it. It actually isn't running right now due to a leaky radiator (hopefully it's under warantee), but as soon as it is, I will take it for a long test drive to see how it runs. The P.O. said she didn't have any huge problems with it.

I'm thinking that it would be a good idea to start with the cleanest slate possible with this vehicle. I plan to, at very least, change the air filter, oil/filter, spark plugs, cap and rotor, and fuel filter. I also plan to begin Auto-RX treatments (although they'll probably take a while to complete). I think I'll pull the valve cover and see what it looks like under there (should I look in to adjusting the valves?).

I also think that getting fresh fluid (perhaps with some Auto-RX/LC?) in to the differentials, transmission, and transfer case would be a good idea. Then again, I'm not sure if this would cause more harm than it would help. I'm hoping that there are some dino fluids (read: inexpensive) that I could use and get good results.

I've tried wading through the search results (and I'll continue after I post this), but I can't find many threads with vehicles over 300k. That, and I'm lazy.

Any and all help is greatly appreciated. Also, any general advice is also encouraged, through PM if you don't want to steer the thread off topic. Thanks everyone!!!

 

[jeepman]

and congrats on the Jeep purchase. At 300k she is just broken in, and with regular maintenance should last quite a bit longer for you.

Based on your circumstances, I would change the transfer case, front and rear end, and transmission out with either genuine Mopar fluids or some equitable 3rd party semi-synthetic as called for by your owner's manual. The tranny dipstick should tell you if an ARX treatment is called for, but otherwise I would just go with straight fluid for all of the above mentioned parts, as the fluid does not break down as quickly in those parts.

For the engine, I would do an AutoRX rinse/clean cycle with Castrol GTX and then move to MaxLife 10w30 year round after. I have used many different oils in my 4.0, and even though the old Havoline was her favorite for awhile, I am afraid that the new formula may be too thin for that engine. My 4.0L seems to like really thick oils, hence the Castrol and MaxLife have really quieted her down at 163k miles, and get her running real smooth all the time. Or, if you can find some of the old Havoline on closeout at Big Lots, I would recommend that for the ARX phase, and then the MaxLife from there on out.

Also, the auto transmission, you may want to check the lines that run from the tranny to the cooler in the front near the radiator. Sometimes they will rust out causing a loss of tranny fluid and can burn up the tranny in a heartbeat.

Lastly, you can get a new radiator at AZ for about $130, but I would recommend getting the high capacity version for around $180. The OEM radiator for the XJ's seems to be a little undersized and can run hot in the peak of summer. Or you may want to consider using a 180 degreee thermostat year round, which is the route I went after replacing my radiator with the OEM version and finding out she was running a little hot in July.

Congrats again on purchasing one of the best built vehicles of all time IMO.

 

[Greaser]

What he said

 

[HardbodyLoyalist]

Given your location, I wouldn't hesitate to run 15W-40 HDEO year-round. My nephew has a '91 and the heavier oils suit it just fine.

I would also absolutely change every fluid in the vehicle, especially those that are usually neglected, like the differential (don't forget the front!) and brake fluids.

Does this have the AW4 tranny? If so, the good news is that they're bullet proof. The bad news is that reinstalling the pan so that it doesn't leak is... um... challenging. Don't forget to pick up a tube of Permatex high-temp gasket sealer before you drop the pan. And you might consider getting a few extra quarts of tranny fluid just in case you have a major leak.

I also second the recommendation of the high-capacity radiator. The cooling systems on these Jeeps are easily their weakest component.

 

[Shoobie]

Thanks for the replies!

jeepman: Do you have any suggestion for brands to look for/avoid? My research tells me that I need Dexron 3 for the transmission and transfer case, and 80w-90 for the differentials. Also, I'll check those transmission lines ASAP.

As for the radiator, the leaking one was still under warranty, so I got a free replacement. A cooling system overhaul is definitely on my list of upgrades, though.

Greaser: Thanks for the welcome!

HardbodyLoyalist: Why do you recommend HDEO? Does it offer better protection? Will the higher viscosity help an older engine? It does get kind of cold here in the winter (or I'm just a baby). If it makes it that long, this will be a bad weather vehicle, so would you still recommend a year-round HDEO?

Yes, it does have the AW4. Hopefully it keeps going.

Thanks guys! Any other tips are welcome!

 

[jeepman]

I run Pennzoil dino gear oil in everything except the tranny, and that gets genunine Mopar ATF+4 from the stealership. Those are all my 92 XJ has ever seeen, so can't really recommend or advise on avoidance of any other brands. I have had no problems with 2 changes on all components using these fluids over my 5 years of ownership. If I might offer some advice, I would say to double check fluid for your tranny, because it was my understanding that it should be either Mopar ATF+3 or ATF+4 for all XJ's, but I may be wrong on the older models.

Once again, welcome and congrats on purchasing one of the greatest automobiles in history. With 300k, you should still get quite a bit of fun and use out of your 89 XJ.

 

[Sparkman]

The AW4 gets DEXRON III. It's not a Chrysler tranny, so no need for the expensive bandaid fluid. There are countless anecdotal reports of poor performance with synthetic fluids in this tranny.

www.naxja.org/forum

 

[HardbodyLoyalist]

"Why do you recommend HDEO? Does it offer better protection? Will the higher viscosity help an older engine? It does get kind of cold here in the winter (or I'm just a baby). If it makes it that long, this will be a bad weather vehicle, so would you still recommend a year-round HDEO?"

The 4.0L Jeep engine sheds iron like it was going out of style. This is due, at least in part, to (1) the iron engine block and (2) fairly loose tolerances. I suspect that the loose tolerances explain the improved UOAs of 40-wt oils.

I tend to think of 15W-40 oils as 10W-40s with extremely stout additive packages.

Take Rotella T 15W-40 vs. FormulaShell 10W-40:

Visc@40C:

Rotella-T 15W-40: 120 cSt
FormulaShell 10W-40: 99.4 cSt

Unless you're talking about temps in the low 20s, then I can't imagine you'll notice much difference.

If you're really worried about low-temp performance, you can always use Rotella T Synthetic 5W-40 in the winter months (it's about twice the price of the 15W-40 HDEO).