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Farticcus of Plenticcus
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Discussion Starter #1
A few years ago, when I was doing research for the 160* t-stats, I also had thought of using 170* t-stats for those that thought using 160* was too radical of a drop. I had found one potential application that used 170* t-stats, but when then 160's took off, I left the 170 option alone.

Fast forward to a couple of weeks ago, I acquired a spare Thermostat Housing at one of my local yards, and decided to revisit the 170 option. For me the reasoning is simple, when Dan (Daytrepper) did my 100k service in April, we were discussing some issues my car was having that were found by using Ross's DRBIII. We decided to go from the 160 to OEM 180. Now after several months, precious little has changed with my car, other than the transmission temperatures being much higher than I like them to be, especially with the high stall torque converter installed.

So, I revisited the 170 option. I acquired one from Advance Auto, and gave it the once over. I also took my spare t-stat housing with me. It is the correct size for the housing. So, I brought it home. Had to get out the Dremel to modify it slightly to fully fit the housing. I also decided to drill a hole in the t-stat to allow for some flow when the t-stat is closed. Here are some pics below:







BTW, that is the Stant box, and part number for this 170* t-stat.
I will be installing this next weekend, will keep you posted on developments.
 

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The Womanizer!
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I'm curious what you consider a high temperature in your transmission? Even running with a 195 degree thermostat, with the pressure from the radiator cap givng you an extra 2 degrees per psi, normal operating engine temp is really close to 225 degrees running a 50/50 mix of anti-freeze. A trans temp of 180-190 degrees is quite normal and within operating ranges for your fluids.
 

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I recall you saying you car ran better and got better MPG after running factory T-Stat?

180 Degrees is the Operating temp of the 42LE. Do you have a extra external cooler besides the factory one?

170 Degree Thermostat in a car designed to run 190 ish just sounds too cold with no yet proven gains.
 

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I hit **** with sticks!
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Indeed, what are your trans operating temps? That has little to do with engine operating temps.

Our discussion basically consisted of the engine not reaching its designed operating temp, resulting in poor fuel trims, O2 readings, etc...How do you know little has changed, have you had it scanned again?

Also, thats not how the thermostat fits in the housing...its backwards...just in case lol.
 

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Farticcus of Plenticcus
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Discussion Starter #5
I'm curious what you consider a high temperature in your transmission? Even running with a 195 degree thermostat, with the pressure from the radiator cap givng you an extra 2 degrees per psi, normal operating engine temp is really close to 225 degrees running a 50/50 mix of anti-freeze. A trans temp of 180-190 degrees is quite normal and within operating ranges for your fluids.
The trans runs between 150 - 195 depending on traffic, city v. highway, etc.
I know with the 160 installed, with the factory cooler, the trans temp rarely got above 150.Maybe it is within operating specs, but I wanna try this out to see if there is much of a difference.

I recall you saying you car ran better and got better MPG after running factory T-Stat?

180 Degrees is the Operating temp of the 42LE. Do you have a extra external cooler besides the factory one?

170 Degree Thermostat in a car designed to run 190 ish just sounds too cold with no yet proven gains.
My mileage right now in the city is ~ 16 mpg. Which is what I mainly drive. My theory is that with the 170 installed, it will be close enough to the 180 that nothing will be affected but perhaps the trans temperatures. It is untested, and unproven at this point, but I have been curious about this for years, testing it is no big deal IMO.

Indeed, what are your trans operating temps? That has little to do with engine operating temps.

Our discussion basically consisted of the engine not reaching its designed operating temp, resulting in poor fuel trims, O2 readings, etc...How do you know little has changed, have you had it scanned again?

Also, thats not how the thermostat fits in the housing...its backwards...just in case lol.
I have scanned it with my Alex Peper OBDII scanner. I am seeing between 8-11 degrees of timing advance @ idle. Pretty much the same thing Ross saw. The LTFT's and STFT's were off, but I need to rescan to verify.

Yeah, I looked at the t-stat again, and got it in the right way!!
 

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I still havent installed the 160 i bought from you yet
 

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Where is your temp probe at? Is it in line and if so which one?

If your worried about trans temp you should just install a Trans Cooler. I've had one for many years. I have it running through the radiator then the cooler and back to the trans. Installing a external cooler should be a top thing for any 42LE owner, if not any automatic trans onwer.
 

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Farticcus of Plenticcus
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Discussion Starter #8
Where is your temp probe at? Is it in line and if so which one?

If your worried about trans temp you should just install a Trans Cooler. I've had one for many years. I have it running through the radiator then the cooler and back to the trans. Installing a external cooler should be a top thing for any 42LE owner, if not any automatic trans onwer.
It is in the pan....
I have installed an upgraded external cooler on my car.
It is about 4x's the capacity of the stock external cooler.
 

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just a little cross referencing, my 3.2 at 195 degrees idling at 560-580rpm in gear has spark advance of 14-16 degrees. 127 degrees, in park, about 720rpm its 12-14.

dont want to jack the thread, but my car has been running a little warm, about 220 highway, and now its just a bit more than that and sitting on the 3rd line. is the stock 180 tstat the way to go?
 

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I hit **** with sticks!
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just a little cross referencing, my 3.2 at 195 degrees idling at 560-580rpm in gear has spark advance of 14-16 degrees. 127 degrees, in park, about 720rpm its 12-14.

dont want to jack the thread, but my car has been running a little warm, about 220 highway, and now its just a bit more than that and sitting on the 3rd line. is the stock 180 tstat the way to go?
Should be 0-4 degrees. You may have some timing issues.

Stock thermostat is the ticket. Keeps the engine at the temperature it was designed to run at.

Trans normal temp is 175-200, but the cooler the better.
 

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Farticcus of Plenticcus
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Discussion Starter #11
Should be 0-4 degrees. You may have some timing issues.

IMO, Stock thermostat is the ticket. Keeps the engine at the temperature it was designed to run at.

Trans normal temp is 175-200, but the cooler the better.
So I am in the normal range then...
I still think I am going to give it a try...
I mean, 10 degrees never killed anyone.
And if I can lower my trans temps by 10 degrees, then that is a win-win!!
 

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Should be 0-4 degrees. You may have some timing issues.

IMO, Stock thermostat is the ticket. Keeps the engine at the temperature it was designed to run at.

Trans normal temp is 175-200, but the cooler the better.
our 2.7 is the same way, both run great, good mileage. the lowest the 2.7 went was 5 before jumping back to 11
 

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I hit **** with sticks!
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our 2.7 is the same way, both run great, good mileage. the lowest the 2.7 went was 5 before jumping back to 11
2.7 is a different animal, not sure what the timing is supposed to be on those off the top of my head.

3.2/5 should be 0-4 degrees.
 

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The only way I can see any of this discussion even mattering is if the thermostat closes during normal running of the car. So tell me that the T-stat opens and closes a whole bunch and put my mind at ease. Otherwise Tom just really likes to drain and refill coolant.
 

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I hit **** with sticks!
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37,763 Posts
The only way I can see any of this discussion even mattering is if the thermostat closes during normal running of the car. So tell me that the T-stat opens and closes a whole bunch and put my mind at ease. Otherwise Tom just really likes to drain and refill coolant.
It does, thats how it regulates temperature. Engine cools when it opens, so it will close partially etc, then engine heats up, opens fully, etc....on and on and on...if the engine got cold enough, the t-stat would close, but its hard to say if it will, depends on what its doing.

I cant see any real effects of 10 degrees making it worth it to even mess with the thermostat, like I said, car, PCM and everything is designed to run at normal temperature with a normal t-stat.
 

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Farticcus of Plenticcus
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Discussion Starter #16
10 degree on the open road might be pretty significant.
Only way to find out....
 

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Might reduce duty cycle of the cooling fans, so fan motors might last longer. Since the fans are almost always cycling some, if the thermostat kept them from running as much, the engine temperature should still be regulated correctly. *IF* the fans are not cycling (due to overcooling in cooler weather and when the a.c. is not running), then maybe the engine temperature would be lower than it otherwise would be - something that would have to be looked at.
 

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i think im going to try this 170 t-stat, my 3.2 has the base radiator from a 2.7 after it got hit. ever since i put that radiator in it ran a little hotter. but more than likely its the garden hose water and cheap antifreeze i used.

dan, i had a thought concerning the timing. my 3.2 is running a 2.7 pcm... more spark advance on the 2.7 programming?
 

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I hit **** with sticks!
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37,763 Posts
i think im going to try this 170 t-stat, my 3.2 has the base radiator from a 2.7 after it got hit. ever since i put that radiator in it ran a little hotter. but more than likely its the garden hose water and cheap antifreeze i used.

dan, i had a thought concerning the timing. my 3.2 is running a 2.7 pcm... more spark advance on the 2.7 programming?
Nope, they will run right where they should on the 2.7 pcm. 0-4 degrees. Timing belt might be off a tooth or two. That could cause your hot running as well. Check your antifreeze mix, if its too much antifreeze, could cause a hot run in some circumstances. Doesnt really make a difference if you used tap water or not.
 

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we have a lot of rust here, im betting the rust is precipitating out of the water and plugging up the radiator. over the last 18 months its slowly gotten hotter.
 
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