My brother has one of these and it keeps over heating, we replace the head gasket had the head shaved and put a new thermostat and water pump on it and it ran fine for about 3 days and it did it again spewing coolant every where. Whats wrong with it? Im lost!   

Wow still no one has any ideas for this one?  

Check the clutch fan. With the motor off and keys in your pocket. grab ahold of the fan firmly, and try to turn it one way then the other. You should find that it has resistance. If you feel no resistance then it is bad.

Another thing to check: with the engine cool, trace all of the coolant lines looking for a purge valve, if a purge valve is present then you must let the air out of the coolant system with this before the engine will completely fill with water.

One more thing to check: pull a heater hose off while the engine is cool, have a bucket ready. Start the engine and see if any water is circulating. If no water is circulating, then look to the pump, clogged heater core, or radiator clogged. Hope I helped. Ride safe and keep it wheelin  

Another thing to check. Does your '88 have a pressurized coolant reservoir? If it does, you may need a new reservoir. I have a '90 Cherokee with the pressurized coolant reservoir, and since it's plastic, the threads started stripping out and I had some of the same problems you seem to be having. You can get a new tank from Jeep, but it's expensive. I got a new one on eBay that is tougher than stock for like $40. Have not had any problems since I replaced it. They only used the pressurized tank on about 3 year models of Cherokees before they realized how crappy it is, and I can't remember now if any of the '88's got it or not. I also got a oil filter cooler, (another eBay find) which is just a wrap-around heat sink that clamps onto the oil filter with a pipe clamp, but it seems to help bring the engine temp down a few degrees. And yeah, make sure you get all the air out of the coolant system after you do anything to it. The best way I've found is park so that the front of the Cherokee is pointing downhill so that the valve on the back of the engine is uphill and all the air can get out. Good luck!