2 questions 1 thread, please advise.
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
The thermostat regulates engine outlet temperature (to the radiator)
Coolant flows through the heater system at all times, regardless if the thermostat is open or closed. It also circulates from the head back to the block via this bypass at all times.
I am running a 195* thermostat.
When the engine is warmed up, and I'm driving in stop/go traffic in town, it runs around 205-210*.
When I'm on the highway, and it's cold outside, it runs somewhere around 175-180* (I'm sure once the coolant that circulates back toward the front of the engine heats back up to around 195-200* by the time it reaches the thermostat again) Probably why Jeep put the engine coolant temp sensor in the thermostat housing.
When I'm wheeling a trail, and crawling up a mountain, it runs somewhere around 225-230*
I don't worry at all at that temp because it never gets up near the red zone, and always comes back down once the electric fan has been on for a little while.
One thing that I'm confused about.
In the other thread that Crazy 8 posted. The OP mentions something about "all 99 are Reverse"
I'm not quite sure what that poster was referring to?
As far as I know, all 4.0 engines are cooled the same, minus the difference between the Renix, and HO overflow systems of course..........
Coolant flows through the heater system at all times, regardless if the thermostat is open or closed. It also circulates from the head back to the block via this bypass at all times.
I am running a 195* thermostat.
When the engine is warmed up, and I'm driving in stop/go traffic in town, it runs around 205-210*.
When I'm on the highway, and it's cold outside, it runs somewhere around 175-180* (I'm sure once the coolant that circulates back toward the front of the engine heats back up to around 195-200* by the time it reaches the thermostat again) Probably why Jeep put the engine coolant temp sensor in the thermostat housing.
When I'm wheeling a trail, and crawling up a mountain, it runs somewhere around 225-230*
I don't worry at all at that temp because it never gets up near the red zone, and always comes back down once the electric fan has been on for a little while.
One thing that I'm confused about.
In the other thread that Crazy 8 posted. The OP mentions something about "all 99 are Reverse"
I'm not quite sure what that poster was referring to?
As far as I know, all 4.0 engines are cooled the same, minus the difference between the Renix, and HO overflow systems of course..........
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It doesn't leak any fluid, and I know it's working cause I can hear the fan over the engine noise..............But its old.
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
What brand stat did you put in?
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From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
Geez.....that beamer still has pistons swappin' holes.
The fan clutch in that goofy video is 100% shot......0% effective. If it was say 50%-60% shot, or 40%-50% effective, it would completely shred that new paper instantly, thus appearing to be in good shape by that worthless test because it shred the paper. Again, it would still only be 40%-50% effective at pulling max air thru the rad when needed. Do u want a fan clutch that is only 40%-50% effective but will shred a newspaper?......I don't. To me, a $35 fan clutch is a disposable maintenance item.
The fan clutch in that goofy video is 100% shot......0% effective. If it was say 50%-60% shot, or 40%-50% effective, it would completely shred that new paper instantly, thus appearing to be in good shape by that worthless test because it shred the paper. Again, it would still only be 40%-50% effective at pulling max air thru the rad when needed. Do u want a fan clutch that is only 40%-50% effective but will shred a newspaper?......I don't. To me, a $35 fan clutch is a disposable maintenance item.
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Joined: Nov 2009
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From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
.......and if the heater control valve is closed, thus blocking flow to the heater core, the bypass loop is still flowing coolant thru the motor by bypassing the heater control valve.
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Joined: Apr 2009
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Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
Coolant does not flow through the heater core at all times when the engine is running, assuming the system has a working heater water control valve.
Last edited by Firestorm500; Nov 25, 2014 at 11:28 AM.
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Joined: Nov 2009
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From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
For once, u agree with me. LOL
If we could just get someone else to understand how the XJ cooling system flows and how the 2 coolant flow "loops" work and what the stat does.
If we could just get someone else to understand how the XJ cooling system flows and how the 2 coolant flow "loops" work and what the stat does.
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Joined: Sep 2014
Posts: 896
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From: Phoenix, A-to-Z
Year: 1988
Model: Cherokee
Engine: 4.0
In my Jeep, the heater core is bypassed by looping the out hose right back in. It rarely gets cold enough in Phoenix to use the heater. The PO had routed the hose like that and I haven't yet tested the heater core to see if it is leaking or blocked up... One of these days I will though it really doesn't matter cus I am not going to need to use the heater.
TBH, the PO totally hacked up the cooling system ghetto-style, but it works and I don't have the scratch to fix it just yet.
(I have found employment, but I don't start until the 8th of Dec. The job pays enough that I can hook up the Jeep right and make it stylin', but it will be a few more weeks...)
Last edited by Crazy 8s; Nov 25, 2014 at 12:34 PM.
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I was referring to the heater loop in general.
On the later models it goes through the heater at all times.
On the '96-earlier ones, it gets bypassed at the heater valve, and just loops back to the engine from there.
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Joined: Nov 2009
Posts: 8,172
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From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
Coolant is never blocked from flowing inside/thru the block/motor. Coolant flows thru the motor, via the bypass loop, all of the time the motor is running. Coolant flow thru the radiator loop is anywhere from none to a lot. Coolant flow is NEVER closed/shut-off thru the motor, however coolant flow can be, and is quite frequently, shut-off to the radiator.
Also, congratulations on the new job.
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The standard thermostat design has to force itself open against the direction of coolant flow............I guess in some instances it can have an affect on the way it tries to open at the proper temperature.
The "Balanced Flow" style is designed so that it has equal pressure on both sides of the actual valve that opens..............
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Joined: Aug 2011
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
http://forums.corral.net/forums/5-0-...ood-story.html
http://www.corvetteforum.com/forums/...ats-p-o-s.html
Last edited by cruiser54; Nov 25, 2014 at 04:05 PM.