heat prob for expert not heat have checked a lot

91 jeep cherokee
so far i have checked flapper it's working. checked flow though core it's ok. replaced thermostat. recovery tank gets hot. no control valve in line to core. still no heat. blowes cold even after a drive. any advice on what to try next ?????

91sport, Welcome to AF. You posted in the "how-to" section, which is for solutions. I've moved your post to the general Cherokee section, it will get more exposure and a quicker resolution for you. On to your issue....

Sounds as if you've looked under the dash. I'm sure you have made sure you have flow through the hoses leading to and from the heater core. Do they get warm to the touch when your Jeep is up to operating temperature?

Have you checked the vacuum hoses under the dash that control the flapper door? These can age and crack over time, losing effectiveness.

have flow though core removed hoses and ran water though them also tested for leak by setting hoses up with water in them level stayed the same for 30 min
top hose gets hot but cold on bottom (exit) changed thermostat stayed the same resivior tank gets hot. it has no control vale in hose line to core and "flap" is cable controled and is working can hear it going thump thump when moved from hot to cold
also have "burped" the system ( capless radiator ) several times with no help
temp gage also changes as running goes from slightly below to slightly above 210 mark
this is why i said it was for the pro have tried all i know to do and have asked several people i know and i'm out of ideas on what to try

Have you pulled the water pump and checked the impeller. Are both the lower and upper radiator hoses hot?

If you're getting good flow through the system (water pump ok) and have no other cooling issues, it has to be the heater core. You can have flow through the core, but it could be sufficiently restricted to not give you enough heat when the weather gets really cold....this is what I'm getting from the heater hoses getting hot on one side, but staying cold on the other.

I would disconnect both hoses at the heater core and have someone start the vehicle briefly to check flow..The only reason I say to disconnect both hoses is I'm not sure which is feed and which is return...

have flow though core removed hoses and ran water though them also tested for leak by setting hoses up with water in them level stayed the same for 30 min
top hose gets hot but cold on bottom (exit)
if your talking about heater hoses then your not getting flow through the core
its either clogged or air bound

Some of these engines used heater hose with formed elbows check for a pinched hose.
If both bottom and top radiator hose is hot the pump is working.
Disconnect return hose with a five gallon bucket to collect anti freeze.
If the water is flowing the core is bad or a blend door is bad. Some of the older engines have a vacuum controlled valve in the heater hose line to shut off flow and control heat. These are a major problem area.

If the intake side of the heater core is hot and the lower is cold than than you have a partially blocked core. Try to force water through it in reverse. Have seen this happen before.

thanks for the input have tried all of this even did flow test though core no blockage even tested for leaks set up hoses and added water let set 30 min with no level drop was wandering if reverse flow could cause this with the capless system and "sucking air from top of resivior instead of water from bottom know on new systems they are set up not to pump so not to drain system in case of break in core not sure on flow asnot in manual and was "rigged" before i got it ( cut spliced etc.)

P.S. no other coolant problems even repaced thermostat thinking maybe it was stuck open went with hotter level and gave shows adjustment went from below 210 to jusat below to just above as therm works

also ran water though core both directions to check for deposits getting caught this is why i'm as puzzzeled as i am shortly before i got it pump was changed system fluid is very clean and green just thoght of anouther question could this be the wrong pump in book it talks about reverse flow pumps depending on serp or v belt could they have installed wrong pump causing this

in book it talks about reverse flow pumps depending on serp or v belt could they have installed wrong pump causing this

i think it would be hard to switch belts.is yours a 1 belt serpintine that drives
everything??do you still have 1 hot 1 cold heater hose??

If both the top and bottom radiator hose get hot with circulation through the radiator the water pump is working properly. A belt can be installed wrong running the pump impeller backwards.
Even a partially plugged heater core will allow both the top and bottom hose to get hot.
Gasket material stuck in a heater hose opening can block flow through the hose. Trace the heater hose from the two hose connections and make sure it doesn't have a valve in the line.

you must have a broken/cracked blend door!!!

does it get cold or cool???? is the ac clutch staying on....

yes still have one hot one cold hose as far as blocked core have ran water thrugh both directions with no dirt coming out

as far as broken/cracked door can hear it flopping back and forth with lever aand would think that i would at least have some heat coming out if it was that not to mention the one cold hose

if not familiar with this system two hoses come off pump/moter then go to two t"s one t goes to in on core and in on resivuor then the other t goes to out on core and out on resivour (reason for asking about wrong flow direct) wondering if flow bacwards would causethis due to sucking air from resivour causing pump to see air and stopping flow seeing it as crack in core

as for the revese pump if it is on a moter with v belts it turns one direction if using serpintine belt turns oposite have to get right one for what you have and wondered if they installed the wrong one before i got it ( i would have replaced it myself ) would reverse flow cause this and not cause an overheating problem with moter because moter runs fine and cool

also no valve in hoses have went to jyard and seen one on one there but all i have is the vac line hanging close to where it prob should be as i said been rigged before i got it looks like valve was removed or cut off the t it was on on the one in the yard all i see this doing is giving it full flow all the time which should make it extreamly hot like the resivour hooked up to the same lines and i know this makes it sound like a clogged core but i"ve check it and it's got flow and no cracks checked both

now you see why i'm confused and looking for stange things that might be causing this

oh ya ac not working

also have burbed the system several times each time a line has been broken after system has heated up

I dont understand why one of your hoses is cold. Have you taken off the return hose while the engine is running to make sure that the hose has not been blocked off internally? That year there should also be a heater valve on the hose. If there is an uncapped vacuum hose the blend air door will not work as it is vacuum operated and those diaphrams will not work if there is a vacuum leak anywhere in the system. Those earlier years also had two different water pumps available. One clockwise rotation and the other counter clockwise, but that should show up with an engine cooling problem, i.e. running hot at speed. But all being said if there is flow then you should be getting hot water out of both of the heater hoses. Dumb question but is the engine reaching normal operating temp.

blend door is cable ran have seen the cable and lever moving as i adjust temp control

no there is no valve in the lines looks like it was removed before i got it has the t pipes but no valve looks like it was cut off and hose reatached with hose clamp

did answer about pump was wondering about if revese flow being able to keep engine cool or not

and yes temp is running from just below 210 to just above 210 changed stat just to make sure that was not it

and with the resivour getting hot i don't understand why i don't have flow though core that is hooked up to the same hoses

also when i flushed out core to check flow i used the heater hoses to do this just clamped resivour hoses off wile doing this to check hoses at same time

Sorry you are right, vacuum operates modes heater is controled by cable.
I have worked on these things for alot of years and seen alot of things but your jeep does not make sense. The one thing that I cannot grasp is if you have flow both of your lines should be hot, one a little hotter than the other but still hot. You have disconnected the output from the heater core with the engine running and you have output right? You can do this by running a water supply back to the engine through the disconnecte hose.

hey 91sport what engine i didnt see it posted??was looking at the 6cyl it looks to
have 4 hoses to/from.just want to make sure the info is correct.you may want to
put the valve in & back to original set up. or is it a 4cyl??


http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/0a/9d/10/medium/0900c152800a9d10.gif

91 sport, I am far from an expert here, but I read your description of the T's very closely. It seems that what happened at some point is that your heater control valve was replaced with some t's, and rather than cap off the T's, there were hoses that now run into the reservoir (overflow tank).

I'm not sure how that could be rigged without drilling into the reservoir tank, or just keeping the cap open and pushing two hoses into the reservoir.

Anyways, if that is what has actually happened, I would say to remove that end of the T (the part that goes into the reservoir). Based on the way you describe it, you have a parallel flow path for the coolant to completely bypass your heater core (hence no heat in the cabin).

You could remove those hoses that go into the reservoir and cap them off. If you don't have caps or plugs for them, go to a hardware store and get some caps from a garden hose repair kit (which should fit fine), and cap them off.

Might only be a $1, and what you'll basically be doing is finally forcing the coolant through your core.

I post this hesitantly, because I know little compared to most of the guys on here, so if I am off base, someone correct me.

Did anyone consider that maybe the air vents in heater core are clogged. If mice got into the vents and build nests that can block air flow through the heater core and still get some air through it. Also is there flow coming out the heater hose? Just a thought.