I have a 1990 XJ with 4.0L, auto and 4x4, got it about 8 years ago with 90,000 miles on it.. My question is it just turned over 110,000 miles and I was wondering when to replace parts or what is the life expectancy of parts, for example I found in the forums that the stock brass radiator is good for about 120,000 miles, just replaced mine it started to leak also did the rest of the cooling system at that time. I guess my main question is what would you think needs to be replaced, do I go by the age of a 30 year old vehicle or mileage. Because I will be starting to do some mild off roading and do not want to break down. I do all my repairs myself, just want to stay ahead of things needed. Thanks

 

That is always a tough call.
I say drive it. Perform proper maintenance. When something breaks fix it.
But mine is just DD and you being out there......
One thing I am big on within reason is what I like to refer to as the "While we are here" way of thinking.
Like how you did the whole cooling system.
Or when you have to tear the Jeep apart to fix something and now you have easy access to something.
Start thinking "well while we are here" should I replace that?
That can get expensive so I take that on a case by case basis.
But also my wanting to replace things, button everything back up, and hopefully never go back in there in my lifetime makes it hard not too. LOL.

 

I'd change all the fluids (noting condition for future investigation) hit all the zerks and inspect all the rubber bushings and hoses. Check your ignition system out (plugs, wires, rotor arm) and buy a spare Mopar Crank Position Sensor while it isn't urgent.
Then check your brakes and brake lines (hard and soft). If you keep your eyes open while doing all that you should notice if there's anything scary.
Oh, rust - you probably won't have to look too hard to find some! It's unlikely to stop you in your tracks but it's always best to treat it early.

Honestly, you could go on forever and change out every component but if you cover the basics and keep looking round your Jeep you should be OK.

Good luck!

 

My tie rod ends were shot at 120,000 miles. I noticed the ball joints had a little play in them too. I replaced the ball joints, wheel hub bearing assemblies and axle u-joints while it was apart to save from taking everything apart later on.

 

This is fantastic advise. If you are going to do something that will take you several hours to take apart, it does not make sense to reinstall an old part, especially one that is a wear item. If I am replacing the radiator, I am going to replace the hoses, thermostat, and water pump while I am at it (unless they were recently replaced). Just ask yourself, is it worth the money for the additional parts, or worth the aggravation of having to do the job again to replace the part.

 

If you buy cheap Chinese parts from your local parts store, you WILL be replacing everything again.

 

Do you have the owners manual? Those normally have maintenance schedules in them. You can go off that and inspect the things recommended to change and see if they NEED changed. And if you're reading the 110,000 mile schedule, you can always go back to lower mileage recommendations and see if there is something you know hasn't been changed or looked at in a while and check it out as well. If you don't have an owners manual, I bet there is info you can find somewhere on the internet for maintenance intervals for your specific vehicle.

Going by age only works for some things. Other things have to go off wear and tear. You wouldn't change your brakes if they only have 5,000 miles on them even if they're 15 years old...
Going by age works for something like tires. They may only have 3,000 miles on them, but if they sat in the garage for 5 years, they're probably cracked, the rubber got hard, and probably wouldn't hold up well when they started to get drove on again.

 

The prior posts pretty much cover it. I would never replace an original part or Mopar branded part with a piece of chinese junk unless the original part was not functional and the chinese junk was the only option. However, I always look for the "While I'm in there" stuff and if I can get a quality replacement part and the original is functional but on it's on it's last legs, I'll replace it.

The biggest thing for age is any of the rubber or seals and the such. If you're wheeling, you'll want to make sure your undercarriage stuff is all sturdy - steering stuff, uni-frame welds, drive line (apparently folks seem to bust u-joints like crazy on the trail) and bring some tools!

 

One comment on replacing parts. It is nice to have new spare parts on hand whether you are doing the replacing or a repair shop is doing the work. As an example, I keep a good supply of Timken bearings on hand in case an axle U-joint or a drive shaft develops a problem and a Timken can't be obtained quickly locally. Otherwise you may have to have some of China's finest installed on your vehicle. I'm down to 4 XJ's now, but I try to stay ahead on certain brand parts I want on my jeeps. The other side is getting what the local stores have available.

 

Funny you should mention the cooling system.
When I bought my Jeep about 7 years ago it was a kinda running not really driveable impulse purchase.
The AC Compressor had seized and took the belt with it. Could not test drive her.
So I bought a bypass pulley and belt. Fired her up. Noticed the radiator was cracked. So I had to replace that.
Went for hoses, thermostat, and because the lower tranny line had a notch in the rubber from rubbing on the steering box replaced that.
The whole time I was wondering if I should do the water pump. Thing was at that point I did not know where the Jeep was at.
Not having been able to drive her yet. Not wanting to sink to much in her at the beginning. I almost didn't do the hoses and whatnot either.
But figured what the hell but had to draw the line somewhere.
It worked out in the end but could have gone either way. The more the Jeep behaved herself the more I fixed.
I did end up doing a water pump last year though. LOL.

 

Age takes a toll on the electrical system by drying out and cracking insulation and forming corrosion on contacts. Plastic connectors start to crack when you have to take them apart. Taped harnesses start to come apart and expose wires to abrasion. Vacuum hoses also dry out and crack, making them leak. Purge out the brake fluid with fresh because it's probably never been done. Brake fluid absorbs water and over time can rust internal parts of calipers and cylinders, even steel tubing. Brakes are the most important system in automobiles because no matter how fast it goes, it's GOT to be able to stop! If it's been parked for an extended period of time, rodents can do quite a bit of damage by chewing on wires and hoses. Anything that can absorb salt is part of their diet. They build nests out of insulation and seat stuffing. My 37 Dodge barn-find had moth worms in the carpets. Gasoline left in the tank can turn to varnish and water rots it out. Your 90 may still have a steel tank.

Mileage wears out bearings and gears. Any parts other than the engine and transmission internals are easily replaced. Springs sag and shock absorbers wear out. Then there's the cooling system. If it didn't have a sufficient amount of antifreeze in it, the water can cause rust to clog everything up.

That's about everything I can think of at present. After I got my 37 Dodge on the road, I had a notebook with me every time I drove it and wrote down things I had to fix when I had the time. That way when I HAD the time, I didn't have to remember what needed to be fixed the most.

 

One thing any driver should do is make it a habit to open the hood at least once a week and eyeball everything, checking fluids, and looking for leaks. It can save you from being broken down on a lonely dark road at night.

 

I knew if I posted this I would get a lot of work haha, I mean useful information. I am one of those people that say while I am here I should replace parts so I don't have to late. Like the cooling system, I did the radiator, water pump, all hoses and belt and thermostat, flushed and new coolant. I just retired and have a lot of time to send on the jeep. I have been working on cars before I was driving, so I have no problem with repairs also went to school for auto tech (many years ago) and worked in the field for about ten years. I could write a book on what I have done on this jeep in the last 8 years. Just wanted to give it a good checkup, trying not to forget anything before I start using it more and going more places. Thanks everyone for taking the time to reply.

 

Not a problem. That's why we're here, to share information and make you wiser. I lost my wife, then retired, THEN bought my first jeep because it was something I'd always wanted to own but couldn't convince myself I needed. I got a lot of information on what to buy from this forum before I bought one. What to look for as far as defects and possible repair items and what to expect when problems came up. I've been here ever since! Good bunch of guys and not many trolls. They don't last long. For your 90, Cruiser 54 is the guru.

 

All of the above is good advice. I would jack up the front wheels and grab the top of the wheel and try to rock it. If there's play, could be wheel bearing/hub. Not hard to replace and if you've never done one since you've had it, chance are they are due. If no play, you're good though (I wouldn't replace them unless you found play). Lots of videos on how to do it as well.