Heater core hose setup

dj 480

dj 480

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Original poster
Joined
Jan 30, 2022
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Georgia
Hey guys, a question for the group

Attached are 2 pics of my heater core hoses on my 4.0 in a 97. I am not the original owner and did not do the work. Looks like a bypass of some sort was done to the hoses with a small filter bottle on top. The bottle on top also has a small hose that goes into the firewall around the Drivers side.

Any idea what this setup is or its purpose? I ask as it does not seem to be how it was OEM.

My Jeeps heat works well even though I do not have a slider position for top heat (only feet and defrost)

I appreciate the help on this.

Vr
Dan

the small hose going into the driverside firewall
tempImageL9KY3O.png

The heater core hoses coming out of the firewall (left to right)
tempImagee0z0GY.png
 
TJ4Jim said:
For some reason a vacuum operated shutoff valve was added to interrupt flow.
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What would the benefit be for something like this? Other than when the heater core starts leaking.
 
The compressor looks factory has a different year code. I inferred the original was replaced.
tempImageYDX3qL.png

My controls seem to differ from most with AC as well
tempImageRfIvv1.png
 
TJ4Jim said:
Since the AC system was designed with a full flow heater core there would be no benefit and I doubt the valve would stop any core leak.
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I figured this was done for a reason, and I did not want to remove it and go back to stock without knowing why. The main question I have is the small line that goes into the firewall.
 
dj 480 said:
I figured this was done for a reason, and I did not want to remove it and go back to stock without knowing why. The main question I have is the small line that goes into the firewall.
Click to expand...
Where does it terminate on the otherside of the firewall?
 
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I have a 97 with no A/C, and even if I have both levers from the control panel all the way to the left, heat still escapes into the cab from the vents. I wonder if this was someway to bypass the heater core so you didn’t get that. If it is, I’d be interested in the parts used. It can get miserably hot in the summer while driving. There’s actually no “off” on the fan control so it’s always blowing a little.
 
DaYooperTransplant said:
I have a 97 with no A/C, and even if I have both levers from the control panel all the way to the left, heat still escapes into the cab from the vents. I wonder if this was someway to bypass the heater core so you didn’t get that. If it is, I’d be interested in the parts used. It can get miserably hot in the summer while driving. There’s actually no “off” on the fan control so it’s always blowing a little.
Click to expand...
Sounds like you may have an electrical problem? You should be able to turn the fan completely off.
 
Looks like a GM heater control valve. Somebody just didn't want heat in the cab when the engine was hot and was a GM guy so they put in a valve. Yukon, Suburban 1995-2000 maybe?
 
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The A/c system could be a dealer installed system. The heater control valve function is to remove the heat from the plenum to assist the A/C in cooling better.
 
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