205' Thermostat - JeepForum.com
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post #1 of 18 Old 10-21-2021, 12:04 PM Thread Starter
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205' Thermostat

Hi guys,


Time for me to start a thread. So my 1994 ZJ has been towing stuff for years and in justa week I have learned more than in the 23 years. So thank you.


So what I have learned, The stock fan sucks, The Stock clutch fan re engages at a really high temp (230'f).



I have been towing for years and suffering with bad cooling due to stock fan and fan clutch despite my installing a cooler thermostat and a big dual core aluminum radiator. At 230'F the AC hardly works at all.



So I have done Desertriders fan and fan clutch upgrade (thank you) but I am up against design limitations of the 195' thermostat - it first opens at 160'F and when ambient is cool it stays at 160'F which is makes the ECU think the engine is running too cool (it is).


So my question is at what temp the 205'F thermostat first opens? I'm assuming it will be higher than the 195'F thermostat and I'm assuming that my big radiator will keep the engine at that temp unless I put a big load on it (Tow) or operate in high ambient temps.


Or I may go back to the single row radiator and the 195'F thermostat.

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post #2 of 18 Old 10-24-2021, 08:38 PM
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I have never seen a 195 degree F T-stat open at 160 degrees? The ones I have tested in water on the stove open up at 195F and are fully open at 215F. ( professional digital thermometer)

I'm not sure what is going on with your t-stat in the Jeep but as you pointed out 160 is too cold for it to be open.

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post #3 of 18 Old 10-25-2021, 01:48 PM Thread Starter
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Yeah. Thanks got me thinking and I went out and put my digital thermometer on the upper hose and on the fittings around the thermostat and WALLA it reads about 195.



So I think my problem is an inaccurate temperature sender. Just to the left of the TStat and the heater hose? Looks like I'm going to make a mess again.
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post #4 of 18 Old 10-25-2021, 04:02 PM
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With the engine cold,and the pressure released in the cooling system,you won't loose a lot of coolant. I would wrap the threads of the new sensor with Teflon tape and have it ready to go into the hole of the bad sensor. It will reduse the coolant loss.

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post #5 of 18 Old 10-25-2021, 04:45 PM
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On a 94 there are two sensors. One for the ECM and one for the gauge. On the 4.0 the gauge sensor is on the rear driver side of the cylinder head. On the V8, I believe, the sensors are on either side of the thermostat. Looks like the passenger side is the gauge sensor. Ignore the highlight on the one pic below. It's just what I was able to find quickly.
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post #6 of 18 Old 10-25-2021, 05:04 PM
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My 94 4.0 also shows low on the dash gauge. I replaced the tstat with a mopar unit, no change... Replaced the sender with a mopar unit, no change. The PCM shows the engine running at 200F, my IR gun shows it running at 200F, only thing I can figure is the gauge is no longer accurate or it gets a cooler reading since its at the back of the head.

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post #7 of 18 Old 10-26-2021, 09:19 AM Thread Starter
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zjosh93 - Thanks. I bought a sensor but it doesn't look like the right one. The one in the head looks smaller than the NAPA one I got. The NAPA one is single wire. Hummm more reading.


Might also could be a ground wire to the instrument display causing a problem?
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post #8 of 18 Old 10-26-2021, 09:27 AM
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Following. I have the 5.2 but I have not done the thermostat yet. My gauge reads about 208 once it is fully warmed up. I was thinking of switching it to a 180 tstat which I have. I maybe rethinking all this as well. Mine is just a try rig, so I was looking at keeping it running cooler.

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post #9 of 18 Old 10-26-2021, 09:39 AM
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Since the sensor and gage both work on resistance ( ohms ) i would pull the instrument cluster and clean all plugs / receps with a spray ELECTRONIC cleaner.
Any increase in resistance will cause the gage to improperly read the true temp.

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post #10 of 18 Old 10-26-2021, 11:09 AM Thread Starter
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205'F Thermostat?

Rapidrob - Yes. Changing the Coolant sensor (Gauge) changed nothing. Still kicks down at 160'f while my digital thermometer indicates 194'F at the metal around the base of the sensor. I've got some Wurth Electrical Contact cleaner so I will pull the Instrument cluster and clean the contacts.

Is there a frame ground somewhere I need to remove clean and reinstall?
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post #11 of 18 Old 10-26-2021, 11:17 AM Thread Starter
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BTW - Shoutout to Barricade Garage on Youtube. He has been spot on with his ZJ videos. Great stuff.


ALSO dumb noob question: How do I edit something I've already posted on this forum?
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post #12 of 18 Old 10-26-2021, 01:05 PM
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Usually a bad ground would cause a swinging meter up / down on display or no display at all.
A dirty plug or corroded wire would be my first eyeball.

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post #13 of 18 Old 10-26-2021, 01:18 PM
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Quote:
Originally Posted by ZJ Still Runs View Post
BTW - Shoutout to Barricade Garage on Youtube. He has been spot on with his ZJ videos. Great stuff.


ALSO dumb noob question: How do I edit something I've already posted on this forum?
There is an edit icon at the bottom of each of your posts. It is where the quote icon is on other members posts.

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post #14 of 18 Old 10-26-2021, 02:53 PM Thread Starter
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crikey

Quote:
Originally Posted by GOLDWING View Post
There is an edit icon at the bottom of each of your posts. It is where the quote icon is on other members posts.

Not on my posts. And then the fine print in the box labeled "Posting Rules" it says I'm not allowed to edit my post. Why?


Reading up on removing the instrument cluster....
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post #15 of 18 Old 10-27-2021, 10:18 AM
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IIRC after you post you have (I think) like 30 min. to edit your post. After that it's set in stone.


Yup, just checked the edit button is right next to the quote button. Pretty sure it's 30 min. time limit.

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Last edited by MaintMech; 10-27-2021 at 10:20 AM. Reason: Checking...
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