is it okay to replace a 190 degree thermostat with a 170 degree thermostat?

On the computer controlled cars it's really not a good idea. The vehicle needs a minimum temp of 195° to run properly. On the OBD II cars running a 170° t stat could actually set a code.

The thing about t stats that some people get backwards is, all it controls is the minimum running tempature not the maximum. If you have a problem with your car running hot, a cooler t stat won't fix that problem. a 195° t stat will close if the coolant temp while running, drops below 195°, once past that it opens back up & coolant flow thru the rad again. So a 170° t stat would let the temp get all the way down to 170° before it closed & restricted coolant flow. Even non-computer controlled cars, thats too cool. Sludge cool build, MPG could go down. On a warm day, its really a non issuse (unless of course it sticks & thats a whole different story) because wheither you have a 195 or 170, the coolant problably isn't going to get close to minimum tempatures for the stat to close.

So where I'm at during the summer, once my stat opens....it's open for the rest of the day


(This post was edited by Sidom on Jun 23, 2009, 7:15 PM)

I totally agree with Sidom.
If your in a state that has emissions inspections, that lower thermostat can cause you to fail because the computer will remain in open loop status.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Agree, agree! Lowering rating of a thermostat is a bad idea. Whether a 160 or 195F they are both open the same at the 195 which is NOT too much for an engine. There were engineered engines to run at 160 (never heard of 170 posted?) but only saw that for marine use - no computer controls and engines under stresses a car would never see,

T
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Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

I had a problem with the thermostat, it was stuck closed.
I went to pepboys and they had 2 available, 170 and 180... book said it should be 190
installed the 170 t stat few days before posting this thread (woops), guy behind the counter seemed to think it was a great idea.. ehh
well, live in Florida, damn thing gets way hot sometimes ya know.

It was a real pain in the ass because i was removing the wrong pieces and somehow pulled out the gasket on the metal part that connects to the upper hose, couldn't get the damn thing back in so i just tightened up without the gasket... hasn't leaked so far. then i found the t stat housing underneath all these wires that connected to the LOWER hose.

the book really left a lot out in the steps and made it seem like the UPPER house was where the housing should be. beginning to hate this book.
is there a better manual than haynes for an 03 eclipse 3.0L?
also how serious could 20 degrees be? should i change that ASAP? pepboys didn't even have a 190

Change it to correct one ASAP. Open t-stat is open whether a cooler rated one or not. It does nothing but confuse the car to alter that. If running too hot then there's a problem to fix,

T
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Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

i have to agree as well with the rest of you all
running a cooler thermostat really not the way to go
on a cumputer controlled car because not only will
the onboard computer be fooled into thinking that
the engine needs more fuel because it thinks its still

at a warm up cycle and you could have a slight increase
in rpms as well because again it thinks it needs more
fuel but you could also create other problems like oil sludging
related from a too cooller running engine so definatly
stay with oem settings

Quote

No, that's not true at all. The computer won't be fooled because the coolant temp sensor is still reporting accurately and the computer will respond correctly for the actual temp of the engine. The problem is that the computer requires a minimum temp before it switches to closed loop so it continues to ignore some of the sensors and the cooler engine won't burn the fuel properly.




78 Corvette Pace Car For Sale-18k mi orig-Florida

In short - use the temp rating that was OE in cars. Few if any benefit from lowering a t-stats opening temp. If vehicle is or has an overheating problem that's a separate issue............and lowering t-stats wide open range won't change or fix that!

T
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Tom Greenleaf - MetroWest, Boston
http://acsource.net/acforum/index.php

All the guys are correct here. Only thing I have to offer is, Nearly all of the manuals other than Haynes are better. Motors, Mitchell, Chilton (my least favorite next to Haynes). Your public library is usually a good source as well.
Loren
SW Washington

Thanks for the tip.
I was able to locate a Factory Service Manual for 3g Eclipse and Eclipse Spyder.
All in all some 3 or 4 thousand pages.

Best part is all PDF Document and free download :)

Ain't the internet great?
Loren
SW Washington

The thermostat's main purpose is to reduce engine wear. Most engine wear happens during start and warm up. If you install a lower temp thermostat (or remove the thermostat alltogether) you increase warm up time and reduce engine life.

Haynes Manuals are so generic...... throw them away and don't buy another.
"It's some kind of a Crow's Foot." LOL

(This post was edited by GlennAB1 on Aug 26, 2009, 6:23 PM)

Just to keep things straight.... The main purpose of a T stat is to maintain a minium engine operating tempature. Some of the points you make are valid but a T stat is going to have no affect what soever on a cold soak start....

I agree with you on Haynes...........

In Reply To

On a cold soak start...... there's really nothing we can do to reduce wear then, except run the best oil (like AMSOIL), run at low RPM/don't drive till temp is off the peg.

Quickly reaching and maintianing minimum engine operating temperature is for what reason?
"It's some kind of a Crow's Foot." LOL

(This post was edited by GlennAB1 on Aug 26, 2009, 6:58 PM)

In Reply To

Whole slew of reasons Glenn, from drivability, fuel economy, emissions, owner comfort and yes you can throw engine wear in there as ONE of the many reasons that the main purpose of a thermostat is to maintain minium operating tempature of an engine.

In Reply To

Being a mechanic, I have to place engine wear at the top of the list....... Owner comfort: yeah, I like it to warm up fast in the Winter. Emissions: Not concerned about that with my '66. Fuel Economy: Sure we want it to warm up fast so the idle kicks down, but if we're driving it right away there's not much fuel economy difference. Drivability...... hmmmm, got me there.
"It's some kind of a Crow's Foot." LOL

Quote

That is pure nonsense

The engine needs to maintain a minimum temp for complete combustion and complete vaporization of the fuel mixture. If you run an engine too cold, you can do serious long term damages and running a car without a thermostat causes the engine to lose all control of temperature and should never be done




78 Corvette Pace Car For Sale-18k mi orig-Florida

In Reply To

Your response doesn't make any sense...... Maybe you didn't comprehend what I wrote?
"It's some kind of a Crow's Foot." LOL

In Reply To

You know we're really not accomplishing anything here anymore Glenn... HT's response is crystal clear and makes perfect sense.....

This is auto shop 101 and if you wanna go thru life believing the main purpose in a T stats life is to reduce engine wear, you go with it bro...... and when your get this as the million dollar question, you stick to guns & giv'em your answer........just hope I'm watching...

Time to end this one.....we're just wasting bandwidth now.......

I was merely pointing out a fact (engine 101) that you guys hadn't mentioned.
Anyone can GOOGLE: thermostat and engine wear and see if I'm full of sh!t.
Sorry!
"It's some kind of a Crow's Foot." LOL

We don't need Google for that..........




78 Corvette Pace Car For Sale-18k mi orig-Florida

>>We don't need Google for that.......... << HT is right. We don't need Google for that. You made that obvious. You may know about airplanes, but.... I know nothing about jet engines, so, I don't profess to know... Just a hint. I do know about internal combustion engines, though.
Loren
SW Washington

In Reply To

I was done with this.....

Initially, the thermostat is there so the engine heats up to it operating temperature as quickly as possible, in order to reduce engine wear. If there weren't a thermostat the engine would wear out quickly and there wouldn't be any concern about "fuel economy, emissions, and owner comfort," which, yes the thermostat is also there for.

Yes, I'm educated in gas turbine (jet) engines, but also gas piston engines...... both being internal combustion engines.
"It's some kind of a Crow's Foot." LOL

(This post was edited by GlennAB1 on Sep 1, 2009, 4:41 PM)

No, thermostats were'nt invented for creature comfort. They were designed just for what they are...to keep engine temps even. Initially, for fuel vaporization. Many engines had thermostats before heaters were introduced.
Loren
SW Washington