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Unread 12-28-2012, 07:40 AM   #1
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1984 CJ7 
Join Date: Dec 2012
Location: Bloomfield, Ct
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84 cj 7 no heat!!!! Brrrrrr

Hi folks, new to the forum but have referenced this site many times for info. Great resource so thanks! I am stumped!!!!! I just moved from the southwest up to Connecticut and now I actually need heat for the winter! But my heater is not working! I can't find a coolant low diagram to save my life!!!!
The routing of the hoses in my CJ are as follows.....radiator to thermostat, thermostat to intake (front driver side) back of intake (driverside near firewall) across to heater core, heater core back to water pump area on engine...

The hose coming out of the back of in the intake does not get hot at all.... There is coolant flow through the whole system (checked and double checked).. But no heated coolant is flowing to the core.
Some things I've done
- my blower motor works
- all my levers and valves open and close ( interior controls)
- just changed my thermostat yesterday
- topped off coolant and burped the system
- replaced the coolant temperature sensor yesterday
- do not have a heater control valve
- have no leaks and engine doe not overheat! Until I replaced h thermostat h temperature gauge would not get above a smidge above "C". Now it sits in the middle between hot and cold
- took apart the heater core and flushed it. No clogs an gets hot when boiling water s poured thru it ( ouch!)
- webber carb installed last year
- emission modification were done while the jeep was baby sat by another owner so if it is a vacuum problem I could dive into that....

Any suggestion on where to look next. Any additional info on water jackets in the intake as I assume hat is what I'm tackling next. Am I over looking. Sensor or two that im missing?

Brrrrrr freezing in Connecticut!

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Unread 12-28-2012, 08:19 AM   #2
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There shouldn't be any vacuum-based control of heat. My biggest concern would be why the hose from your intake to your heater core isn't getting hot. That says to me there's some serious obstruction in the intake somewhere. But at the same time you said coolant is flowing...out of that hose, I assume? I would try to flush the intake if you can, but removing the hoses at either end and forcing water through the jacket when the intake is cold. Worst case scenario is a cracked jacket and you're leaking into the fuel delivery system, but even then I'd expect some coolant to be moving through?
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Unread 12-28-2012, 08:26 AM   #3
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As a temporary fix, you could bypass the intake. I did it to get more heat from my heater core about 7 years ago, and I haven't changed it back yet. I do live in the desert though, and only need heat about 3 or 4 times a year!! If you do this and get heat, the block (or air bubble) is in the intake, if it stays the same I would say your heater core is rusted/plugged up

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Unread 12-28-2012, 08:30 AM   #4
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You say are putting boiling water in the core and it works and not clogged. After you hook it all up and run it check check the core and see if it just water or coolant mix. Also after you test with boiling water you should blow that out and fill with Coolant so it does not freeze.
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Unread 12-28-2012, 08:33 AM   #5
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Correct me if I'm wrong, but don't the coolant lines to the intake act to cool the intake as well.

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Unread 12-28-2012, 08:35 AM   #6
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1981 CJ8 
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They do, but it's all relative. They keep it from getting too hot, i.e. compatible with engine temperature. That's why you've got a manifold heater - to get the air warm before the heated jacket can take over.
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Unread 12-28-2012, 09:21 AM   #7
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My engine is plumbed like the OP is, and it will roast you in the cab. Ive still got the stock blower motor also. My rear hose gets warm after about 10 minutes of use also.

Get you a temp gun from Napa or auto store, about 50 bucks, shoots a red laser dot, check the temp before the intake, and after and see what the temp drop is, shouldnt be that much difference. Also use the temp gun along all your heater lines and check for a temp drop, thats where the restriction/problem will arise. There should be a temp drop after heater core coming back to the radiator.

Way easier to do this than pull parts and scratch your head.

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Unread 12-28-2012, 11:50 AM   #8
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this may be a stupid reply.On the Air knob do you have it in the half way position?If all the way you go to vent.If you don't have a air knob it could be that also.Maybe the flaps inside the duct aren't moving to the right position for some reason.Does your blower blow some hot air and good air flow
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Unread 12-29-2012, 03:34 AM   #9
John Strenk
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1976 CJ5 
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How did you burp the system?

I had trouble with my heater once because I got the hoses on backwards and it was forcing water into the top of the heater and would not get rid of the air trapped in there.

Another time I had to lift the hoses up to get rid of the trapped air but on that engine I didn't have a water heated manifold.
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