Hi guys, question regarding my coolant temps lately. I just had a new GM ecotec thermostat installed on July 21st of 2017 & it's worked fine with my temps reading around 171-180 when it's warmed up. In Ohio the last couple of weeks we have had sub zero temps ranging from 15% to ten below 0. My car stays in my attached insulated garage. I let me car warm up in the morning b 4 work. Today it hit 200 & the fans kicked on as they should & it dropped back down to 180 as it should however once I hit the freeway I noticed that my temps kept dropping until they got around 136 & then they stayed there for the rest of my drive. I drive 45 min one way for work each day & it's all freeway. Tonight on my way home it was even colder around 10% out & this time when I got on the freeway it dropped down to around 122%! When I got off the freeway & was driving in town my coolant temps climbed back up to around 160% & then when I pulled into my garage & let it idle for a min they climbed back up to 170 where they should be when my car is warm.

This all started a couple of weeks ago when this super cold weather started.

Do you guys think I'm having a thermostat sticking issue ? Again my thermostat is darn near bran new but I thought maybe the cold temps could be making it stick?

I thought maybe it was a sensor issue with a bad reading however when the temps fall the hot air that was once blowing out isn't as hot anymore so that tells me that the temp reading is correct.

Is it possible that it's just so darn cold that when I get out on the freeway @ 75mph with that 10% air coming in that my engine is just struggling that much to stay at normal operating temps ?

 

It's just cold.

It's been -40C(equal to -40F) here for the last two weeks and my temp won't reach regular temp while moving.

Drops 8C coasting towards a light. Barely blows heat.

You could always trying covering half the rad with cardboard. Probably something I should do.

 

Thanks clue that's what I was hoping it was from. Of course my coolant temps really drop when I turn my heater on but that's to be expected

 

even when its 0* here in Michigan, my car runs 180 all day once its fully warm. I had to replace my thermostat recently because my car was doing what you are describing. It really sucks to have no heat in the winter.

 

Sounds like its stuck open.

 

I've put two thermostats in this car in the 8 months I've had it. Haven't tried a GM one.

my car takes 15-20 miles before it even hits 170. it still blows hot air.

 

I just used a carquest one. $20

 

Yeah I put in one I got on Amazon.

 

I just can't see how it could be my thermostat. My OEM one that came with my car lasted around 7 years b 4 it stuck open & needed replaced & then my last one I had in for over 5 years & it was stil good nothing wrong with it however I was in that area doing some work on July 21st 2017 so I went ahead & installed a new one from ZZP just to be safe. So that's 7 years out of my 1st one & 6 years out of my last one which hadn't even gone out yet so how could my new one that is only 5 months old go out ? I included a pic below of the one that I picked up from ZZP & they claim that it's the same as OEM. I guess my other question would be if my thermostat is stuck open then why is it when I get off of the freeway my temps go from around the 130 range all the way back up to the 170 range where they should be & then it stays there ? If my thermostat was stuck open it would stay around 130 no matter what right ?

 

No, it all depends on airflow. On the freeway there is a lot of flow. When you get off, there is very little flow. Lots of airflow=more cooling. That's why you have fans, to create airflow through the radiator when you're not moving. A 180° (or 130°) delta (T2-T1 or ECT-ambient) is HUGE since they design them for 60° deltas. When you're not moving, that delta quickly approaches 0° since the temperatures equalize.

 

Man it's killing me to think it could be my thermostat, the part is cheap but it's a B to install! I don't know if this is related or not but my temp problems started when it got super cold out however at the same exact time I had just installed hood pins in my new CF hood. On the inside of the hood where we drilled the holes for my pins I have 2 good size holes. Could the hot engine air be getting trapped on the inside of my hood causing heat loss & the drop in coolant temps ? Probably a stupid question

 

I would say it's more likely that either you didn't notice a problem with the tstat when it was warmer out, or it is just really that cold and it's working as well as it can. It's free to test it (put it in boiling water), but as you said it's a pain to get to.

It's also possible that your new hood is allowing a lot of air to blow through the bay and is air-cooling your engine at speed.

 

I always test mine before I install. I've had a defective one out of the box before.

 

Your thermostat isn't shut. -40 or not, you will get heat. Run in recirc mode anytime you can. Why try to heat the outside air when you can reheat the inside air. Recirc doesn't work in defrost only mode.

 

Try covering a portion of the rad and see what happens. It's free and should help you diagnose the problem.

 

If the tstat isn't shutting, covering the radiator will increase the temps some.

 

Thanks so much for the help guys I can always count on my Cobalt family to help as far as not noticing my temps before I keep my dash set on the coolant temp setting all the time & I never change it so I'm always watching my temps. With my new CF hood it is a functional cooling hood however I have the panels closed for the winter so I wouldn't think that to much air is getting in. Thanks for the advice on blocking off some of the rad I'll be sure to try that as well.

I reached out to my tech who installed my last thermostat & he really thinks that it's just the cold air & not the thermostat but we will find out.

Hey what are your guys recommendations on letting our cars warm up before we drive them ? I know that with fuel injected cars you really don't have to let them warm up however I always let me car warm up for a good 5-10 minutes. My car is parked in my attached insulated garage but it's below freezing in there right now as well.

A couple of days ago I took a little longer than normal getting out the door so my car ran longer than I wanted it to & when I got out there the coolant temps had just reached 200 & the fans kicked on & dropped it back down to 180 like it should do so again that tells me that my thermostat should be good but I'm not an expert

 

HGT thanks man on the way home right now I will be sure to run on recirculation mode & see if that doesn't help

 

If it's stuck open, it'll take a few more minutes to get fully warm but it won't be much of a difference when it's just sitting. The difference is cruising in cool/cold weather.

 

2 minutes of idling is all you need for protecting your engine.

But when it's real cold my breath with will freeze the inside of the windshield and defrost isn't blowing warm enough to do anything.

 

So today guys I let my car warm up like I always do for about 7-10 min when I got out to my car the coolant temp was up to around 140 & climbing which is normal & then when I got out to the freeway rather then the temps dropping down to around 130-120 like they had been they actually kept climbing & within 2 min of freeway driving they were up to 171-174 where they should be & they stayed there for my entire 45 min all freeway drive into work ! The heater was blowing super hot air like it should be.

The crazy thing is it's even colder today (8% with a windchill of negative 20) than it has been all week.

So why did the temps act normal today when it's still super cold & I didn't do anything different ?

 

Thermostats can stick and release over and over again. Open and close one day and open and stick open the next. As long as your coolant is at the level it is suppose to be and continues to do this, the thermostat is at fault.

 

Thanks HGT I'm sure that's what it was doing. Very disappointing for a bran new thermostat! Well my hope is that she's no longer sticking because as I said my temps were perfect this morning for my 45 min drive to work when it was 9% out & now I just made my 45 min drive back home @ 6% temp outside & my temps were perfect again.

What are the chance that my thermostat just stuck on & off for those few days & now that it's no longer sticking it never sticks again until years later when I need a new one ?

Is it wishful thinking on my part that this was just a one time thing ?

 

I know there not fun to do as I replaced mine this summer but I would replace it the next time it acts up or this spring at the latest.

 

I'm in Canada and my temp is usually around 90 Celsius in the spring and summer. This past week, it's been -20 to -35 everyday and my temps go from 75 at a "warm up idle" to 68-65 when I'm driving lol. That's how cold the air is.