Heater Problem 1999 Cherokee Sport

I know this must have been addressed previously but threads that I have read were confusing to me so I wanted to start fresh.
Problem: I own a 1999 Cherokee 4 wheel drive ( I have seen2 wheel drive models)
My engine temperature slowly creeps up to 200 deg. and stays there with little or no change in temp. The coolant is clean and full.

I have the heater set to on and The air blowing out at the feet feel Luke-warm and no where near hot.
I recently replaced the Thermostat with a superstant 195 deg Thermostat and that seems to have had little effect.

My guess is that my next check should be the heater core
What should my next course of action be. You can be specific as I am a technical type.

Pull both inlet and outlet heatercore hoses at the front of the engine, point one down and hold a garden hose up to the other to fill/test the heatercores flow. Start slow in case you have a blockage. Report back with test results.

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I would love to try that but I live in the Northeast and the temps right now are below 10 degrees. All outside hoses are stored for the winter and all outside spickets are purged to prevent freezing and rupture. :doh:

Your heater core is probably clogged. The best way to flush it is with a garden hose at moderate pressure. High pressure water or compressed air can burst the heater core.

Yeah I would recommend flushing your heater core also, sounds like that might be your problem, unfortunately its do damn cold for that. You can try another option if you like. I read this somewhere but I dont remember where now, sorry! You can use compressed air to flush it. Get a compressor of course and you need to make your self up something where you can mate the heater hoses and the air hose. Like some barbed connectors and hose clamps or something. But when you use the air you need to find a way to regulate it, like crimp the hose off, or they sell hose crimpers for like brake lines and whatnot. You want to use very little pressure just enough to get the gunk out. The heater core is fragile and trust me you dont wanna have to replace it, if you dont need too. Anyway after the first blast of air, pour in some CLR (you can buy this at home depot or lowes) down the hose into the core and let it sit. Then repeat the process with the air. Finally, pour some water in and use air again to flush out the CLR. Top off the coolant, and see if that works.

Disclaimer, I've never tried this my self! But I dont see why it wouldnt work.

I just got done doing this last month to mine. After doing a bunch of searching and reading on here about heater issues I was dreading the task of flushing, just in case it didn't work. So I flushed the heater core as described above (removing the FRONT of the hoses from the T-stat housing) so I could guide it where I wanted it to drain. Flushed everything until it ran clear (out of the heater core). It didn't work. So I completely replaced the hoses, T-stat, drained and flushed everything again. After draining the fluid into a 5 gallon bucket, my coolant looked like mud from the rust and debris. Filled/buttoned everything back up, STILL didn't work. I started to carry around a huge marshmallow type jacket to keep me warm because I was not going to tackle the heater core, or pay anyone to do it either. After a couple of weeks of driving around like that I thought I would give it one last shot. Went to Lowes, picked up one of the "firehose" type nozzles for the garden hose, went home and disconnected the hoses from the housing, shoved the end of the nozzle into the hose and slowly twisted the nozzle so that it didnt give the "jet" effect. As I did this I looked under the Jeep as it was flushing into the bucket and watched globs of stuff pour out. Hooked the houses back up started the Jeep up and let the system burp the air out and added back what was lost. I had to do thise about 5-6 times all together while in between each time, starting the Jeep and letting it burp the air out and warm up (with the cap off of course).....And FINALLY hot air!!!! It now gets so hot that I have to turn the temp knob down some, and the best thing about it all was that it was FREE!!! Other than the nozzle (which needed to be replaced anyway). Flushing the heater core worked for me, just don't give up after the first time you try it and you don't get hot air is all I'm sayin'.

1. Go purchase a radiator CLEANER made by Prestone, Zerex, or others. You want the stuff you put in and driver for 3-6 hours (it can be over multiple days).

2. Follow the directions.

3. After neutralizing the radiator CLEANER, but before adding new coolant, back flush the heater core as described by the others.

Note that a common thread here is that you will need a garden hose.

FTW: this is called cooling system maintenance, and should be completed on a regular basis, like every two years.