Is the larger or smaller heater hose going to thermostat housing?

Stinger

Stinger

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The 4.0 has two hoses going to the firewall. One is larger than the other. Going to flush my cooling system and I need to splice into the heater intake hose. This hose goes to the top of the 4.0 However, in my case both hoses dive down and under interning the thermostats housing almos together.
So please somebody take a look for me. Is it the larger or smaller going to the thermostat housing on top of the engine?
Thanks
 
this ^^

Heater takes hot water direct from the engine. The top rad hose is the return line to the rad. The bottom hose returns cooled? water to reheat thru the engine before cycling thru the heater again.

NB an engine warms up faster if you shut off the heater... which is basically another rad, cooling the coolant.
 
Last edited:
Great answers but they don't answer the mail. Is the smaller or larger hose on top?
 
Which one small or large goes to the thermostat hoIusing on the 4 liter?
 
The larger return hose from the thermostat housing connects to the bottom port on the firewall.

Heater Hoses.JPG
 
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Guessed so. I have the FSM for my TJ, but haven't dug through it much yet. What's up with the MOPAR parts manual? What does it do that the FSM doesn't?
 
Thanks Jerry. I looked at length in my FSM and did not see that page. What page number is it?
 
From the top of my thermostat housing the tube goes to the top port of the firewall. In the FSM it goes to the bottom port on the firewall. Any ideas why this would be? Maybe the previous owner connected it backwards?? I just picked up this jeep 2003 rubicon and have been following this forum trying to get fluids tuned up first and for most. Working on following the radiator flush thread today.
I appreciate the help!

image.jpg
 
Black-Bear said:
From the top of my thermostat housing the tube goes to the top port of the firewall. In the FSM it goes to the bottom port on the firewall. Any ideas why this would be? Maybe the previous owner connected it backwards?? I just picked up this jeep 2003 rubicon and have been following this forum trying to get fluids tuned up first and for most. Working on following the radiator flush thread today.
I appreciate the help!

View attachment 136444
Click to expand...
The drawing also shows the top hose on the right side, but in fact the top hose is offset left....
 
Ya hmm... I’m pretty noob mechanic, was really needing to which is the inlet so I could splice the flush kit tee into the correct hose. I’m not sure if it really matters anywho. I got the radiator drained and block plug pulled pretty easily. glad I’m doing this, the fluid is motor oil black :eek:.

I think I’ll just pull off both hoses run water thru the core until it runs clear (rather than splicing one at this point)

still curious if it’s setup wrong if anyone has some advice. Heat works fine and engine runs cool. so maybe I don’t have a problem
 
Black-Bear said:
Ya hmm... I’m pretty noob mechanic, was really needing to which is the inlet so I could splice the flush kit tee into the correct hose. I’m not sure if it really matters anywho. I got the radiator drained and block plug pulled pretty easily. glad I’m doing this, the fluid is motor oil black :eek:.

I think I’ll just pull off both hoses run water thru the core until it runs clear (rather than splicing one at this point)

still curious if it’s setup wrong if anyone has some advice. Heat works fine and engine runs cool. so maybe I don’t have a problem
Click to expand...
If you cut the hose and put in a splice for flush it will fail at some point. (Naturally) Mine failed a few years after installing. No matter how hard I tried, I couldn't seal it correctly. Maybe the splice was deteriorating or was warping due to the coolant heat. In my research, I saw the same thing with others. It's good to flush the cooling system and heater core. Just buy a new hose ($15-$20) and install it when you're done as you won't need to flush again for a long time. Just my 2 cents.
 
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