If anybody is concerned that the Dorman thermostat is of lower quality, I am also fairly sure that both the stock GM/ACDelco and this Dorman thermostat are made by the same company/plant.
They both say
"made in Czech Republic" on the packaging, have similar numbers and scan codes etched onto the wax pellet body, and where the the GM part# sticker is on the side of the housing, you can see where this sticker has been peeled off of the Dorman, as evidenced by residual adhesive.

 

Not to challenge your claim but I looked at both thermostats on my 1.4 sonic. The Dorman had a different spring retainer, a different guide that slides in and out over the wax pellet housing. The retainer tabs that holds the spring assembly in place are better constructed. I wish I had a photo but I think I would need too take any. The problem is that my OEM was built up with the engine at time of production. Sometime in late 2014. Manufacturers make changes all the time for various reasons.

 

What a great thread, my 2013 40K miles has always smelled of antifreeze after I drive it--especially in the summer, I garage it and the smell is horrific in the garage every time I use it, I believe the odor is the water outlet which distorts just enough to allow some venting, although there is no leakage with the dealers static pressure test and hardly noticeable coolant loss I believe the temperature is too hot for the plastic parts long term, I'm sure the GM engineers have figured out why all the coolant related failures happen but are stuck in a rock and a hard place in that they have to satisfy the emissions with the high temps but experience high failure rates of the cooling systems, hey its all good for car sales with the reduced life on the engine from the heat----I'll be doing this mod soon !!!

 

I agree.
I think that the plastic cooling system components are very close to their limits of durability, especially longterm.
My 13 Sonic has had 4 water pumps (not plastic, but the seals are definitely stressed), 2 resivoirs, a water outlet, and a radiator replaced.
I think that lowering both the temperature and pressure will greatly reduce the stress on these parts.
Lower pressure surge tank caps are available, and are definitely recommended as well.
GM/ACDelco part#s are:
15 psi - 15075117 / RC98
9 psi. - 88986846 / RC108
The 9 psi cap is probably best used after the cooler thermostat, and an auxiliary radiator fan switch is installed.

 

Interesting.
Did you buy the Dorman 902-2080?
I just installed a second one in my wife's 2017 Trax tonight, and both of them are identical in construction to the originals.
I have seen the ones that have a different design to the machanical parts, so I presume those are the ones you are talking about.
Apparently those are made by
Motorad???

 

Dorman Products - 902-808

Integrated Thermostat Housing Assembly With Sensor

www.dormanproducts.com

This is the one listed for my Chevy Sonic.

 

902-808 is the correct one for stock replacement.
But we are talking about using the Dorman 902-2080, which is intended for the Volt/ELR, and swapping its internals into the original housing, to make a cooler operating thermostat for the turbo engines.
Now the OEM opening temperature for the Volt/ELR is the same as the Sonic/Cruze/Trax LUV 1.4, at 217°F.
Somehow, this 902-2080 is opening at 175-185°...
I can only presume that this thermostat was originally intended for for a market where emissions regulations are not as strict.

 

Just did a road trip with my wife's Trax with the new thermostat.
Ran between 170-180°F the whole time

 

I was wondering if you were able to read your fuel trims on a scanner when running the cooler temps and comparing them to the OEM thermostat?
That would give you an indication if your running the same rich/lean mixture at a lower temperature.

 

I'm able to get them, but I didnt bother looking at them beforehand.
I'll look to see what they are currently at tomorrow.
Fuel economy has been great though.
Just over 34 mpg (DIC) fully loaded, and with A/C running the whole time over 400 miles.
Mix of interstate, state highway, back country roads, and some in-town driving.

 

Ok just got home and fuel economy on the DIC indicates 34.6 mpg.
The long term fuel trims on the trip home floated around from -3.5% to
+3.5% most of the time, often under +/-1%.
On rare occasions, I would see momentary spikes to a little over +/-5%.
It seemed to spend a little more time in the negative territory than positive overall.

 

Ok just got home and fuel economy on the DIC indicates 34.6 mpg.
The long term fuel trims on the trip home floated around from -3.5% to
+3.5% most of the time, often under +/-1%.
On rare occasions, I would see momentary spikes to a little over +/-5%.
It seemed to spend a little more time in the negative territory than positive overall.

What do you think of these fuel trims ??
Still waiting on the 15psi cap, thermostat change looks simple, I did discover a possible cheaper thermostat:

Amazon.com: 89018168 for GM Thermostat 187° Engine Coolant Thermostat with Seal Kit: Automotive

Buy 89018168 for GM Thermostat 187° Engine Coolant Thermostat with Seal Kit: Thermostats - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

9 psi may be a bit low. I went with a 15 psi cap. For every psi reduction you lower the boiling point of the coolant 3 degrees. That's using a 50/50 mixture of coolant that is still serviceable.
Being at sea level it's not as critical than being at higher elevations. Even though your temperature is lowered by using a different thermostat you still build up pressure in the cooling system. You just don't want the coolant to come close to a boiling point that is lowered by a lower rated cap.

 

Agreed if you are still using a stock thermostat that 9 psi is a bit low.
But with the cooler thermostat and an auxiliary fan switch, 9 psi is quite acceptable.
True, it does give you less margin if the engine does run hot, but if you monitor your temperature, you should be able to spot a problem well before things get too hot.
Then again, it may also help prevent a component failure that could result in coolant loss, and subsequent overheating...

 

I think the fuel trims look pretty normal.
They will typically fluctuate a bit like that.
As for that thermostat you posted, you know that isnt a direct replacement, right?
You would have to modify it heavily to try getting to fit a stock housing.
Also, since these are inlet side thermostats, you will have around a 5-15°F temperature rise at the water oulet.
So a thermostat that starts to open at 187° on the inlet side will result in about 197° outlet temperatures, +/-5° depending on engine load.

 

Can't you just replace the fan sensor rather then wiring up a switch?

And I don't know why you'd want to use a lower psi cap. 20 isn't going to hurt it.

The gen2's run the lower thermostat and still have the 20.

 

There isnt a "fan sensor" or fan switch.
There are coolant temperature sensors which report to the PCM.
The PCM tnen decides when to activate the fan.
The PCM uses these coolant temp sensors for all of its coolant temperature related decisions, so replacing them with ones of a different value would wreak havoc on many different operating calculations.
The add-on fan switch is an easy way to sense radiator temperature and trigger the low speed fan relay well before the PCM would.
I havent studied the Cruze cooling fan circuit, but on the Sonic And Trax, there is a place you can tap into one of the factory fan relays to trigger low fan speed without the PCM being aware of it.
If the Cruze uses 5 relays to control the fan, then it is likely this can work for them as well.

And pressure is as big, or even bigger factor on the durability of the above mentioned cooling system parts than just temperature alone.
Both my Sonic and my wife's Trax now have the cooler thermostat, the added fan switch, and the 9 psi caps.

 

9 psi runs no different then 20 psi.

Gen2. 190* fan 210* 20psi
Gen1. 220* fan 230* 20psi

So why lower it?

It just means you've lowered your overflow threshold.

Boiling or not. And it probably won't. But you'll overflow sooner and easier.

Coolant doesn't have to boil to overflow.
It just gets hot enough to build pressure surpassing the cap.

 

I never claimed it ran different.
Just that there is less stress on above mentioned parts, and their lifespan will likely be much longer.
I am aware that the boil over threshold is lower, but I monitor temps closely and wont let it get too hot.
And like I also said, both our vehicles now run considerably cooler than stock...

 

Cooler then stock is all you need.

That colder 40* or whatever works wonders on parts lasting longer.

That stock temp for the gen1 is why you all have the problems you all have. I don't know what GM was thinking when they did that. It certainly didn't do wonders for their profits.

 

Cooler then stock is all you need.

That colder 40* or whatever works wonders on parts lasting longer.

That stock temp for the gen1 is why you all have the problems you all have. I don't know what GM was thinking when they did that. It certainly didn't do wonders for their profits.

Higher temps are for emissions. You get a cleaner burn at higher temps. That is why I believe the ECU is program to run at higher temps for cleaner emissions. If the temps run colder then the ECU may not reach its Optimum settings for proper emmisions. It may not make a difference to the daily driver but that is why the higher running temps. Too bad the failure rate of these parts is high from higher temps.

 

Agreed.
The lower temps play a major role.
The plastics are physically stronger at the lower temps.
But pressure is also important.
I've seen several sudden failures of surge tanks rupturing, even radiator header tanks suddenly give way, leading to total loss of system pressurization, rapid coolant loss, and naturally immediate overheating that leads to a tow bill.
When you see how thin some of these plastic parts are, it's a wonder they last as long as they do.
Pressure is no less than half the culprit...
If you arent comfortable with 9 psi, at least consider 15 psi...

 

NOX goes up.

 

Engine temperature wont significantly affect NOx.
Maybe if its overheating it might affect it more.
NOx forms when combustion temps exceed around 2500°F.
They used to control this with EGR.
The exhaust gas was mixed into the intake charge to act as a buffer gas, preventing peak combustion temps from crossing over 2500°.
Nowadays, they simply allow it to form during combustion, and use improved catalytic converters to break it back down.
The higher engine temps are meant to help reduce hydrocarbon emissions. The difference is small though. But with the EPA counting every molecule coming out of the tailpipe, it sometimes helps tip the scales into a more favorable emissions tier category, which gets additional credits to the manufacturer...

 

And some of the problems persist to this day, sometimes despite 2 or 3 supposed design revisions to address known issues...

This engine was an Opel design to begin with, so it was in use in Europe for 3-4 years before being offered in the U.S. market.
It had sufficient time to get the bugs ironed out.
I dont know what temps or pressures these early European market vehicles used though.
Perhaps GM upped them on the U.S. models.

 

Thermostat opening is 217 F(103 C), to hell with that, i was thinking of replacing the thermostat inside but the cadillac thermostat is almost 100$ here in romania. I'll try with buying the older gen thermostat from the 1.4 opel astra h/g and maybe i'll get lucky with that. I have already replaced my thermostat because it was leaking and when i wanted to only change the gasket the thermostat ears broke off so i had to buy a new one. My car (after it warms up) runs from 99 C up to 108 C but i would like something cooler aswell and i can't find any dorman's parts in romania or in europe. Usually it sits between 103 to 108 C. How i found out? Easy, for opel there is a 2nd menu in the CB cluster area wich shows the temp cool, alternator charge and a few more things. It should work on the cruze aswell but i believe you will need a TECH2 to activate them.
LE: i finally found the right thermostat for chevy volt-cadillac-opel ampera;
CALORSTAT by Vernet 32$ https://www.autodoc24.ro/calorstat-by-vernet/12209136

 

Just an update.
My Sonic has been using the Dorman 176° thermostat for over a month now, and our Trax has had it for over 2 weeks, and both passed OBD inspection today.
The spring issue I mentioned above doesnt seem to have made a difference after all, as both vehicles seem to have pretty much the same operating temps on the highway.
Both cars are daily driven, and
no codes have appeared on either vehicle.

 

IIRC.

You only need somewhere around 135 before emissions ready. Might be lower. Been a long time since I checked it out.

 

I assume you are talking about going to closed loop.
And 133-135°F used to be the minimum temp before closed loop was permitted on older GM models, but these cars are capable of going to closed loop operation at much lower temps.
I've seen my Sonic go to closed loop after a cold start at ~45°F ambient at ~65°F coolant temperature in as little as around 40 seconds after starting.

But if you are talking about the readiness monitors, they are already set from previous drives, regardless of current coolant temps.

 

Just wanted to say thank you for the solution you provided and taking the time to share it with the rest of us. I have a 2012 1.4 that has had all the problems; several multiple times. I read your solution, ordered the Dorman thermostat, and received it today. I removed my old thermostat housing, removed the thermostat, then realized i had replaced it with a non-oem the last time it failed. You must have the oem housing for this to work!
Fully committed, i went to the dealer and bought the oem part, which i brought home, modified with the "old school" thermostat, and reinstalled. It works exactly as you said. I've been driving around all afternoon, watching the almost imperceptible movement of the guage as the thermostat opens and closes. Perfect!
I also replaced the cap with a 15psi cap. Thanks again.

 

Just wanted to say thank you for the solution you provided and taking the time to share it with the rest of us. I have a 2012 1.4 that has had all the problems; several multiple times. I read your solution, ordered the Dorman thermostat, and received it today. I removed my old thermostat housing, removed the thermostat, then realized i had replaced it with a non-oem the last time it failed. You must have the oem housing for this to work!
Fully committed, i went to the dealer and bought the oem part, which i brought home, modified with the "old school" thermostat, and reinstalled. It works exactly as you said. I've been driving around all afternoon, watching the almost imperceptible movement of the guage as the thermostat opens and closes. Perfect!
I also replaced the cap with a 15psi cap. Thanks again.

Did you replace the reservoir too or just the cap?

 

I have an actual temperature gauge on my '66 chevelle that reads in fahrenheit. Thermostat opens at 195*F and I can see the temp gauge drop when it does. Now that's the way it should be without computer controlled or assisted crap. Ahhh the good ole days gone by....