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2002 chevy trailblazer_lt
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Discussion Starter · #1 ·
So im looking into replacing my thermostat, i beleive the OEM peice to be a 195* unit, im looking to buy an aftermarket 180* unit, i was thinking about a 160* but thats overkill so im looking for a place that sells 180* units for our trucks? ive searched all over the place and havent found anywere yet, anyone know where they sell a 180* replacement for our 4.2s?
 

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Discussion Starter · #3 ·
im looking to get a 180*, no tune is required for a lower temp thermostat all it does it dumps more coolant out of the radiator when it excedes that temp, the only thing a tune would do is change the fan turn on points to correspond with the lower desired temperature but its not needed whatsoever
 

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2005 chevy trailblazer_ls_ext
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im looking to get a 180*, no tune is required for a lower temp thermostat all it does it dumps more coolant out of the radiator when it excedes that temp, the only thing a tune would do is change the fan turn on points to correspond with the lower desired temperature but its not needed whatsoever
Most of us end up replacing our thermostat because the engine is running too cold. On my 05 the temp. gauge was dropping about 2 lines below 210. Believe me, it made it VERY gutless. It had far less power than normal and it was using quite a lot more gas.

I've never seen anyone sell a 180 degree thermostat for this engine.
I take that back - there was someone about a year or more ago on here that found some place - not sure if it was a racing place or what that supposedly did make the lower temp thermostat. Might try using the search function.

BTW, just curious - do you have emissions inspections where you live?

Here is some interesting reading:

http://forums.trailvoy.com/search.php?searchid=2194720

I may have been wrong. After reading through a few of the posts, the 160 and 180 thermostats may have been for the SS V8 engines.
 

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2003 chevy trailblazer_ls
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im looking to get a 180*, no tune is required for a lower temp thermostat all it does it dumps more coolant out of the radiator when it excedes that temp, the only thing a tune would do is change the fan turn on points to correspond with the lower desired temperature but its not needed whatsoever
Odds are that a 180 t-stat will set a CEL. Mine was 2 clicks below center and it did set a code, mpg was down as well. Why do you want to go to a 180 t-stat? These engines are designed to run at a higher temp.
 

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2005 chevy trailblazer_ls
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Cooler engine equals more hp

The cooler the engine the more hp you get. I haven't seen one for our platform but auto makers that have a racing division usually offer them for most of their cars i know Nismo makes them for Nissans they wouldn't be made unless they helped especially from the car dealer. That is why people usually go overkill when they get aftermarket fans.

If you are looking for something temporary like for racing i would look into the CryO2 system they make a kit for the intake and the radiator. It lowers the IAT by like 20 degrees on a warm day and would lower the engine more i would believe. Plus you can get a purge kit which is also awesome.
 

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2003 chevy trailblazer_lt
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180 thermostat

My buddy changed out his oem for a after market thermo 180 and whoever said it was gutless is right on the money he noticed a major HP and torque drop why who knows I know in the morning when i leave for work (5am) military..my TB (red) wants to take off cause the temp isnt all the way up(200ish) however I think changing the temp that much apperently does make the TB lag..if you live in the northern part of the states i would really think twice before purchasing one especially during the winter..I'm still doing some read up work on it...there's my 2 cents:tiphat
 

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my thermostat is bad i live in florida so i havent changed it yet but it runs the same at 180 no worse no better....city my tb runs 200 highway 180...
 

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Basic Vendor- Skid Plates
2007 chevy trailblazer_ls
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Heatsoak = Bad
Running an engine made of 2 dissimilar metals at a cooler temperature at which it's not designed to run = badddder than heat soak

Aluminum expands more than steel vs. temperature. Material properties (this is not "engineer" stuff... this is high school physics) say that when a piece of metal expands, even if it has a hole in it, the hole expands at the same rate and direction as if it had material there... i.e. the hole gets bigger as the metal expands... These engines have an aluminum block, aluminum pistons, steel crank, steel cams, and steel cylinder liners...

Assuming everything is designed to run at >195F, if you go colder than that, the aluminum will shrink more than the steel... This means that your pistons will "wiggle" more in the cylinders (and the skirts will scrape the cylinder walls more), and all of your hydrodynamic bearings (oil bearings, like the crank and cams) will be smaller, so not as much oil can get to them (not to mention the oil being slightly thicker, which makes it worse)...

In short, there is a reason that ~99% of your engine wear takes place during warm-up...

Now, having said that... in theory, the way an engine makes the most power is by having the hottest flame surrounded by the coldest engine... This is the sole principal of the Sterling Engine, and why it works...

In real life, though, the engine is designed to work at a certain temperature, and if it is not somewhere around that temperature, it isn't happy... In real life, the combustion chamber has to be hot enough to atomize the fuel into the air, and the bearings and pistons have to be at the right tolerances. This engine was designed to run between 195 and 240F, so that is where it will work best.

Mike
 

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2002 chevy trailblazer_ls
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:iagree:Our engines need to be at a certain temp to run their best. Where as most engines run better cooler, ones with dissimilar metals need to be a little hotter due to different expansion rates.


Please keep this thread on topic guys. I don't want a repeat of the last one. I will not hesitate to close this if the bickering starts over a difference of opinion again. If you have nothing nice to say, just don't post.
 

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2007 chevy trailblazer_ls
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:iagree:Our engines need to be at a certain temp to run their best. Where as most engines run better cooler, ones with dissimilar metals need to be a little hotter due to different expansion rates.
Yes, mostly... While this is true of most factory engines, you can build an engine to run slightly cooler, but you have to build the tolerances in to run at whatever temperature you plan on running it... Most factory engines, yes, they're made to run hot, because that's where they get better mileage and make better emissions...

Mike
 

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2003
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Yes, mostly... While this is true of most factory engines, you can build an engine to run slightly cooler, but you have to build the tolerances in to run at whatever temperature you plan on running it... Most factory engines, yes, they're made to run hot, because that's where they get better mileage and make better emissions...

Mike
Ah it's good to see the smart people chime in on these rare and wonderful engines like ours. It may be able to develop more horespower indeed if the PCM was tuned to accept the lower temperature parameters and they made sense to the rest of the computer tables and whatnot (highly technical term)

All I know is that when I was running slightly undertemp due to the open thermostat the PCM thought the engine was cold and it caused a rich condition. That was OK with the O2 sensors because the PCM was thinking the truck was cold and my mileage went for a chit and it ran like a dog without throwing a code.

Then it finally threw the overcooling code ..... replaced the thermostat and I regained the mileage and performance.
 

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2003 gmc envoy_sle
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Thermostat/Coolant Sensor replacement

I just wanted to say thanks for all the great info and pictures on here. Last weekend I replaced the thermostat and coolant sensor on my 2003 GMC Envoy. I of course have a Haynes manual, but the pictures leave a bit to be desired. The ones are here are AWESOME and go step by step to replace these items. I did both since my truck was throwing at 0128 code. I decided if I have to go to that much work, I might as well do both of them and save myself the trouble. I replaced my water pump in March of 2009 and wish I had discovered this site back then. WHAT A PAIN THAT WAS!!

I supposed I should mention that I'm a GIRL! I had an old 71 Firebird that I worked on for years, so I'm not afraid to get a little dirty. Working on the Envoy is not nearly as easy though.

This site has so much great info. I'm glad I found it.

Thanks so much. I'm sure next time the truck gives me another check engine light, I'll be searching for answers again.

:)
 

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Because the subject of PCM and engine temperature has come up in this thread, let me give a brief explanation of some of the variables involved. Unlike older engines, managed mechanically, or with rudimentary computer controls, changing ANY variable on our engine can throw off the entire system of checks and balances programmed into the computer.

For instance, lowering the overall temperature, as in changing or opening a thermostat, makes the air/fuel ratio and air density that controls that ratio change. Those changes mean that the engine must compensate and it does that by changing spark timing, fuel enrichment, and cam timing. Any of those changes cannot increase performance (unless you just plain get lucky) as the engine can vary all over the map as far as following the built in data tables that tell it what to do when, and under which circumstances. This is especially true for pre-06 models that use the MAP (manifold absolute pressure) version of the PCM versus the MAF (mass air flow). All the pre-06 PCM settings are calculated based on several assumptions, and changing those assumptions without a PCM data table change will toss the entire tune out the window. All of the above can effect the "drive-by-wire" setup as well.

Our engines are actually two things simultaneously: A tuning nightmare and a tuning marvel. The marvel is that the system has been well-balanced, and that it performs admirably. Fudging a bit on the factory safety factors in the tune (the factory has to tune an engine that will run as well in Alaska as it does in Dubai) can increase performance somewhat, and given the right parameters, a performance tune could be even more effective, but it takes a LOT of time and dyno work, plus reliability and drivability studies to know that a hot tune will actually work out well in real street driving scenarios. For the track, things are different, just make it as fast as possible in WOT exercises, but when the truck has to idle in hot traffic, run at freeway speeds for extended times, pull a trailer, etc., and do it all without a hick-up, it is a tough tune to find.
 

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Where are those Pics.

I need to do a thermostat and an 02 sensor. One member mentioned the pics that were posted last week, well that would be about a year ago now. Where can I find those? I may want to do the waterpump as well. Any input will be really appreciated!

Thanks,

Justin
 
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