I have an 87 xj with I believe is the open cooling system(no radiator cap and has overflow tank). I recently changed the water pump and now it wants to overheat. I figured I'd flush and do a cleanse on the system and while the water and cleaner was in it worked fine. I drove it around for a couple days with no problems. I flushed the system and added coolant but it want to overheat again. Tried the burping method with the the rear jacked up, even tried it with the passenger side jacked to elevate the overflow tank so air would travel up but nothing has worked. My thermostat works and cycles coolant around 180° or so. Any advice?

I thought burping the old systems required you to park nose uphill?

Or jack up the front and run it. To get the air out.

An 87 would be called a closed system. The open setup (a misnomer really) has a normal radiator cap and a non-pressurised overflow/recovery bottle. Make sure the cap on the surge tank is holding pressure. Loosening the water temp sensor at the rear drivers side of the head to help get the air out. If it's still overheating, check that the fan clutch is still good. Consider replacing the radiator if it's still the original. The cleaner might have knock enough crud loose to plug it up.

The Renix Era system is a closed system.

Did you check Cruiser's site for info? (www.cruiser54.com)

Perhaps a more detailed description of the overheating would be helpful. There's more than just air in the system that could cause problems - maybe it's a degraded water pump or flakey fan clutch.

You can ensure that the system is full easily by parking with the rear end higher than the front. Unscrew the temperature sending unit in the rear of the engine block on the driver's side. Fill the system. This makes that the highest point. As you fill the system it will eventually overfill at that opening. Clean the plug and apply a liquid or strip of Teflon to create a water-tight seal. Top off your coolant tank. That is a full system.
Not having the auxiliary fan turn on could cause overheating. The fan clutch not being in good order could case over heating. A loss of coolant in the system via hole in hose or not water-tight connection could cause overheating. Air in the system could cause overheating. The thermostat stuck closed would cause overheating. The temperature sending unit that I mentioned in the first paragraph being a bit off would show the gauge as overheating when it may not be overheating yet.