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2002 gmc envoy_slt
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Discussion Starter · #1 ·
Hey everyone, just replaced the fan clutch and serpentine belt on my 02 with 108K. Writeup on here was great and had some extra help from others on here. Great site!

I was headed to the airport yesteday for a trip to Asia for 3 weeks and noticed that the temp gauge was sitting on about 220 normally, not straight up at 210, and would rise to about 235 if I was on a slight hill climb.

I have bought a new thermostat, but havent installed it yet. I have RBarrios writeup saved on my desktop.

Do you think this is what is wrong, most of the posts on here that are T-stat related indicate that the temps are lower than the normal 210. I just want to be sure Im changing the right thing, not that it'll hurt probably needs replacing anyway....

Fluid level is good, checked prior to leaving, I had this issue plus the roaring prior to changing the fan clutch and was hopng it would solve both issues, apparently not...

Thanks in advance for your help, Barry
 

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Basic Vendor- Skid Plates
2007 chevy trailblazer_ls
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3,700 Posts
If you were moving (30-40mph or higher) when the temp was going up, it's probably the thermostat... Had a truck's thermostat not open all the way up once... It would close when it was cold, but would only open halfway when it got hot, so it would do what you describe... Going up hills and such, the temp would rise, etc...

Mike
 

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2003 chevy trailblazer_ls
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5,268 Posts
sounds like your thermostat is failing in the semi closed position.
Most of us here have them fail in the OPEN position.
You could also plug into your OBD port to read the temp the computer is seeing. It may be possible the stepper motor for the temp is bad (unlikely- but...)...
 

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2003 gmc envoy_slt
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7,190 Posts
Have you ever changed the rad. hoses? Hoses can get soft over time and as the coolant flows through, the hose will collapse. It's probably the t-stat, but at 108k and 7 years, IMO, the hoses should be changed.
 

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2002 gmc envoy_slt
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Discussion Starter · #6 ·
Temperature rising

OK, changed the t-stat today, also changed the Dex-Cool out as well. Idled the truck in the driveway for about 25 minutes, stayed just to the right of 210, but when I took it down the road it would again climb to 225-230 and stay there. I'm confused, I've replaced the fan clutch, t-stat, and fluid.
Is the next step the hoses? Is there a way to check to see if they have collapsed? Could it be a water pump?

Help. Barry
 

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Basic Vendor- Skid Plates
2007 chevy trailblazer_ls
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3,700 Posts
In this case, I'm going to go out on a limb and guess water pump or plugged radiator... You might start out with one of those "radiator flush/cleaning" additives, and do a flush and see what comes out...

What did the old coolant look like?

Mike
 

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2003 chevy trailblazer_ls
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You went to the trouble of changing the fan clutch and did not replace a $50.00 water pump, or the rad. hoses? I would replace the water pump, t-stat and hoses. Have not heard a lot about TB water pumps but in other alum. vehicles I have worked on the water pump vanes are steel and tend to disappear over time. Not rust just sort of go away. Did you check the old and new thermostat using hot water? You will need to run distilled water through the system until it is clear. You need to use distilled water with the Dex-Cool. I do not care what some here will say but NO NOT USE THE GREEN STUFF. Prestone Dex-Cool is fine. Has the Dex-Cool ever been changed? Flushing the rad is not a bad idea but what does the coolant look like now, and what does the stuff in the overflow look like?
 

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2005 chevy trailblazer_ls_ext
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You went to the trouble of changing the fan clutch and did not replace a $50.00 water pump, or the rad. hoses? I would replace the water pump, t-stat and hoses. Have not heard a lot about TB water pumps but in other alum. vehicles I have worked on the water pump vanes are steel and tend to disappear over time. Not rust just sort of go away. Did you check the old and new thermostat using hot water? You will need to run distilled water through the system until it is clear. You need to use distilled water with the Dex-Cool. I do not care what some here will say but NO NOT USE THE GREEN STUFF. Prestone Dex-Cool is fine. Has the Dex-Cool ever been changed? Flushing the rad is not a bad idea but what does the coolant look like now, and what does the stuff in the overflow look like?
:iagree: I just changed the thermostat on my 05, and I changed the hoses as well and flushed the system and refilled with Dexcool. My engine and radiator looked very clean, so I figured if it worked fine for 4 1/2 years and 50K miles why not use the same stuff!
The hoses are relatively cheap, less than 50.00 for both. The hoses LOOKED okay, but I usually prefer to err on the side of caution. Much cheaper than buying a new engine.

I always check a new thermostat in a pan of hot water to make sure it opens at the correct temp before installing it. On vehicles like the TB it is too much work to risk putting in a bad one and then taking it out again.

If (or maybe I should say when) my fan clutch goes out again - I will replace the water pump at the same time. The dealer replaced my fan clutch 2 - 3 years ago under warranty.

Back to the o/p's problem:
I also agree this is starting to sound like a bad water pump. Like it's pumping enough to cool at idle, but not enough to cool at higher speeds. Collapsing hoses are also possible. Not many other possibilities left! :D
 

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2004 gmc envoy_sle
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399 Posts
I haven't had this problem with my truck yet, but just by reading your posts, it sounds like the issue started after you replaced the fan clutch. Maybe that part is bad or the sensor for it?:m2: What was it doing before you replaced it?
 

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2002 gmc envoy_slt
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Discussion Starter · #11 ·
Temperature rising

OK, still fighting this issue. Car is constantly at 225-230. I have checked temp with an IR thermometer at the hose leading into the rad, coming out of the rad, and at the tstat. Nothing looks out of the way and seems to be significantly lower than what the gage is reading. I have an appointment for a local service guy to look at her on Wednesday. Ihave bought a new temp sensor for them to have. If you had to guess what is the most likely candidate? Maybe put them in order. I am leaning toward a bad sensor.
Thanks for your time and efforts.
 

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2003 chevy trailblazer_lt
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I would say water pump!! They are natorious for going bad on the TB's, not to the point that they leak and dont work but the bearings inside go bad and it gets loose and make a lil noise.
 

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Discussion Starter · #13 ·
Temperature rising

And what does the water pump sound like? This is an 02 Envoy. I do notice that when the truck slows down into first gear it gets kinda loud until the RPM move up, nothing like the airplane roar of the FC as I heard before replacement but almost like it when it kicks down in gear. I also could be scruntinizing more than normal as well.
 

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2003 chevy trailblazer_lt
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And what does the water pump sound like? This is an 02 Envoy. I do notice that when the truck slows down into first gear it gets kinda loud until the RPM move up, nothing like the airplane roar of the FC as I heard before replacement but almost like it when it kicks down in gear. I also could be scruntinizing more than normal as well.
Kind of like a dry bearing going bad..
 

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2002 gmc envoy_slt
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Discussion Starter · #15 ·
Coolant temperature Rising

OK....Thanks everyone for your replies. Finally got this thing straight. Replaced the water pump, running right where she should at 205-210.

Could kick myself in the rear for not replacing the water pump while I had everything apart replacing the fan clutch, but live and learn. Problem is fixed so all is good.

So, Overall I replaced the fan clutch, thermostat, temp sensor, and then the water pump. Also replaced the serpentine belt for kicks while I was in there.

Put 4 new tires on the beast and hopefully, I don't have to touch her for awhile........

Thanks for all your help and nice instructions. Barry.
 
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