heat prob for expert not heat have checked a lot

[91sport]

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 ?????

[fredjacksonsan]

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.

[91sport]

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

[rhandwor]

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

[fredjacksonsan]

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.

[hundahunta]

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...

[inafogg]

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

[rhandwor]

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.

[DIVERHERB]

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.

[91sport]

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.)

[91sport]

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

[91sport]

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

[inafogg]

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??

[rhandwor]

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.

[hundahunta]

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