What thermostat best for Illinois climate?
Thread Starter
Seasoned Member
Joined: Aug 2008
Posts: 425
Likes: 0
From: Illinois
Year: 1998
Model: Cherokee
Engine: 4.0L I6
What thermostat best for Illinois climate?
It can be 100+ in the summer and -20 or colder in the winter. What temp. thermostat would y'all recommend?
CF Veteran
Joined: Nov 2010
Posts: 5,841
Likes: 117
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
Nowhere in the FSM is the word "recommended" and the number "195F" used in the same sentence......and nowhere in the FSM does it say "Jeeps run the best at 210F". It does say "a warm-up cycle is counted when coolant temp has crossed 160F". The FSM goes on further to say "Caution: do not operate an engine without a thermostat". It does not say "do not operate the engine with any t-stat other than a 195F".
Seasoned Member
Joined: Jan 2011
Posts: 313
Likes: 0
From: Charlotte, NC
Year: 2001
Model: Cherokee
Engine: 4.0
Nowhere in the FSM is the word "recommended" and the number "195F" used in the same sentence......and nowhere in the FSM does it say "Jeeps run the best at 210F". It does say "a warm-up cycle is counted when coolant temp has crossed 160F". The FSM goes on further to say "Caution: do not operate an engine without a thermostat". It does not say "do not operate the engine with any t-stat other than a 195F".
So what do you think is the applicable thermostat?
Last edited by SamSissine2; Mar 9, 2011 at 10:23 AM.
Trending Topics
CF Veteran
Joined: May 2009
Posts: 10,438
Likes: 73
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
Nowhere in the FSM is the word "recommended" and the number "195F" used in the same sentence......and nowhere in the FSM does it say "Jeeps run the best at 210F". It does say "a warm-up cycle is counted when coolant temp has crossed 160F". The FSM goes on further to say "Caution: do not operate an engine without a thermostat". It does not say "do not operate the engine with any t-stat other than a 195F".
97 FSM
THERMOSTAT
A pellet-type thermostat controls the operating
temperature of the engine by controlling the amount
of coolant flow to the radiator. On all engines the
thermostat is closed below 195°F (90°C). Above this
temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warm-up and overall
temperature control.
An arrow plus the word UP is stamped on the
front flange next to the air bleed. The words TO
RAD are stamped on one arm of the thermostat.
They indicate the proper installed position.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: longer engine warm-up time, unre-
liable warm-up performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
CAUTION: Do not operate an engine without a
thermostat, except for servicing or testing.
A pellet-type thermostat controls the operating
temperature of the engine by controlling the amount
of coolant flow to the radiator. On all engines the
thermostat is closed below 195°F (90°C). Above this
temperature, coolant is allowed to flow to the radia-
tor. This provides quick engine warm-up and overall
temperature control.
An arrow plus the word UP is stamped on the
front flange next to the air bleed. The words TO
RAD are stamped on one arm of the thermostat.
They indicate the proper installed position.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes other prob-
lems. These are: longer engine warm-up time, unre-
liable warm-up performance, increased exhaust
emissions and crankcase condensation. This conden-
sation can result in sludge formation.
CAUTION: Do not operate an engine without a
thermostat, except for servicing or testing.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
It doesn't matter what "I think". The XJ left the factory with a t-stat
that is closed below 195F as stated in the FSM, BUT........a 180F t-stat IS available from Jeep/Chrysler.
My point is, the word "recommended" is NOT used and 210F is NOT referred to as "best" anywhere in the FSM........but they get repeated over, and over, and over again in forums.
that is closed below 195F as stated in the FSM, BUT........a 180F t-stat IS available from Jeep/Chrysler.
My point is, the word "recommended" is NOT used and 210F is NOT referred to as "best" anywhere in the FSM........but they get repeated over, and over, and over again in forums.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
He Defiance, I'm glad u posted that segment from the FSM because one more item that the FSM does NOT state is "lower mpg if u don't use a 195F t-stat"......yet it's repeated on forums over, and over, and over again.
CF Veteran
Joined: Oct 2009
Posts: 2,867
Likes: 16
From: Fauquier County, Virginia
Year: 1991
Model: Cherokee
Engine: I-6 4.0 HO
Edit: Just went back to your first post and saw 160*. You already answered my question before I asked lol.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
The system enters "closed loop" way before coolant temp reaches 160F. When the O2 sensor(s) reach operating temp (600F-650F) and start sending a signal to the ECM, at that point, the loop closes. The "loop" consists of basically 3 parts/areas.......the engine, the ECM, and the O2 sensor(s). At cold start-up, the loop is open....the engine is running on pre-programmed maps in the ECM. When the O2 sensor(s) kick in, the loop is considered closed. That's a basic/general description of open loop/closed loop.....it gets complex from there.
When this pic was snapped, coolant temp was only 94F but the system had entered "closed loop".
When this pic was snapped, coolant temp was only 94F but the system had entered "closed loop".
Thread
Thread Starter
Forum
Replies
Last Post
jmsummers2012
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
56
Jun 12, 2025 02:04 AM
cpnwrench
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
14
May 5, 2024 12:21 PM
villamagna71
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
2
Sep 28, 2015 12:05 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)