I'm trying to help my friend to buy 1990 xj.
http://losangeles.craigslist.org/sgv/cto/3760611694.html
i don't really know about xj cherokee and old jeep.
so could you guys let me know what should i check and how?
I would stay away from anything 91 and older. Simply because the vacuum lines are a nightmare on the early models, and in late 91 they changed to an open cooling system which is simpler and works much better than the closed system in the early 91 and older models.
Some models that had the heavy duty tow package had a d44 in back, but usually it is a d35 or a chrysler 8" rear diff.
The one common problem I had on both my XJ's (90 and 91) was the rear main seal blew out and had to be replaced. Otherwise oil leaking out of that seal would drip on the exhaust creating a cloud of burning oil. So look for evidence of burned oil on top of the exhaust where it crosses under the engine. One of my XJ's also leaked oil from the valve cover, but that is an easy fix.
If it is a closed radiator system, make sure the coolant tank on the firewall is not cracked. The engine will overheat if the closed system doesn't stay closed. Consider changing it to an open system from a 92' model year or later.
Check the usual problems you would expect from any used 4x4.
U-Joints in the drive lines and front axles.
Does transfer case work
brakes?
does engine burn oil.
oil in coolant.
steering in good condition? I had a steering box on one that broke away from the subframe, and another that decided to loosen it's bolts.
Do the doors open and close well. Since it is a unibody rig, doors having trouble is an indication that the body is tweaked.
Will it pass emissions and/or inspection based on where the rig will be licensed?
All of this is of course dependent on the price and how much mechanical knowledge your friend has, how much he wants to spend on parts, and how much time he wants to spend wrenching. A worn out rig can be a good deal if you know what to expect and how to fix it. It will be a bad deal if you depend on it for a daily driver and don't know how to fix it.
