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I seen this post about a month ago maybe lil longer and can't seem to find it, well I am having the same problem.

start the jeep gets up to temp, turn the heater on high, and it comes out hott for about 2 seconds or so then cools down, checked coolant level-fine, replaced T-Stat, along with the right mixture of coolant/water.

now what ya suggest., I ussually just figure it out myself but it is too damn cold out to tinker, it's getting down to the mid teens here in PA.

a clogged heater core can do that.see if one heater hose gets real hot and the other one is way cooler

I agree sounds like your heater core is blocked. Try blowing it out with compressed air, have to unhook both heater hoses and putting air to one end of the heater core. Had this happen to me last winter. Big Pain in this weather.

yea I know what you mean, thats exactly what the problem is the heater core is plugged (inlet hose hotter then the return hose) so I guess I will have to reverse flush it, or maybe the air compressor will do the job.

Thanks guys, I didn't want to go tinkering around out in this cold ass weather.

i dont know if i would put too much air pressure in a heater core.usually the old garden hose hooked up to flow backwards does a good job.sux to play with the hose in the cold though

I probally should have said that usally try around 40lbs. Never blew one at that pressure.

GREAT NEWS!

I flush and revers flushed the Heater core, and flush the radiator and engine of all the old coolant, then used some Prestone Super Radiator Flush, and chemical flushed it at a high idle (1500 - 2000 rpms) for 20 minutes. and then had to refil the radiator cuz it was low and my temp sky-rocketed, then fast idled again for about another 15 minutes, then flushed and reverse flushed the heater core a couple more times, and flushed the radiator and engine again to make sure all the chemical flush was out. Refilled with new coolant and boom heat again.

Thanks guys, I really didn't want to be standing out in this weather fuckin around with shit to figure out what was causing my problem, the heater core was deffinately clogged and the flush/reverse flush and then checmical flush of the whole cooling system did the trick, oo and if you wondering why I wrote everything I did to get my heat back, it is for further use for other people.

one more thing, washing machine hoses (to hook up the hot and cold water lines to a washer machine in your house) works great for flushing the heater core. I cut about 8" off one end, then used the threaded end to screw onto the garden hose, and the other end of that hose slides into the heater core hose and used the clamps already on the hose to clamp it down, then the other half of the washer machine hose slide it into the return hose of the heater core and turn the water on and let it run, then hook it up the opposite way to reverse flush.

hope this helps, the washing machine hoses made this job much easier.
Thanks for all your help XJ and CAM.

Great idea on the washing machine hoses I'll have to try that!