You just picked up an XJ. Maybe it drove well, maybe the seller gave you a stack of service records. Either way, the right move when you first get an older vehicle is to start from a known baseline. Don't assume anything was done. Verify it yourself, or take it to a shop you trust and have it verified there.
Here are the jobs to tackle first, in order of priority. Complete the safety items before anything else, then work down the list.
Inspect the brake pads and rotors before driving the vehicle more than a few miles. On an older XJ you don't know, pull each wheel if you can, or at minimum look through the spokes with a flashlight. Thin pads, scored rotors, or seized calipers are all immediate safety concerns. Brake fluid should be clear to light amber, dark, milky fluid means it's absorbed moisture and should be flushed.
The rear drum brakes on XJs are often neglected because they're not visible without pulling the drums. Pull them. Check the shoes, wheel cylinders, and hardware springs. Rusty, frozen hardware is common on vehicles that were not regularly serviced.
Check tread depth and inspect sidewalls for cracking. Dry rot can be invisible until a tire fails at highway speed. Look at the date code on the sidewall, four digits, last two are the year. Tires over 6–7 years old should be evaluated carefully regardless of tread depth. Inflate to spec.
XJs overheat. Before you drive it seriously, look at the coolant level (cold), squeeze the hoses, and check for any white residue around the radiator cap or hose fittings. If the coolant is rust-colored or hasn't been changed in an unknown period, flush and refill immediately. This is cheap insurance against the most common XJ failure mode.
Change it regardless of what the seller said. You don't know when it was last done. Fresh oil is cheap. Fresh oil in an engine you don't know the history of is essential. Check the color when you drain it and look for metal particles or a burnt smell.
On AW4 automatics: check the dipstick. If the fluid is dark and smells burnt, have it serviced before driving it hard. Pan drop and filter replacement is the thorough option. Topping off dark fluid doesn't solve the underlying issue but at least shows you what you're working with.
Pull the drain/fill plugs and check the color and smell of the fluid. Fresh gear oil is amber and relatively clear. Old gear oil is dark, thick, and metallic-smelling. Changing all three (front diff, rear diff, transfer case) is around $40–80 in fluid and a straightforward DIY job. Do it.
If you don't know the history, flush and refill with the correct coolant mix. The 4.0L engine uses a standard 50/50 mix. Old coolant loses its corrosion inhibitors and becomes acidic, accelerating head gasket wear and erosion of the radiator.
Often overlooked. Check the reservoir, it should be full and clear to amber. Dark, foamy power steering fluid suggests worn seals or contamination. Flush and refill if it looks bad.
The 4.0L takes six plugs. Pull them and look at the condition. A proper plug inspection tells you a lot about engine health, oil fouling, coolant fouling, lean or rich running conditions. Replace them with Champion RC12YC or the equivalent. Gap to spec (0.035" for most 4.0L applications). This alone can improve MPG and starting.
Pull the airbox and inspect the filter. If it's gray/brown and clogged, replace it. Clean air in = better combustion.
Located on the frame rail. Easy to replace, often ignored. A clogged fuel filter restricts flow and puts stress on the fuel pump. Replace it if you don't know when it was last done.
Cheap to replace (under $20), significant impact. A stuck-open thermostat keeps the engine running cold, hurting MPG and accelerating wear. A stuck-closed thermostat causes overheating. If you're doing a cooling system refresh, do the thermostat at the same time.
Inspect the serpentine belt for cracking, fraying, or glazing. Inspect all coolant hoses for firmness and condition, squeeze them cold; they should be firm, not soft or crunchy. Hoses have a finite service life and rubber deteriorates faster in hot climates. Replace anything that looks questionable.
Once the immediate safety and maintenance items are done, get underneath and do a thorough inspection. Shake the front axle components by hand looking for play in the track bar, tie rod ends, and ball joints. Look for oil leaks at all drain plugs, axle seals, and along the transmission and transfer case. Check the exhaust for rust-through or loose hangers.
This inspection will tell you what else is coming. Better to know now than have something surprise you on the highway.
Most of the jobs above are within reach of any owner with basic tools and a free afternoon. If you'd rather have a shop handle the initial assessment, take it to a shop that knows XJs. Describe what you've bought and ask for a thorough initial inspection. A good shop will flag what's actually urgent versus what can wait.
The XJ is a maintainable vehicle. Once you know its baseline, it's easy to keep ahead of problems. Start here, work the list, and you'll be in a much better position within a weekend.
