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Because my jeep has no heat and I changed the thermostat and the rad not long ago, I have narrowed the problem down to a busted damper or clogged heater core (i think). Both h-hoses are warm at operating temp and no overheating. once it hits 195 it stays.(could this mean a stuck thermo?)
Also, when the rad was changed the system was flushed. If the h-core was clogged would this have taken care of it?


When I replace the hoses after flushing do I need to get rid of the air I have introduced to the system, or can I just plug them back in and fill at the radiator? Any other tips would help and I'll let you know how it goes.

97 4.0 5-sp no ac
 

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If both heater hoses are warm when running at temp then you have flow, it shouldn't be plugged.
When you change from defrost to floor to vent do you hear the little door change position?
Is your fan working?
Are all the ducts connected right?

If you disconnect the core you don't need to evacuate the air, the water pump will take care of it.

If you put in a 195 degree thermostat then your temp will stay around 195 and shouldn't drop below.
 

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the blower works on all fan speeds except defrost. there is little air coming from the top of the dash where it should be defrost

I do hear a door during the defrost to floor change.
not sure about the duct connection. How can I inspect it? behing the dash?
I have also tried all settings.

the only time I feel the least bit of heat is when I run the fan on the cool setting and then immediatly switch to heat and it doesn't last long
 

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you can open the dash from above.. the panel with the holes made for the window defrost pulls straight up (screw driver should work) and then there are few screws to remove the front area around the stereo. 2 or 3 screws on top visible after removing the preveus panel and then 1 behind the ashtray.

Thats as far as i know for removing the dash parts.
 

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Since you heat doesn't last long, I'd bet you have low-coolant flow through the core, and after a couple of minutes, what heat there IS there is sucked away by the air flow.

As was mentioned, BOTH hoses should be hot when the Keep's running. If the heater is off, the hoses should essentially be the same temp. If you have the heater on HOT and fan HIGH, the return hose will be cooler (since you are removing some of the heat into the cab).

Pull the heater hoses at the engine (plug the engine to save your coolant, collect what runs out of the heater hoses and put it in your recovery tank), then using full pressure from a water hose, blow both ways through the heater hoses (leaving the other hose unconnected when flushing). I'd be willing to be you have an obstruction in there somewhere, and alternating flow directions might unclog it.

Bob

the blower works on all fan speeds except defrost. there is little air coming from the top of the dash where it should be defrost

I do hear a door during the defrost to floor change.
not sure about the duct connection. How can I inspect it? behing the dash?
I have also tried all settings.

the only time I feel the least bit of heat is when I run the fan on the cool setting and then immediatly switch to heat and it doesn't last long
 

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Having the same problem with my 98 TJ 4-cyl. Found this useful information below, while searching the web. :wavey:

Heater Core Flushing Made E-Z

I had a problem with my XJ's heater not providing very much heat for a long time,
and it continued to get worse as time went on, until the heater barely got warm at all.
I had flushed my cooling system (annually) but this did nothing for the heat problem. The design of the XJ's closed cooling system, doesn't allow the routine engine flushing process to really get the crud out of the heater core, so it tends to build up over the years and eventually reduces the flow to near nothing.

Since I had just flushed the entire system, and I didn't want to drain and refill the system again, So I figured out a way to flush just the heater, and leave the rest of the cooling system intact. I went to the hardware store and bought 2 feet of 5/8'' and 2 feet of 3/4' heater hose, and a 5/8 & 3/4" female garden hose coupling replacement kits (look for the type that use hose clamps), and 2 rubber stoppers (or corks) to fit snugly inside the 5/8 & 3/4' hose.

The only preparation that needs to be done, is to install the female hose couplings on their respective pieces of heater hose, and park your Jeep where the flushing won't make a mess (preferably not on the grass, antifreeze is a great de-foliant and will kill your lawn). The 2 foot lengths of hose, gives you enough to route the flushing output down out of the bottom of the engine compartment, so it won't get the gunk all over everything.


Now remove the vehicle's heater hoses from the core, one at a time, and quickly cork the end of hoses before any (much) coolant leaks out. Then attach the two short pieces of hose to the heater core input/output, using the clamps from the heater hoses to secure them in place. Now starting with the lower 5/8" hose, hook up the garden hose and give it a full blast shot for about 30 seconds. This should unseat gobs of crud. Next, go to the upper 3/4" hose for a shot, then back & forth a few times 'till the water runs clear, ending with the lower hose.

Now you can turn both hoses up, and fill the heater core with water, then starting with the lower hose, pull the flushing hoses off, and hook up the heater hoses quickly to avoid any (much) loss of coolant. Just top off the reservoir and you're done. (The amount of water in the heater core will not significantly change the ratio of coolant. If you're really concerned about that (or live in Alaska), just use antifreeze to fill the core and the top off the coolant bottle.)

The whole process took me less that 20 minutes, (not counting the trip to the hardware store...), and now I have H-E-A-T! So much heat in fact, I have to turn the temp control down to 1/2, even when it's below freezing outside.

Have fun, and keep warm.
 

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We blow em out with compressed air at the garage......works better than water and its faster......beats pullin the dash off ta boot....g
 

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We blow em out with compressed air at the garage......works better than water and its faster......beats pullin the dash off ta boot....g

I agree with the Dash removal craziness.

After reading this section I've decided to stop mid way in the process and try a flush and a thermo change.

Should have read this first ... grrrrrr :banghead:


Edit ** Whoa ... my bad, sorry for calling up a 12 month old post. I read the NOV as an 08 Nov.
 

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Whatever you do DO NOT use your houses water pressure to flush it, you can stick a garden hose in there with the hoses disconnected but don't seal them tight, that core is made to take a very limited PSI, your cap is set for 16PSI, your houses water pressure can be in excess of 60PSI, you put that kind of pressure on that heater core and it's blocked you will blow the core apart.
Just use the hose, alternate between the two bungs till you get a clean steady flow in both directions.
When you remove the heater hoses from the firewall don't just remove the clamps and pull them, you stand a good chance of breaking the core bungs. Slice the hoses lengthwise and peel them off gently. Then put the new hoses on and use those hoses to flush with, you can get them out the side of the engine bay so you are not dumping gallons of water into the bay and around the electronics. If you have a long enough garden hose you can also use hot water from your hot water heater in the house, most have a drain petcock on the bottom somewhere. I use it every year to drain sediment from my hot water heater :D
 
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