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Discussion Starter · #1 ·
Is it just my vehicle, or is the 1st generation Colorado with a 3.5 liter engine problematic in that in Winter months, the cabin heat doesn't really get toasty hot?

I have to run my vehicle for a bit to thaw out steamed windows and occupants complain that they are cold. It has been like this for at least 6 years now. I get heat in the winter, it is just not HOT. I honestly don't remember what it was like when it was new. Someone said it could be the engine mount sensor (if there is such a thing). I've heard other ideas too, all of which sound equally expensive to repair.

Any thought and what was your experiences?
 

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I'll second bac522. Thermostat failure is kind of common for 1st Gen trucks. Your temp indicator should be about midrange when the engine is warmed up.

Depending on the maintenance history of the cooling system, fondupot has a good point also.

There is no "engine mount sensor" that will control the heat. The coolant temp sensor only reports the temperature.
 

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Discussion Starter · #5 · (Edited)
First thanks everyone for your input. I know at 143,000 the truck isn't new anymore, but let's just say I have my fair share of issues and failures with far fewer miles than many other Colorado owners. I still like the truck and it is far cheaper than a new truck...but I need to know what I am up against for repairs.

#bac522, I did not know about such a sensor before, so thank you. Literally at 15 degrees or less, I must have the heat on high AT ALL TIMES. After the engine warms, the inside warms up "a little" On the coldest days at or below zero, I use just the defroster and foot warmer so I don't lose feeling in my feet! I'm pretty sure the truck was not like that when new.

#fondupot & #cart7881, I don't know if I should try that sensor first and then look at flushing the heater core out. I can remember about 7 years ago the 1-4 fan speed selector only ran on the 4 setting in the heat of the summer and I had to go to the stealership at the time as I needed it fixed and fast. It was only working on setting 4. I think they replaced the electronic round control, but also had to either flush fluid of something else behind the dash that took them hours to do (over $700 bill). They may have flushed something out but I truly don't remember. My old Blazer had issues with fluid "in the cash" too, causing gurgling sounds when accelerating. Maybe this fluid flush of the core that you are talking about is the same type of thing.

I'm glad you know there is no engine mount sensor. Someone must have been pushing a line of BS to me at the time! I'm going to get this issue sorted in a few months and will post the updates here for anyone that might want to know and to help diagnose similar problems in their Colorado. Thanks again.
 

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Discussion Starter · #6 ·
Might want to consider replacing the engine thermostat. If it's stuck open then it won't allow the engine to heat up the coolant. What does the temperature gauge show when you're driving?
The temp gauge generally gets to just under the 1/2 way line on the dash when the engine is warmed up. It has been consistent since like that since I bought the truck new. I don't think it has even gone over the 1/2 way mark. Does that mean it may not be the thermostat, is is it a different thermostat than the one that shows on the dash?
 

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It's been awhile since I had my 2005 Canyon, but I recall having to replaced my engine thermostat. It's fairly easy for any shop to do. It's not a sensor per say, but a mechanical device that opens up at a certain temperature. Basically the engine thermostat opens up at (going off memory) around 160 degrees to cool the engine. This same coolant (which absorbs the heat of the engine) cycles through your cab heater core and that's where the heat comes from. It's possible that sludge is blocking the heater core in the cab. I think at a 140K miles probably wouldn't be a bad idea to have a garage check out our thermostat and do a full flush of the coolant system which if done right will flush the heater core.
 

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Agreed with everything thats been said but let me add this....the 5 cyl is a royal pain in the ass to bleed the air out and the heater core is very prone to be air bound.

After changing out the thermostat, it may take awhile of constantly squeezing the heater and radiator hoses to get the air out but rest assured, your 2005 should not only be toasty, but mildly uncomfortably hot when its working properly.

Good luck with yours and let us know how you make out. :smile2:
 

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Discussion Starter · #9 ·
I looked at the overflow tank, and it still has a pale pink tint to it. The overflow tank itself is at the correct full line, which is good. There is some crusties that have built up along the fluid line inside the tank (I think I have seen this on every vehicle as the miles roll on) and the very top of the fluid seems to have some tiny dust-colored particles on it...nothing to worry about...but definitely a sign I should get a coolant flush and blow out. Hopefully that will get my heater core nice and toasty again!
 

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Have owned both a 2005 and 2010 Colorado and they both put out plenty of heat. You could check to make sure the cable for the temp and heat/cool settings is properly connected under the dash. I have read where one came loose or a bracket broke and the cable was not completely moving the HVAC door.


Other than that:

Change thermostat. . .

Disconnect heater hoses at firewall. . . . back flush in reverse flow direction then forward several times.

Also flush entire cooling system.

Replace with 50/50 Dexcool coolant.
 

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Discussion Starter · #11 ·
Given everyone's advise here, I am getting the coolant system flushed and refilled for the first time since the truck was new (over 140,000 later). Hopefully that does the trick. I need HEAT, not "warmth"! And winter is soon approaching. Hopefully the repair shop can get the heater core working properly on the first try, but even they admitted it may take several tries. I told them a few tricks already stated here.
 

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Given everyone's advise here, I am getting the coolant system flushed and refilled for the first time since the truck was new (over 140,000 later).
Didn't know that part and that is 40K too long! You should flush the system around the recommend 100K mark. There is corrosion inhibitors in the coolant which is why you should flush the system at the recommend intervals or you run the risk of needing new radiator/heater cores. And have the shop confirm the engine is operating in the recommended temperature range, they can get more precise readings from the OBD2 connector then what the analog gauge shows. I still suspect that the engine block thermostat is the issue...I remember on my 2005 having to replace mine around the 140K mark.
 

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Discussion Starter · #14 ·
Thanks again for the tips. The service garage has not got to it yet...but they did say older variants of GM Dexcool caused corrosion, blockages and general issues on it's own. Yeah...it is a good thing I am getting it flushed. Hopefully that alone will do the trick. I will tell them to check the thermostat if they do not see an improvement in cabin heat. The gauge has read in the same about 1/4 - 1/3 heat range during normal operation since I got the truck new..but maybe the gauge is not accurate. I will post updates when I get them.
 

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Discussion Starter · #15 ·
Greetings all. After another trip to the repair shop to fix leaking from axle shafts, I told the tech to check the thermostat given we just replaced the coolant a few months ago.

He checked the temperature of the coolant when running and indeed it was not hot enough. He changed out the thermostat and voila! I won't have cold feet anymore this winter!

I just wish the Colorado had the temperature displayed on the gauge and not just "cold to hot"...not very helpful for diagnosing things like this!
Thanks everyone for your input.
 
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