"BURPING" a cooling system

What's the most effective way to burp the air out of a cooling system? I got the radiator and fan (thank you 85CJ7 and Astape) hooked up and dumped a good 2 gallons of coolant into the radiator. I kept it running for 5 minutes and the temp gauge didn't register (mechanical gauge hooked to the intake manifold).

I took it for a drive and the temp began to rise steadily to about 200 but then it suddenly dropped back down to 160. Afterwards, the upper hose was hot but the fluid level did not drop at all.

I cracked open the heater core line and where the temp probe is screwed into the intake while the engine was running. Only antifreeze come out.

Is there an easier way or do I just have to keep doing it? Will driving it on the road without the radiator cap eventually get the air out?

The more I mess with it, I'm beginning to think the shaft to the water pump is snapped or the flange is spinning on the shaft.

I drove it to Carousel and back (probably shouldn't have) and the temp never got higher than 160.

I think I'm going to just replace the water pump.

I was able to remove the cap of my flush port (hose going to the thermostat) with the Jeep running and didn't have any sizable amount of pressure coming through. Since that hose is hooked directly up to the pump antifreeze should have shot out. I think the temperature I was getting was just radiant heat traveling through the water in the system (not from flow). I also cracked open the temperature probe port a few times to get any air out. Nothing but antifreeze came out.

I'm going to remove the thermostat and run the motor first. I'll also test the thermostat.

Thanks for the advice.

Thermostat was fine. I bought another water pump ($22+) and installed it last night. Then, when I was putting the thermostat housing back on I heard "CRACK". The darn housing broke because "I believe" the thermostat slipped out of the hole it sits in while I tightened it down. I grabbed a spare housing, did the swap, and when I put the upper radiator hose on I realized that not all 258 thermostat housings are the same! My spare was for a V-belt set up. The housings used for a serpentine belt system are angled back slightly so the belt doesn't slice through the radiator hose. I grabbed ANOTHER spare (from a 4.0L head) and it seems to be the right one. BUT.....THAT one has a threaded hole for a temperature probe. I didn't have a ½" pipe fitting to close that hole up so I couldn't get it installed last night.

Quote from 4x4fun

i dont know whats worse his luck or the fact that he had three right on hand

I save stuff.

I looked at the old pump and there is a shiny ring on the shaft where the pulley would have rested. My thinking is that the shiny ring would have formed if the hub slipped on the shaft. I also had to file the hole on the pulley slightly to get it on the new pump. There appeared to be a slight burr.

I put the thermostat back in since it worked fine while in the boiling water on the stove. Once I got it buttoned up again I didn't get any better results initially. I decided to take it to work anyway, figuring that either the new fan is OVERLY efficient or I still have an air pocket. I put a piece of cardboard in front of the radiator to MAKE it get hot. Most of the way to work, the temperature stayed at 160 but it DIDN'T spike to 200 and then drop like it did before. I began thinking what if the problem is in my mechanical gauge? But then, why would it have happened the same time I had the fan issue? That seemed too coincidental but is possible. I also began thinking that maybe the spring in the thermostat was faulty and it was opening too soon. Is that possible? I always thought they either failed open or closed.

About ½ way in the temp went up to 180 and stayed which I was happy to see. By the time I got into work the temp was at 200 and holding. So it seems like it's working itself out. I'll remove the cardboard from the radiator to see if it will act normal without it.

At least I'm getting a result I like. I guess the gauge could still be wrong and reading 40º LOW!