What size thermostat?
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Joined: Feb 2010
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From: central michigan
Year: 1997
Model: Cherokee
Engine: 4.0
What size thermostat?
Im having a minor cooling issue. My jeep is running a bit warm and im gonna replace the thermostat since there is not one in it. i am also gonna pick up a water pump but i was told i should run a 190 or 195 thermostat. what should i run?
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From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
195 is stock t stat...i run a 180 in the summer to keep it cooler....
CF Veteran
Joined: Jan 2010
Posts: 1,316
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From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
id run a 180* then...some say it will kick you into an open loop due to the engine not reaching the pre-designated operating temp, therefore dumping more fuel. ive done enough research to know this isnt true and plugged my junk into a scantool at school to prove it.
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From: Alexander City, alabama
Year: 1996
Model: Cherokee
Engine: 4.0 HO
Correct me if I'm wrong but I swear I read somewhere that running a lower degree stat is actually not that great for these 4.0s. Bitim not an expert. Insert professional info >here<
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Joined: Jan 2010
Posts: 1,316
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From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
lol as stated above......looking for the thread now...
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CF Veteran
Joined: Jan 2010
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From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
Correct me if I'm wrong but I swear I read somewhere that running a lower degree stat is actually not that great for these 4.0s. Bitim not an expert. Insert professional info > We use a ScanGauge in our '98 XJ and the system goes into "closed loop" in less than a minute after start-up, even on the coldest of mornings. Coolant temp has virtually nothing to do with "open/closed loop". It's the temp of the O2 sensor that determines when the system goes into "closed loop" and heated O2 sensors close the loop very quickly for good engine performance and low emissions even on a cold engine.
The ScanGauge shows coolant temp between 197F and 204F with a factory 195F t-stat installed in our XJ. After installing a 180F t-stat, coolant temp ranges from 180F to 188F with no effect/change on mpg (mid teens mpg in town, low 20's mpg hwy). <
The ScanGauge shows coolant temp between 197F and 204F with a factory 195F t-stat installed in our XJ. After installing a 180F t-stat, coolant temp ranges from 180F to 188F with no effect/change on mpg (mid teens mpg in town, low 20's mpg hwy). <
refer to this thread
https://www.cherokeeforum.com/f2/i-w...ne-temp-40057/
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Joined: Apr 2010
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From: Greenville, SC
Year: 1996 two-door SE
Model: Cherokee
Engine: 4.0
According to the chapter on fuel systems in the 1997 Jeep Cherokee factory service manual about open and closed loop:
“ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warmup, the powertrain control module (PCM) receives inputs from:
Battery voltage
Crankshaft position sensor
Engine coolant temperature sensor
Intake manifold air temperature sensor
Manifold absolute pressure (MAP) sensor
Throttle position sensor (TPS)
Camshaft position sensor signal (in the distributor)
Park/neutral switch (gear indicator signal—auto.
trans. only)
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)…
When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.
IDLE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the powertrain control module (PCM) receives inputs from:
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)
Battery voltage
Crankshaft position sensor
Engine coolant temperature sensor
[Etc.]…
CRUISE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the powertrain control module (PCM) receives inputs from:
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)
Battery voltage
Engine coolant temperature sensor
[Etc.]”
The manual doesn't say exactly what "operating temperature" is, and I don't believe everything I read, but I do believe that coolant temperature is inputted to the PCM before going into and during closed loop operation.
“ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warmup, the powertrain control module (PCM) receives inputs from:
Battery voltage
Crankshaft position sensor
Engine coolant temperature sensor
Intake manifold air temperature sensor
Manifold absolute pressure (MAP) sensor
Throttle position sensor (TPS)
Camshaft position sensor signal (in the distributor)
Park/neutral switch (gear indicator signal—auto.
trans. only)
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)…
When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.
IDLE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At idle speed, the powertrain control module (PCM) receives inputs from:
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)
Battery voltage
Crankshaft position sensor
Engine coolant temperature sensor
[Etc.]…
CRUISE MODE
When the engine is at operating temperature, this is a Closed Loop mode. At cruising speed, the powertrain control module (PCM) receives inputs from:
Air conditioning select signal (if equipped)
Air conditioning request signal (if equipped)
Battery voltage
Engine coolant temperature sensor
[Etc.]”
The manual doesn't say exactly what "operating temperature" is, and I don't believe everything I read, but I do believe that coolant temperature is inputted to the PCM before going into and during closed loop operation.
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Joined: Jan 2010
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From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
im not arguing about this.
i run a 180* t stat and have put my junk on scantools and a diagnostic computer to monitor the open/closed loop of the fuel system on warmup and have seen for myself that it goes into closed loop after about a minute of operation just like it did with the 195* t stat. i agree that coolant temp is inputed into the PCM, but as you posted it SOLELY does not control whether the PCM goes into open or closed loop.
it could be different for you as the emmissions changed in 1998 to include the O2 sensors in the open/closed loop system, but i KNOW that the 180* t stat does not affect going into closed loop operation in my application.
i run a 180* t stat and have put my junk on scantools and a diagnostic computer to monitor the open/closed loop of the fuel system on warmup and have seen for myself that it goes into closed loop after about a minute of operation just like it did with the 195* t stat. i agree that coolant temp is inputed into the PCM, but as you posted it SOLELY does not control whether the PCM goes into open or closed loop.
it could be different for you as the emmissions changed in 1998 to include the O2 sensors in the open/closed loop system, but i KNOW that the 180* t stat does not affect going into closed loop operation in my application.
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Joined: Dec 2009
Posts: 224
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From: Southern California
Year: 1988
Model: Cherokee
Engine: 4.0
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Joined: May 2010
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From: southlake, TX
Year: 1996 Sport
Model: Cherokee
Engine: 4.0L H.O.
i've been running 190 in mine for ever....better than stock....but not overkill....however, you also should upgrade your water pump (with a better turbine and to handle higher volume) and your radiator hoses...keep rad fluid in check and eventually drop in a 3-row radiator....
....also, wrap the battery in a heat resistant blanket - it'll work better and last longer (or move it to the back!)....
....next oil change, tellem to use FRAM HP1 or the Mopar Hi-Performance oil filter...it has a larger capacity = more oil = more engine protection....and synthetic oil will help too.
....also, wrap the battery in a heat resistant blanket - it'll work better and last longer (or move it to the back!)....
....next oil change, tellem to use FRAM HP1 or the Mopar Hi-Performance oil filter...it has a larger capacity = more oil = more engine protection....and synthetic oil will help too.
CF Veteran
Joined: Jan 2010
Posts: 1,316
Likes: 1
From: Coeur d' Alene, Idaho
Year: 1998
Model: Cherokee
Engine: 4.0 rebuilt w/ bored TB, banks header, upgraded ignition, 3 row rad, high flow h2o pump, 180* t-stat
i've been running 190 in mine for ever....better than stock....but not overkill....however, you also should upgrade your water pump (with a better turbine and to handle higher volume) and your radiator hoses...keep rad fluid in check and eventually drop in a 3-row radiator....
....also, wrap the battery in a heat resistant blanket - it'll work better and last longer (or move it to the back!)....
....next oil change, tellem to use FRAM HP1 or the Mopar Hi-Performance oil filter...it has a larger capacity = more oil = more engine protection....and synthetic oil will help too.
....also, wrap the battery in a heat resistant blanket - it'll work better and last longer (or move it to the back!)....
....next oil change, tellem to use FRAM HP1 or the Mopar Hi-Performance oil filter...it has a larger capacity = more oil = more engine protection....and synthetic oil will help too.