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What thermostat best for Illinois climate?

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Old 03-08-2011, 09:35 PM
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Default 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?
Old 03-08-2011, 09:38 PM
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stock jeeps run the best at 210 just put vents in the hood to keep the rest of it cool
Old 03-08-2011, 10:42 PM
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Just keep the 195 in there. A "cooler" t-stat will do NOTHING good for you.
Old 03-08-2011, 10:42 PM
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The recommended one... 195*
Old 03-09-2011, 04:49 AM
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Originally Posted by Defiance665
The recommended one... 195*
Agreed.

Go with the 195. That is what your 4.0 came with and is the correct application for the vast majority of XJs.
Old 03-09-2011, 09:46 AM
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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".
Old 03-09-2011, 10:14 AM
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Originally Posted by djb383
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; 03-09-2011 at 10:23 AM.
Old 03-09-2011, 10:29 AM
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Originally Posted by djb383
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".
no, but they do mention a 195* thermostat...
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.
Old 03-09-2011, 11:57 AM
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Oh goodie, another t-stat debate!
Old 03-09-2011, 12:03 PM
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Originally Posted by SamSissine2
So what do you think is the applicable thermostat?
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.
Old 03-09-2011, 12:46 PM
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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.
Old 03-09-2011, 12:51 PM
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Originally Posted by djb383
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.
The only time MPG suffers due to a t-stat is when the coolant temperature stays low enough to keep the engine in Open Loop isn't it? What is that, 150 or 160*?

Edit: Just went back to your first post and saw 160*. You already answered my question before I asked lol.
Old 03-09-2011, 01:33 PM
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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".
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