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The oil temperature is not really related to the coolant temperature and usually runs hotter than the coolant. If this wasn't the case why do performance cars run separate oil coolers? A friend had an original mini minor and fitted a gauge that had a switch that went from the coolant to oil temperature at the flick of a switch, so the same gauge was used for both. Coolant ran at 170F when cruising and the oil ran at 250F when cruising. I know the transmission was in the sump, but it was also ribbed alloy to help with cooling.
 

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OK, let’s start!
I had multiple Cruze cars since 2011, unfortunately I can’t say I have/had one free of issues! Talking about the heating and cooling, I saw different & multiple issues reported by people. I did many changes to my cars during the years and I’m going to share with you a few interesting things about the thermostat, specific for 1.4L turbo (ECO). It can be similar issues for other trims, even for Diesel, but the cars I tested & modified are Cruze ECO 2011-2012.
Based on testing 4 cars, here are my observations:
First, the “input data”:

  1. The OE Thermostat on Chevy Cruze ECO (1.4L turbo) from 2011 to 2016, is with a wax thermostatic element that starts opening at 105°C (221°F).
  2. The OE Thermostat is also wired and controlled by ECM. Based on different algorithms and program codes, the thermostat can open at any temperature at any time, if the ECM requires that!
  3. The water temperature display gauge is… a joke! I monitored it for different cars and compared with data from OBD. The dial moves when the temperatures increases until… until 185°F (85°C) only! Then stays there, right before 6 o’clock, no matter how high is the real water temperature. When I tested this, I changed the coolant concentration, adding much more water into the system and let the engine run until the water started boiling. The gauge was at the same position max position, telling me “everything’s ok!
View attachment 254945

4. The expansion OE tank cap is opening only at 20PSI.

Under all these conditions, the coolant temperatures during normal driving conditions stays around 220°-230°F. I said normal driving conditions because when the engine is overheating, the ECM controls and changes everything. It may open the shutter grille to help cooling down and also it can open the thermostat at any temperatures it “wants”, based on data collection. So, not only that you drive with coolant at high temperature, but also the entire system is at high pressure, since the tank cap opens over 20 PSI. In theory, a higher engine operating temperature helps improving its performances. Well, maintaining a higher temperature for the engine and cooling system requires also better quality system parts. Coolant’s boiling point is way too high under the condition I mentioned so everything is ok until… One small crack into the system will lower the PSI and of course the boiling point of your coolant. Add adding more water into the system and you will lower it even more until the coolant will start boiling time to time, without you notice it I replaced the recovery tank a few times, and many hoses all the time! Many others did the same things on this forum.
Sick of changing parts all year along I decided to change the thermostat and go “old school”. It took me a while until I found something that works but here is what I did. I bought a new thermostat housing 55593035Dorman 902-2080 (GM) that is for Cadillac ELR 2014 Chevy Volt 2011-2014. Do not buy MotoRad, it is a different new model, it will not work! You need the one with the “cage”, see the attachment. The housing is different from the outside, but the internal thermostat is fully compatible with Cruze’s thermostat housing. Push the cage and rotate as in my picture, then take out the spring and “cage”. The thermostat will come out relatively easy. It looks the same as the other one, only the wax inside is different and starts opening at 176°F (80°C). Be careful with the 2 legs, don’t bend them so they can go straight back into the housing.
I’ll not got into details of how to take out the existing thermostat, there are good posts on this forum. Put everything back, and make sure you have enough coolant. Then, old school again, I changed the tank cover with one that is opening at 15 PSI, not 20 PSI (MOTORAD T46 )!
I did this replacement on 6 ECO-s and these cars have between 500 to 3200 miles since. No issues at all! The temperature goes usually up to ~184°F then the thermostat is fully opened so the temperature goes down around 180°F. I didn’t notice any drastic changes to MPG! I have hot air blowing inside the car as I had before the swap.
I did all the changes I mentioned because me and my friends have multiple issues with the cooling system since 2011. If you like the solution and have questions, please let me know. I don’t want to argue with anybody about why GM built the system in the way it is so don’t challenge me! :p

View attachment 254953 View attachment 254961 View attachment 254969
First of all, thank you for this post. I have been racking my brain trying to figure out what to do about finding a thermostat with a lower temperature setting for opening. I have 2014 1.4L Eco with turbo. Will the thermostat tou mentioned work on this model as well? Again, thank you!
 

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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?
 

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Discussion Starter · #125 ·
First of all, thank you for this post. I have been racking my brain trying to figure out what to do about finding a thermostat with a lower temperature setting for opening. I have 2014 1.4L Eco with turbo. Will the thermostat tou mentioned work on this model as well? Again, thank you!
All 1.4l turbo Gen1.
 

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I think you should have spent more time identifying the root cause of your other problems. In my ownership of the Cruze I haven't had to replace those components and haven't had to top off any antifreeze.

I don't think what you did was a good idea. The engine needs to run hot enough for efficiency and without a re-tune, you might see a drop in fuel economy. Furthermore, engine oil needs to operate above the boiling point of water to prevent condensation and water contamination from building up. That point is 212F. You running the thermostat below that temperature means you'll likely also need to change oil more often since oil will not reach above the boiling point of water, which may cause it to break down more quickly.

A 195F thermostat may have been more appropriate.
I agree. A better way to address the issue would have been to use a higher percentage of coolant to water. The heat transfer would be better. Nothing major, but I run a ratio of approximately 60/40 coolant to water. If we're getting precise, I lower the freezing point of the DexCool to about -40. Its normal at 50/50 tends to vary between -27 and -32.
 

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I agree. A better way to address the issue would have been to use a higher percentage of coolant to water. The heat transfer would be better. Nothing major, but I run a ratio of approximately 60/40 coolant to water. If we're getting precise, I lower the freezing point of the DexCool to about -40. Its normal at 50/50 tends to vary between -27 and -32.
Increasing the amount of ethylene glycol solution(antifreeze/coolant) in the cooling system does NOT increase heat transfer. There is no common safe liquid with a specific heat higher than water. Anything conventional you add to water reduces it's capacity to absorb heat. As long as you aren't boiling the water and creating air bubbles, straight water is actually the best coolant. There's a reason race vehicles(even ones not banned from using EG coolants because of how they coat racing surfaces during cooling system failures.) Use straight water and possibly a minimal lubricant/corrosion resistance package as coolant. Water is most efficient, remotely common, safe and inexpensive coolant.
 

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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:
Did you confirm that that the 187°F thermostat only would work? Direct replacement for the Cruze thermostat, or did you have to swap the guts like Cruise Cruze?
 

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Discussion Starter · #129 ·
KENSTV123 is wrong with the thermostat, at least for Gen1. The model needs to have the pins to connect to he wires also, this one is just a thermostat that won't work for Gen1 (1.4l).
Xtrem: in theory yes, you need to find the root cause but in my opinion the quality of components is not the best and you will not be able to keep the high pressure into the system so the coolant will get air and boil. And you are wrong about running the engine at lower temperature, I work withe engines but I won't start arguing, it is a long theory and we will talk forever. I did it for over 20 cars and had only one minor issues in one situation. It works grate in cold (very cold) weather or high temperatures as we had this summer.
To summarize it: who wants to do it can ask me for support but if you want to argue I'll not get involved. :)
 

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Yeah, I realized after I wrote the question that it wouldn't be a full swap, but I was hoping that it would be a candidate for a change of just the guts. $6 is a lot cheaper than $50. It won't be the first thing I work on anyways. I gotta fix a leak on the turbo coolant hose first. I'm trying the cheap "cut the hose crimp off and replace the hose with hose clamps" because removing the turbo isn't on my list of things to do.
 

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OK, let’s start!
I had multiple Cruze cars since 2011, unfortunately I can’t say I have/had one free of issues! Talking about the heating and cooling, I saw different & multiple issues reported by people. I did many changes to my cars during the years and I’m going to share with you a few interesting things about the thermostat, specific for 1.4L turbo (ECO). It can be similar issues for other trims, even for Diesel, but the cars I tested & modified are Cruze ECO 2011-2012.
Based on testing 4 cars, here are my observations:
First, the “input data”:

  1. The OE Thermostat on Chevy Cruze ECO (1.4L turbo) from 2011 to 2016, is with a wax thermostatic element that starts opening at 105°C (221°F).
  2. The OE Thermostat is also wired and controlled by ECM. Based on different algorithms and program codes, the thermostat can open at any temperature at any time, if the ECM requires that!
  3. The water temperature display gauge is… a joke! I monitored it for different cars and compared with data from OBD. The dial moves when the temperatures increases until… until 185°F (85°C) only! Then stays there, right before 6 o’clock, no matter how high is the real water temperature. When I tested this, I changed the coolant concentration, adding much more water into the system and let the engine run until the water started boiling. The gauge was at the same position max position, telling me “everything’s ok!
View attachment 254945

4. The expansion OE tank cap is opening only at 20PSI.

Under all these conditions, the coolant temperatures during normal driving conditions stays around 220°-230°F. I said normal driving conditions because when the engine is overheating, the ECM controls and changes everything. It may open the shutter grille to help cooling down and also it can open the thermostat at any temperatures it “wants”, based on data collection. So, not only that you drive with coolant at high temperature, but also the entire system is at high pressure, since the tank cap opens over 20 PSI. In theory, a higher engine operating temperature helps improving its performances. Well, maintaining a higher temperature for the engine and cooling system requires also better quality system parts. Coolant’s boiling point is way too high under the condition I mentioned so everything is ok until… One small crack into the system will lower the PSI and of course the boiling point of your coolant. Add adding more water into the system and you will lower it even more until the coolant will start boiling time to time, without you notice it I replaced the recovery tank a few times, and many hoses all the time! Many others did the same things on this forum.
Sick of changing parts all year along I decided to change the thermostat and go “old school”. It took me a while until I found something that works but here is what I did. I bought a new thermostat housing 55593035Dorman 902-2080 (GM) that is for Cadillac ELR 2014 Chevy Volt 2011-2014. Do not buy MotoRad, it is a different new model, it will not work! You need the one with the “cage”, see the attachment. The housing is different from the outside, but the internal thermostat is fully compatible with Cruze’s thermostat housing. Push the cage and rotate as in my picture, then take out the spring and “cage”. The thermostat will come out relatively easy. It looks the same as the other one, only the wax inside is different and starts opening at 176°F (80°C). Be careful with the 2 legs, don’t bend them so they can go straight back into the housing.
I’ll not got into details of how to take out the existing thermostat, there are good posts on this forum. Put everything back, and make sure you have enough coolant. Then, old school again, I changed the tank cover with one that is opening at 15 PSI, not 20 PSI (MOTORAD T46 )!
I did this replacement on 6 ECO-s and these cars have between 500 to 3200 miles since. No issues at all! The temperature goes usually up to ~184°F then the thermostat is fully opened so the temperature goes down around 180°F. I didn’t notice any drastic changes to MPG! I have hot air blowing inside the car as I had before the swap.
I did all the changes I mentioned because me and my friends have multiple issues with the cooling system since 2011. If you like the solution and have questions, please let me know. I don’t want to argue with anybody about why GM built the system in the way it is so don’t challenge me! :p

View attachment 254953 View attachment 254961 View attachment 254969
I drilled a 3/16 hole through mine temp stays around 200° +\- 5 you could drill two
 

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today, after procrastinating, I changed over to the lower temp thermostat, and replaced the leaking reservoir with 15 psi cap, and replaced bypass hose that was cracking and the reservoir hose. All parts either leaking or about to leak. milage is 105663. The changeover took about 2 hours, the hardest was removing the small hose from the thermostat....get the right tool, my plyers we’re difficult.
I immediately noticed my temp gauge...it actually fluctuates, looking like all works well.
I will give mpg and overall satisfaction soon
 

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Discussion Starter · #134 ·
r procrastinating, I changed over to the lower temp thermostat, and replaced the leaking reservoir with 15 psi cap, and replaced bypass hose
You will not have any issues just make sure you bleed the air properly from the bleeder valve!
MPG honestly I didn't see any difference, I still got 45MPG average last year for a trip from Detroit to Montreal.
 

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You will not have any issues just make sure you bleed the air properly from the bleeder valve!
MPG honestly I didn't see any difference, I still got 45MPG average last year for a trip from Detroit to Montreal.
took it for test today...62 mph with 44.9 gph air temp 82 ran for twenty minutes consistent readings..temp looks like two notch short of half way on temp gauge
288238
 

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You will not have any issues just make sure you bleed the air properly from the bleeder valve!
MPG honestly I didn't see any difference, I still got 45MPG average last year for a trip from Detroit to Montreal.
took it for test today...62 mph with 44.9 gph air temp 82 ran for twenty minutes consistent readings..temp looks like two notch short of half way on temp gauge
took it for test today...62 mph with 44.9 gph air temp 82 ran for twenty minutes consistent readings..temp looks like two notch short of half way on temp gauge
View attachment 288238
288239
288240
 

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Discussion Starter · #137 ·
Good job there! If you checked my post in detail you will see that the gauge will never go over half way, even if you will boil the coolant! At least for Gen1! :)
 

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Torque doesn't have the correct pid for oil temp.. you have to google and fix that. Mine never gets hotter.

It's impossible.

I've never seen it. In any vehicle or semi.
Drove a 2020 RAM rental pickup 2000 miles over the past couple of weeks. Oil temp consistently ran hotter than coolant. Coolant ranged from 206F to 220F while the oil ran 220F to 230F. Just sayin' - it's not impossible...
 
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