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2003 chevy trailblazer_lt_ext
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6 Posts
Discussion Starter · #1 ·
Hello everybody i am new to this site. i am haven overheating problems with my 03 TBEXT with the 4.2 and 4wd. At highway speeds engine temps are bout 205-210 but when i start hitting stop and go traffic the temp shoots up to 225-230. Iv replaced the thermostat had the fan looked at and tested and am looking for any advise on wat it could be anything would help.
 

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2003 chevy trailblazer_lt
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6,568 Posts
over heating.. typical hit list

1. thermostat
2. radiator cap is leaking pressure
3. water pump
4. fan clutch
5. block in radiator

not necessary that order... but those are the typical culprits..
 

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2003 chevy trailblazer_lt_ext
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6 Posts
Discussion Starter · #4 ·
ok i forgot to put this in the first post it only overheats when i turn the a/c on if its off its fine....oh and i changed radiator cap it fell apart when i went to pull it out.... i had it tested at a shop they said they hooked it up to there computer and test it.... they also said its a electrical clutch which sounds weird to me
 

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2004 gmc envoy_slt_xl
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10 Posts
I'm having the same problem with my GMC Envoy XL I6, the temp is aroung 230 - 235, I chnged the thermostat, water pump and flushed coolant, still the same, fan seems to working fine, could it be a radiator clogging?
I forgot to mention I also replaced the coolant temp sensor, and I'm not getting any error codes, no SEL.
 

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2004 gmc envoy_slt_xl
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10 Posts
I just went and checked the fan and tried to stop it with my hand and engine running hot, it stopped very easily, and after I let it go, it took a minute or two to go back to previous speed, is that an indication that the fan clutch is bad and needs to be replaced eventhough there is no SES light?
 

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2004 gmc
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26,181 Posts
I can't tell you that your fan is bad. I thought they wouldn't stop by hand, but reports are that they can be.

I need to confirm this with my own vehicle before I give any more advice like this.

For now, there is no perfect diagnostic except getting a scan tool to display commanded versus actual fan RPM when it's overheating and calling for full RPM.
 

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2006 chevy trailblazer_lt
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50 Posts
Whether or not it can be stopped by hand depends of a lot of factors. Since it is an electro-viscous clutch, it can engage at increments of 10%, instead of either being on or off, in the case of a full electric fan (a viscous fan is a whole nother story), so if the engine doesnt need the fan to spin at full velocity, the clutch may only engage at say 20% therefore you should be able to stop it by hand even if it is operating correctly. If the engine is hot and the A/C is turned to full blast the fan should be engaged all the way and you should not be able to stop it.

The only good way to test it is to have a OBD2 diagnostic tool where you can manually actuate the fan at each level to see if it spins up.

I would strongly suggest not sticking your hand into a spinning fan.

(I used to have an 03 TB LTZ that had a bad clutch. I tested it with our diagnostic tool at work.)

Generally if a overheats only on hot days in stop and go traffic, it is a bad fan clutch 90% of the time.

I was in stop and go traffic yesterday for about a mile and a half and saw three vehicles pulled over with steam pouring out and coolant dripping down. Your fan could be bad and you would never know until you get into stop and go traffic, or notice poor a/c performance at idle.)
 

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2004 gmc envoy_slt_xl
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I just changed the fan clutch and went out for a test drive, it's still overheating, what else could it be, I changed the thermostat, coolant temp sensor, water pump, radiator cap, fan clutch and flushed the coolant several times, nothing seemed to affect the temp, what's left that could possibly cause the overheating, I don't see any signs of a blown headgasket, no leaks, no oil in the coolant and no coolant in the oil, this thing is driving me crazy what could it be? Is it the radiator? how can I tell if there is a blockage in the radiator?
 

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gmc envoy_sle
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Having the same issue with a 04 Trailblazer LTZ. Just changed Radiator cap, Thermostat and Water Pump (what fun!) and it's still running at 240+ in traffic with the AC on. :mad: When it overheated the first time it pushed out all the coolant and appeared to use 3 qts of oil.. The fan clutch appears to be functioning normally and has not thrown any trouble codes. I think it's a bad head gasket, but there's no sign of coolant or water in the oil or vice versa. I'm going to get a coolant test done before I go any further I guess, to see if there are any exhaust gases in the coolant. Any other suggestions?
 

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2004 chevy trailblazer_lt
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997 Posts
Karwan, just a quick question. Do you do a lot of traveling on gravel roads?

The reason I ask is that I once saw a Tahoe that exhibited the same symptoms and it seemed nothing helped, no matter what they replaced. They went to a different mechanic who asked about the dusty road travel and when they said yes, he simply took the front grill apart, split the transmission cooler from the rad ... and the front face of the rad behind the cooler was just PLUGGED with dust.

There was nothing visible from either in front or behind.

Plugging in computers and reading codes sure help us a lot with problems but nothing still beats years of experience!
 
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