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Quick question about no heat


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1990 4.0L.  No temp to the heater.  Fluids are correct.

 

I still have the little vacuum gizmo on the heater control, but it won't hold a vacuum if it is supposed to.  Should it?  

 

I am willing to replace the heater core, but I would rather replace that gizmo first if it needs it.

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By-pass it and you will be sure that it is out of the equation. (search this site there are a couple of threads including mine on how to do it)

 

Before you take it apart go to the store and get a gallon of vinegar. When you take the hoses off slip them back on in such a way that allows you to fill your heater core totally with vinegar. Let it sit for 10-15 min then flush it with you garden hose (hot water if possible)...repeat 2 or 3 times. now reconnect the hoses by-passing the valve.....heat so good you can weld the holes in your floor pans with it..... :thumbsup:

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That water control valve is the reason the heater core is clogged. It shuts off water flow through the core and every summer the crud builds up eventually clogging it up. The water control valve was removed in 1997 allowing coolant to flow constantly through the core, keeping it clean. Get rid of the valve and plug up the vacuum hose.

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Well that didn't go well.

 

I removed the vacuum gizmo (dremel tool) and flushed the heater core a couple of times using CLR and hot water.   Now hot water goes through the heater core (from the bottom port) and out through the upper port. 

 

From  there it goes into a "T" with one side of the T going to the overflow tank and the other side going back to the engine/water pump.  I don't think I am getting water running back to the water pump for some reason.  I do get hot air out of the heater for about a mintue and then it goes cold again, but I am overheating.    I wonder if  Y would be better than a T.

 

Usually when I dink with the coolant, I just run it up to temp a few times with the overflow cap off and it bleeeds air out of the system that way. 

 

Suggestions?

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Here's something interesting about eliminating the HCV as posted by djb383 on Cherokee Forum.

 

One thing u may want to consider, is removing/eliminating the heater control valve, if you haven't already. '96 down have the HCV, '97 up the Factory eliminated it.
 
During the warm months, with a HCV, (temp lever/knob never moved off cold) coolant sits and stagnates inside the heater core.....There's no fresh coolant/corrosion protection circulation through the heater core.
 
With the HCV removed/eliminated, coolant/corrosion protection flows through the heater core constantly when the motor is running, regardless of where the temp lever/knob is set. 
 
Also, you don't have to remember to turn/slide the heat lever/knob when flushing/re-filling the cooling system because coolant is flowing to/through the heater core when the motor is running and the HCV is absent.
 
Be sure to plug/cap the small vacuum hose when eliminating the HCV.
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Well perhaps it is not fixed.   

 

As I drive down the road for about 1/2 hour at 65, the engine will overheat and start barfing out coolant of the reservior bottle.  There is about 1" of coolant in the reservior bottle when cold

 

I had to tow it to my shop guy since I was not close to home.    Any thoughts about what I should tell him to do?  I figure he will check the thermostat & the water pump. 

 

RIght now my coolant lines go from the engine > "in side" of the heater core > the "out side" of the heater core > the side of the plastic reservoir > out the bottom hole of the reservoir > back to the engine.  Is this the preferred routing?

 

Thanks!

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Sounds like you have air pockets in your cooling system still.

All 4.0L's can be tough to completely fill the cooling system,

especially closed system Renix 4.0L's.

 

Here's what I do;

Park tail down on a slightly sloped driveway,

and fill the radiator & coolant neck via the upper radiator hose connection.

Do this cold, with the heat on full hot (I know you removed the valve, still good practice for the next guy).

Once its full, put the hose on, & bring the rpms to 1800-2000ish for a few seconds to see if some air came to the top (to the hose connection you are filling from).

You might have to do this a few times,

or try a *little* more rpm (not too much tho), or try a steeper slope to park on,

but it should get most of the air out,

eventuality driving the Jeep will get the rest.

 

watch out for the fan while you are doing this!

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Check this out from the FSM

 

This system does not have a radiator pressure cap. Instead the pressure cap is mounted on the coolant pressure bottle. System coolant flows directly through a fully pressurized Hot-Type expansion bottle. Coolant flows through the pressure bottle at all times during engine operation whether the engine is cold or at normal operating temperatures.

 

Larger coolant volume caused by thermal expansion during engine operation is absorbed by the expansion chamber in the bottle. Air trapped in the system is purged through the pressure cap vent valve during maximum coolant expansion..
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Check this out from the FSM
 
This system does not have a radiator pressure cap. Instead the pressure cap is mounted on the coolant pressure bottle. System coolant flows directly through a fully pressurized Hot-Type expansion bottle. Coolant flows through the pressure bottle at all times during engine operation whether the engine is cold or at normal operating temperatures.
 
Larger coolant volume caused by thermal expansion during engine operation is absorbed by the expansion chamber in the bottle. Air trapped in the system is purged through the pressure cap vent valve during maximum coolant expansion..

 

So that's two things wrong with every Renix I've had.....

they don't expel air pockets AND they didn't read the FSM to know they were supposed to do it ;)

sorry Cruiser I couldn't help it :)

 

I've had terrible luck getting any closed system 4.0L to self-purge,

especially reading his earlier post about having heat, then not having heat,

(after removing the valve & flushing the core)

that sounded like low coolant/air pockets to me.

 

Either way, good luck,

I hope you figure it out,

overheating in December is no fun.

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I relayed the coolant burping and cap number information to "my guy".   We shall see how that goes.  They are pretty good over there.

 

I was pretty sure I had the system pretty well burped as to not trap any air in there.  I agree though that it is a tough system to burp completely.

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http://www.amazon.com/gp/aw/d/B000C7S062 Spectra Premium CU1193. Its what I got when I did an open cooling swap this summer. Has the bung and it keeps the truck cool even in high heat (Took 15 minutes to turn on the AUX fan at idle during a 100 degree day in Alabama) and best part? Amazing price with free shipping! Hope this helps :D
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