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Old 11-14-2015, 09:15 PM
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Leaking problem after replacing thermostat....

This might be covered long time ago, however could not find one in specific....

I just changed my thermostat T-Stat 185 degrees because a P0128 code, it took me and my friend around 5 hours. What a pain in the butt for such a simple task, The designed of the sitting of the thermostat is terrible because is vertical and don't hold the T in position. Took three times after the thermostat didn't sat correctly and cut it the gasket.

After the 3rd try it steal sweep and we tight the bolts a little more. I didn't leak then so we finished filling the cooling system. Went on a road test and at some point during swept a little bit and the Temp Gauge now is reading dead on 210 degrees. Before the T-change the Jeep have never reach close to 210 during my 45 minutes commute in 80 degree weather. Today by the time we finished was in the 50s.

I'm just frustrated with this Jeep, beside a Rotary Engine is the most difficult vehicle to work on for any simple task. Must be the design....

Newb help!!!

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Old 11-15-2015, 04:50 AM   #2
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i found that mine leaked without any sealant on both sides of the gasket. i learned the hard way with the waterpump as well. never again without any sealant. 210 is normal, mine sits at around 195-200ish, 215 up-hill sometimes.

at most, try sanding the flange surface of the thermostat housing on a mirror or pane of glass with a fine grit. i use to do this with the cylinder head for my jetski back in the day. circular motion is the key, wax-on-wax-off =) but thermostat RTV sealant works for the most part.

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Old 11-15-2015, 07:33 AM   #3
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Yea throw a little rtv on there.

As for the temp issue, did your thermostat have a hole at the top to vent trapped air? Mopar ones do and many drill a small hole in the same location on the ones that didn't to ensure no air is trapped back there which could be the case of your higher than normal reading right now
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Old 11-15-2015, 07:55 AM   #4
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210 is not high. It must have been lower than normal before.
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Old 11-15-2015, 08:33 AM   #5
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Originally Posted by Paposalsa View Post
This might be covered long time ago, however could not find one in specific.... I just changed my thermostat T-Stat 185 degrees because a P0128 code, it took me and my friend around 5 hours. What a pain in the butt for such a simple task, The designed of the sitting of the thermostat is terrible because is vertical and don't hold the T in position. Took three times after the thermostat didn't sat correctly and cut it the gasket. After the 3rd try it steal sweep and we tight the bolts a little more. I didn't leak then so we finished filling the cooling system. Went on a road test and at some point during swept a little bit and the Temp Gauge now is reading dead on 210 degrees. Before the T-change the Jeep have never reach close to 210 during my 45 minutes commute in 80 degree weather. Today by the time we finished was in the 50s. I'm just frustrated with this Jeep, beside a Rotary Engine is the most difficult vehicle to work on for any simple task. Must be the design.... Newb help!!!
isnt it supposed to be a 195 degree thermostat?
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Old 11-15-2015, 10:33 AM   #6
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isnt it supposed to be a 195 degree thermostat?
Yes, 195F non-failsafe. Stant or Mopar would be my only choice
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Old 11-15-2015, 10:34 AM   #7
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A 195 degree thermostat starts to open at 195. It is also important to understand that the function of the thermostat is to maintain a minimum temperature.
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Old 11-15-2015, 11:21 AM
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The Thermostat that I bought is a non-fail safe Stant Sperstat (195ºF) that has like and oval shape instead of a drill hole, recommended by most. For what a read that will function as vent that is why I didn't drill a hole.

Well the main issue is the thermostat not staying in place and cutting the gasket. The way the thermostat sits in the vertical position any minimal touch by the thermo housing will slide it off the small grove.

I'm going to check it this morning even that it was cold overnight to see if the RTV sealant cure and it doesn't leak. Also check the bolts because my friend snug them pretty good. If not back to square one with the thermo, gasket, etc.

Might buy a new MOPAR Thermostat, gasket and even a new thermo housing. Since some people suggested that if the bolts were over tighten it might warp the housing causing not to sit straight against the block.....

NOTE: Something strange is that my friend that took the bolts off told me that the bottom bolt(small) was not tight but it wasn't leaking
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Old 11-15-2015, 11:33 AM   #9
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Also check the bolts because my friend snug them pretty good.
156 in/lbs is the specified torque for the thermostat housing.
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Old 11-15-2015, 01:01 PM   #10
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A 195 degree thermostat starts to open at 195. It is also important to understand that the function of the thermostat is to maintain a minimum temperature.
Exactly. A lower temp thermostat can't magically cause an engine to run cooler except in cold ambient conditions. A non-failsafe 195 degree thermostat is the correct thermostat for our TJ engines.
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Old 11-15-2015, 02:47 PM   #11
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And Jerry's posts told me to make certain the mating surfaces were spotless and to use a paper gasket with no sealants. Everyone with a garage that has motors and wrenches in it should have a sheet of paper gasket material in a drawer. It worked perfectly. Goo will seal a bad joint, for a while IME.
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Old 11-15-2015, 03:29 PM
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Well I checked the Jeep and the thermostat still has a small leak plus the Temp goes up to 210 in no time.

Some people said use sealant others said don't use it. The housing warp, the type of thermostat, type of gasket......????????

I'm beyond mad and confused right now....for something simple to be this complicated.

I have replaced many thermostat on other vehicles with no problems at all ...
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Old 11-15-2015, 03:50 PM   #13
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Yes, it will go up to 210 on non-cold days even with an incorrect lower temperature model thermostat installed. It's on cold days where the engine will take longer to warm up and not get fully up to temp if the wrong (lower than 195 degree) model thermostat is installed. Again, your thermostat should be a non-failsafe 195 degree model, like Stant's Superstat. Pay no attention to anyone clueless enough to recommend a lower than 195 degree thermostat on a TJ.

Leaks are most commonly caused by not having thoroughly cleaned off both gasket seating surfaces. They need to be absolutely spotless which pretty much means use a small wire brush on them to get all of the old gunk off. ANYTHING left behind will cause a leak.

Use the gasket only, do not use RTV. The factory doesn't need RTV to get a leak-free cooling system, neither do we.
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Old 11-15-2015, 03:52 PM   #14
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I run a 185 T on my 99. No issues at all. I used a generic gasket that came with the new T. Just make sure to clean the old gasket off with a wire brush, razor blade or sand paper.
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Old 11-15-2015, 03:57 PM   #15
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I run a 185 T on my 99.
The factory specifies a 195, there is no upside to using a colder than specified thermostat. There are downsides though, it will take the engine longer to warm up on really cold days and it may not get warm enough for the engine to get fully up to temp. And with our engine computers being programmed around a 195 degree thermostat, the engine may not get warm enough to get out of open loop operation which will mean the 02 sensors are being ignored which means the engine will run too rich.
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Old 11-15-2015, 04:12 PM   #16
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I went to the auto parts store to get a replacement for the old one. I got the 185 because I didnt know until after about the 195.... Long story short. Ive never had an issue, so I kept it. Yeah sure it takes longer to warm up in the morning but Im in SO CAL. It doesnt get colder than 55 at night here. My normal op temp... You guessed it, still around 210. Cold mornings its at 205ish and warm afternoons its 215ish.
Unless there is an issue that I dont know about, Ill keep it.
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Old 11-15-2015, 04:16 PM   #17
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And with our engine computers being programmed around a 195 degree thermostat, the engine may not get warm enough to get out of open loop operation which will mean the 02 sensors are being ignored which means the engine will run too rich.
Good to know though, something good to learn in case I develop any issues in the future.
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Old 11-15-2015, 06:05 PM
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To me since we try it 3 times, the 2 times we removed the housing the thermostat has cut the gasket with and without Adhesive/RTV because it is not stating in the groove during installation.

Or the housing might be warp because both mating surfaces were cleaned real good....
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Old 11-15-2015, 07:45 PM   #19
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Stick the thermostat in place with a few drops of Superglue before you install the gasket and housing.
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Old 11-15-2015, 09:45 PM   #20
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There are downsides though, it will take the engine longer to warm up on really cold days and it may not get warm enough for the engine to get fully up to temp. And with our engine computers being programmed around a 195 degree thermostat, the engine may not get warm enough to get out of open loop operation which will mean the 02 sensors are being ignored which means the engine will run too rich.
Just FYI. My Scangauge can monitor open-closed loop. I've watched it an the temp it switches varies so it is no just temp. The temp it switches is far below 195. I have seen it as low as 100 F.
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Old 11-15-2015, 10:06 PM   #21
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Just FYI. My Scangauge can monitor open-closed loop. I've watched it an the temp it switches varies so it is no just temp. The temp it switches is far below 195. I have seen it as low as 100 F.
You are absolutely correct. But that won't stop the misinformation from being repeated over and over. Some folks just believe what they want to believe and want to make sure that everyone else who doesn't know better believes it, too.

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