Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

1 - 16 of 16 Posts

·
Registered
2004 chevy trailblazer_lt_ext
Joined
·
20 Posts
Discussion Starter #1
2004 Trailblazer Ext, 4.2L
Hello everyone.

About 2 weeks ago my Check engine light came on; I stayed on for around 2 days and went off. I got to an Auto Zone after it went off and had the code read, they said the code that came up was for low coolant temp, during this whole time my temp gauge read almost right at 210.

Then 2 days ago it when it was about 90deg out I was driving up some small hills on a back country road and the temp gauge went up to 230 and a little past, when I would drive on flat or park it would come back down until I went up another hill, let me also add during this whole time the a/c was running. I took it to the dealer to get serviced they couldn’t duplicate the exact problem however they said it was running a little over 210. They suggested that it was the thermostat, from reading some other post on here I asked them if it could possibly be anything else such as the PCM coolant temp sensor, computer update, the fan-clutch or a blocked Radiator, the dealer told me that he has never seen those replaced in a vehicle with my age (2004) or mileage (96,000) and told me his feelings are that it’s the thermostat.

So I had it replaced and picked it up and took it for a little country drive up my hills and the gauge again went up to 230 again I drove it with the A/C on and the outdoor temp was 95. I called the dealer back and said that it was still going up. And they told me that 230 was within normal operating temp., they could not answer why in the past 4 years it has never gone above 210, the only time it has gone above 210 is when I am pulling my 3,500lb trailer, but never 230. I then also tried my route with the A/C off and the temp stayed at 210. While 230 isn’t taking it to the red line, My worry is, if it’s going up to 230 not pulling anything it will over heat if am pulling.

Does anyone have any Ideas that I could try. Thanks for your help in advance.
 

·
Registered
2002 chevy
Joined
·
2,582 Posts
There are several causes of overheat engine:

1) Low coolant
2) Hole in the radiator
3) Bad Thermostat
4) Bad fan clutch
5) Bad heads
6) Bad head gasket
 

·
Registered
2004 chevy trailblazer_lt_ext
Joined
·
20 Posts
Discussion Starter #4
Thanks, the radiator was flushed October of last year.
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
They suggested that it was the thermostat, from reading some other post on here I asked them if it could possibly be anything else such as the PCM coolant temp sensor, computer update, the fan-clutch or a blocked Radiator, the dealer told me that he has never seen those replaced in a vehicle with my age (2004) or mileage (96,000) and told me his feelings are that it’s the thermostat.
All I can say is.... :dielaugh::duh::crazy: Either that or the dealer doesn't
do much service work on these vehicles...and there might be a reason for
that.. :undecided Outside of that, he's either blind or lying... OK...maybe
that's a little harsh...but *"never"*?! Fan clutch issues are common, and at least for the
2002's there were a few updates that affected the fan operation, so PCM updates
aren't uncommon either.

That being said, thermostat *is* pretty much the most likely suspect. That
sort of over heat behavior is not really indicative of the coolant temperature sensor.

Buc Nasty's list is pretty complete. I would add to it a check of the
*exterior* of the radiator. If the lower cooling fins are getting clogged,
that would reduce the effective radiating surface available.

If you have the transmission cooler, make sure it's clean as well. If it
isn't, the extra heat from the transmission can jack up the overall operating
temperature.

Did you do the radiator flush, or did you have it done? There's always a
possibility that there's some contamination that got into the system
and is clogging some of the tubes. I'm assuming 50/50 Dexcool/water was
used? How's the water pump? If it's not pumping effectively, normal
driving might not push it over the edge, but towing might.

Also, how's the maintenance on the truck? Transfer case fluid good, changed
at 50K? Transmission fluid/filter good/changed? rear diff checked? Not that
these would specifically overheat the vehicle, but with the added load of
a trailer, *any* item that isn't working smoothly can make the engine
work harder and hotter.

Those temperature ranges are supposedly within spec, but if it wasn't doing
it before, and suddenly *is*, that would have me questioning things as well.

Good Luck!

Chris
 

·
Registered
2004 chevy trailblazer_lt_ext
Joined
·
20 Posts
Discussion Starter #6
The Dealer is a GMC dealer, so I thought they would have worked on GM vehicles before.

As for the thermostat that’s what they replaced, and the problem continues, As for the flush, I did it and every as worked fine since. In July we had temps that got In to the 100s and I didn’t have a problem. I also requested the dealer check all of the rest of the fluids yesterday, every thing is normal.

To double check and make sure there are no blockages in the radiator I am going to pick up a laser thermometer and will check for cold spots tonight.

My thought process is since a got a “coolant temp to low” code that perhaps the sensor is bad and thus telling the fan to spin at a slower speed or not to compensate for the A/C

Thanks again
 

·
Registered
2004 gmc envoy_sle
Joined
·
132 Posts
use some compressed air to blow anything out of the cooling fins on the radiator and/or a/c condenser
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
The Dealer is a GMC dealer, so I thought they would have worked on GM vehicles before.
Well, yes, but it wouldn't be the first time someone here has been told
something along the lines of "that never happens" or "we *never* see
that". ;) I think it's the "never" part that got me going...

As for the thermostat that’s what they replaced, and the problem continues, As for the flush, I did it and every as worked fine since. In July we had temps that got In to the 100s and I didn’t have a problem. I also requested the dealer check all of the rest of the fluids yesterday, every thing is normal.
Yep, I understood that. I was just agreeing that generally speaking, that
*is* the most likely culprit, so the dealer wasn't actually off base on that.

To double check and make sure there are no blockages in the radiator I am going to pick up a laser thermometer and will check for cold spots tonight.
Great idea! I need to get one of those myself.

My thought process is since a got a “coolant temp to low” code that perhaps the sensor is bad and thus telling the fan to spin at a slower speed or not to compensate for the A/C
Do you have a scan tool that can tell you what the PCM is actually
seeing as the engine operating temperature? The gauges are not really
dependable indicators. The sensor is a good point. If the PCM thinks the
engine is cooler than it really is, it won't call for the fan clutch to engage.
This *won't* trigger a code if it's within a certain range, and the PCM
won't really think anything is wrong, but you won't be getting optimal
air flow for the conditions. The PCM should be including the AC being on
in the adjustments.

Do you have a shop manual? I don't have mine in front of me, but on
previous vehicles, there's been a small chart of resistance vs temperature
values for the coolant temperature sensor. It might be that yours is
only unhappy in a certain range. Worth a check with a multimeter.

There is always the chance that the thermostat is bad out of the box.
If you can get access to a scan tool, you might check to see if there
are any pending codes.

Cheers-

Chris
 

·
Registered
2004 gmc envoy_sle_xuv
Joined
·
52 Posts
over heat

This may sound out of order but my son had a VW Jetta with the very same problem. It finally quit and went into total catastrophic failure. Blown head gasket, coolant in the oil, brgs wiped out, warped head, and last but not least water pump tied up. Total cost aprox. $2,000.00:bonk::hail::duh:
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,298 Posts
This may sound out of order but my son had a VW Jetta with the very same problem. It finally quit and went into total catastrophic failure. Blown head gasket, coolant in the oil, brgs wiped out, warped head, and last but not least water pump tied up. Total cost aprox. $2,000.00:bonk::hail::duh:
Not out of order at all. Buc Nasty listed the possibility in post #2. Hopefully it's
*not* that! My second S10 had a head gasket failure, but it would overheat in
a different pattern than what Canz described, so I'm hoping it's something less
drastic.

Cheers-

Chris
 

·
Registered
2004 gmc envoy_sle_xuv
Joined
·
52 Posts
Leaking S-10

I had a 99 S-10 and at 12,000 mi the intake gasket failed. Noticed loss of coolant with none on the floor. It was going in to the oil. Heard a lifter rattle on startup. My neighbor who is a fork truck repairman said th 4.3 v6 was noted for that. GM fixed it under waranty .:hail:
 

·
Registered
2004 chevy trailblazer_lt_ext
Joined
·
20 Posts
Discussion Starter #12
Ok, I have ran it a few time with my scan tool and the ECT sensor is reading the same as my gauge. I also checked the radiator with a laser thermometer and was unable to find any gross differences (Cold Spots). However it doesn’t happen with a/c off. Thanks
 

·
Registered
2002 gmc envoy_slt
Joined
·
3 Posts
hello you all
I am a certified green leaf shade tree mechanic [and a BS'ser though title sounded impressive:) I was wondering if there is anyway to check the fan clutch to see if it is operating correctly didn't know if it turned on when the air is on I replaced the thermostat 2 weeks ago and its been working fine but yesterday it overheated again on my wife it above 90 degree outside temp she said it went in too the red thanks in advance.
 

·
Registered
2005 isuzu ascender
Joined
·
319 Posts
With the car OFF. When engine is cold, it should spin pretty freely. If hot it will have friction.

If it was in the red, what were conditions? ...idling vs driving on highway...
 

·
Registered
2005 chevy trailblazer_lt_ext
Joined
·
3 Posts
I've replaced so many fan clutches on these, usually they come in the shop either making a ticking noise, or with trouble codes for cooling fan. I always flash the software update for improving fan performance, makes it come on stronger and quicker.

Sent from AutoGuide.com Free App
 

·
Registered
2004 chevy trailblazer_lt_ext
Joined
·
20 Posts
Discussion Starter #16 (Edited)
hello you all
I am a certified green leaf shade tree mechanic [and a BS'ser though title sounded impressive:) I was wondering if there is anyway to check the fan clutch to see if it is operating correctly didn't know if it turned on when the air is on I replaced the thermostat 2 weeks ago and its been working fine but yesterday it overheated again on my wife it above 90 degree outside temp she said it went in too the red thanks in advance.
I don't believe so, with out a Tech II "Dealer Computer" Mine still runs hot, but has never "Overheated" I have replaced the thermostat, 3 fan clutches, Radiator and Water Pump and now i have a manual bypass that turns the fan on full blast, and the temp goes down quickly. This past weekend I was towing my boat on a 3 hour trip a/c blasting and temps around 90 and she would ride half way between the 210 mark and Red, occasionally I would activate the bypass to give it a break.

here is the link for the bypass http://forums.trailvoy.com/showthread.php?t=59086

Also use a laser temp tool and see if you have any cold areas of the radiator when its at normal temp, to see if its partly clogged.
 
1 - 16 of 16 Posts
Top