Cherokee Cooling Issues

1988 Jeep Cherokee I6 2wd

The Coolant Bottle + Cap are brand new, as are some of the hoses. All hoses in good condition, clamps tightened etc. It seems no matter how much water/coolant I put in, it blows the cap clear off the bottle. First, the fluid level went clear to the top of the bottle, and the cap landed 10 feet away. Second, my guess is that there was not enough fluid and the cap again exploded. Cap Tight 100%, cap tight 80% makes no difference.

I plan in the future to switch to the open radiator system provided the jeep runs good and lasts, (just got it). I've read alot on the forums about purging the air "burping" the system. How important is this, and what is the best way to do it? There is air in all hoses when engine is cold. They fill when engine has been running about 2 minutes.

Is the cap blowing because of the air in the system, or because the cap is too lose/tight? Also on top of the new coolant bottle there is a metal threaded fitting, that appears to go nowhere, but with those threads I have to wonder if it is important/ should have something hooked up to it?

Any help is greatly apprieciated. All cooling/heating cycles are done at idle, with inside fan on high.

Thanks,
Bryan

Additionally, I've read there are to be 2 fans. However I only see 1 behind the radiator (mechanical) runs anytime the engine is running. Should there be, and where should the second (electric) fan be?

EDIT: Where is the Temp Probe Located? And the mechanical fan, does not rotate freely by hand, takes a little nudge to move it, is this an issue?

its a thermostatic fan and yes it should have a little resistance. to purge the system fill it up with coolant, leave the cap off the degas bottle start the engine and turn the heat on high. let it run and make sure you feel the heat from the heater. if not then rev the engine up and then let it drop to idle multiple times you might see coolant gushing out but thats ok, just dont let the car overheat. if some of the air is still in the system, fill it back up with coolant and drive it around the block. rev that sucker up through the gears and then start doping gears slowing down on compression. bring a bottle of coolant with you just in case you need to add some. you can also try taking the heater core hose loose from the firewall when filling with coolant until coolant pours out then reconnect , that normally takes most of it out. other then that go buy a mighty-vac (i think thats the name)and air compressor to run it. just rember, no heater, no coolant flow. dangerous
you could have other problems like a thurmastat problem, internal engine,a bad(new) cap not releasing pressure,etc..
what color is your coolant, what does it smell like? did it overheat /problems before you drained the coolant? did you drain the coolant or did it just blow it all out or suck it all in? please give a little more info on the history

Thank-you for your prompt reply.

This vehicle sat for some time, and I just received it free from a friend, who warned me that it may need a new water pump. I'm not sure how to tell, as the upper radiator hose has flow. Not a real hard hose, but it does flow.

I drained the nasty coolant that was in there and put 50/50 back in. Yellow. Sweet smelling.

As far as the heater. When I first got the vehicle it did not blow air at all. Then after Tropical Storm Fay, it decided to start working. The air is not very warm when the engine is running. Perhaps I should start looking here along with the water pump/ thermostat.

Also, could you tell me where to find the Temp probe, I hear that is a good spot to bleed air out. What should I look for on the heater issue?

Thanks,
Bryan

EDIT: My jeep does not have a temp guage. Only a dummy light. The light has never come on during any tests, and I shut her down whenever there is a coolant issue during testing.

tords the back , right corner, close to valve cover. if i remember correctly

Far as I can tell, all air is out of the system. Did the cap open/run/shutdown add/run sequence. Opened the temp probe and got more air out, the coolant level is where it should be. We'll see if she stays cool with that, or if I still need that water pump.

New question: How do I go about adding a water temp guage off existing wiring, i.e. dummy light only?

And unrelated question. What is the best way to drain the fuel tank, without dropping it?

Thanks!
Bryan

you will need to get an after-market temp gauge. they are easy to install. it just pops in and a wire or pressure line runs from the gauge to the sensor. cherokees have a couple of holes in the firewall that are covered with rubber plugs. so getting the line into the cab is easy. just go out and buy one and slap it in. otherwise you can go to the junk yard and buy a cluster temp,oil,voltage gauges built in. take the sensors off the doner car because they are different. there is a lot of info on that conversion online because of the 4-wheelers.
you will ether have to drop the tank, take a suction hose down the filler neck(sometimes not posable),or if the tank is almost empty, take the pressure hose off of the fuel rail and cycle the key. turn the key to the "key on engine off" position for 30 seconds then back to the "off position", do this for a few minutes and let the pump take a rest then repeat. the best way is to drop the tank. you can get everything out of the tank that way. open the fuel door and take the screws out. if you can disconnect the fuel lines now then do so. look for a pvc type hose (evap) and disconnect that if you can git to it. along with any visible electrical connectors. if none then you will have to wait for them. take a jack and put it under the tank such that it can hold the weight. take the 2 bolts off that hold the straps and slowly lower the tank. looking for any of the above things that you could not get to before. to install go in reverse order.