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2004 chevy trailblazer_ls_ext
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Discussion Starter · #1 ·
Someone Help... Please.

Automobile:
2004 Chevrolet Trailblazer EXT, V6

Problem:
Over Heating, AC only works on freeway.

Already Tried…
• I replaced the thermostat and fan clutch with new ones.
• Fan clutch was diagnosed as the problem at Econolube.
• I can’t see any signs of leakage anywhere.
• The new fan clutch doesn’t seem to be doing anything different from the old one. It rotates at the same speed as the water pump pulley at all times (does not go any faster even after running car for a little while). Can there be something wrong with the electrical from the computer to the fan clutch?
• I watched the fluid in the radiator while car is running to see if the fluid is moving. I was told that this lets you know if the water pump is working and if there is any blockage in the radiator. It seems to be flowing fine. When the car heats up the fluid goes down and flows.

It seems like the fan clutch is the problem since it doesn't move any faster to cool down the radiator. Any ideas?
 

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2004 gmc
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There is a fuse and a relay involved in having the computer control the fan clutch. Can you try to use a rag (carefully) to stop the fan from rotating at idle?

Check fuse #20 under the hood. Interchange relay 45 with the identical one (46) next to it that runs the headlight low beams.

What brand of fan clutch did you install?

Can you inspect the five blades in the wiring harness going to the fan clutch to make sure you don't have a broken/bent one?

How about the wires in the harness from the connector to the center of the clutch? Any chafing?

Has the SES lamp ever come on, and has it ever set a code that needed to be read, such as what Econolube did maybe? Do you have the exact code they read? It's the only way to be certain we're on the right path.
 

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2003 gmc envoy_slt
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:tiphat Welcome :tiphat . :iagree: And just a side note the fan is turned by the water pump. It can't go any faster than the pump. Except, MAYBE, when you're driving.
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter · #4 ·
:thx Hey Roadie, thanks for your help; here's the answers to your questions.

I was able to use a rag to stop the fan easily.

The fuse is good and I swapped the two relays and did not notice any changes.

The new fan clutch is a Dorman P/N 622001.

All of the wiring and plugs look to be intact.

The SES light did come on yesterday during the test drive after changing the fan clutch. Although, after completing the steps above this morning, I test drove again and the light was not on anymore.

During my test drive this morning, I noticed the following:

It took much longer to heat up than yesterday. Around 20 minutes and after turning the AC on. It got up to the 3/4 mark on the temperature gauge before I turned the vehicle off. Altough, the wheather was not as hot this morning as it was yesterday afternoon. When I got back from the drive before I turned the vehicle off, I popped the hood and noticed that the fan was not turning at all. I then found that the fan shroud was not sitting in place perfectly and was rubbing against the fan. After properly seating the fan shroud, I turned the vehicle back on and the fan was turning. I was still able to stop the fan easily with my hand and a rag.:confused:

What should my next troubleshooting steps be?

We're not doing very well with money right now, so I'm trying to do as much as I can without taking to a mechanic. Thank you all for your help, it is very much appreciated.
 

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2004 gmc
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If you can stop the fan with your hand and a rag, it's either bad, or the electrical control to run it is not working. Do you have a meter and know how to use it?

The Dorman may also be bad. Did you get it locally or mail order?

The fan wiring harness is as follows:

A - Black - ground
B - White - fan supply voltage (should read 2-12V with a meter - will vary)
C - gy/wh - ground
D - d-bu - speed sensor (only small voltages here, don't bother reading with meter)
E - gy - 5V reference voltage for the speed sensor
F - not used
 

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2002 chevy trailblazer_lt
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Heating engine,

2002 TrailBlazer LT 4x4.
I have a similar problem,
radiator tank & coolant is changed but still the car heat needle goes upto 3/4. (not exactly, its about 2 lines after the half, u can say in the middle of 1/2 & 3/4)
while driving its on half.
I will however try today this fuse & relay thing.

Mr. the roadie,
stopping the fan with hand(rag), is it a correct test to check the fan clutch ?or any other idea ???

regards,

/SA
 

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2004 gmc
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Stopping the fan is only a good test if the engine is HOT and overheating. The fan doesn't need to spin fast when it's idling. It actually takes a long time to get to 210 degrees F when you're idling.

A better test is with a dealer's tech tool or a good scan tool that can see the data of the COMMANDED fan RPM and the ACTUAL fan RPM. If the engine is overheating, and these numbers are not the same, then there's a problem.

You may also have a bad thermostat, collapsing hoses, or other problems that cause overheating.
 

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2004 chevy trailblazer_ls_ext
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to original poster, if you haven't already done so, check the CAL of your ECM, there was a TSB for this problem, I had a similar problem it did take care of it somewhat, however, after doing some hands on testing... you can try this next time it gets hot... if you are driving and then come to a stop, is this the point where you see your temp gauge creeping up? if it is shift your tranny to neutral and see if that drops your temps...
 

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2002 chevy trailblazer_lt
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Heating engine,

OK guys,
I tried the relay thing,,, nothing happened.

now I will try to change the radiator water, since it is the cheap solution at the moment, and if that doesnt work, then I have to change the fan clutch.

Original Fan Clutch should do the trick, right !!!

Finally I just wanna ask that is there any other thing that I should look before I go with the change clutch option ?

:undecided
 

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2002 chevy trailblazer_lt
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2002 Over heating - new radiator, new fan clutch, new thermostat

I've changed the fluid, installed a new radiator, new fan clutch, 2 new thermostats, and still have the same problem; on hot days going up an incline or rapid driving, the temp goes up 3 marks past center. Mechanic said at that point the water temp was still within specs. Mechanic said I may have a cracked head. I've read th post on some other possible fixes and I'll try them when the weather heats up again.
 

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2002 Over heating - new radiator, new fan clutch, new thermostat

Themechanic said he could feel water in both the lower and upper hoses so he did not replace the water pump, but that seems like the next most logical step. Thanks for your help.
 

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temp needle 2 marks pass middle....

Well now when I changed the fan-clutch,,,
there is a bit of change in behavior, but still the temp needle goes upto 3 marks from center, (as u said).
but when I accelerate, it comes down to middle, (that wasnt happening before)
 

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2002 gmc envoy_slt
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3,203 Posts
If my gauge goes one needle width past 210 - straight up - I get worried and watch the scangauge like a hawk to see the true ECT. Very odd dealer that would say three tick marks is OK.
You have to remember that GM dumbed down the gauge somewhere along the line. On the '02s, they actually MOVE! - At 2.5-3 lines over, my Dynoscan is showing a coolant temp between 218-220, which isn't going to hurt anything. Of course if I lightly rev the motor, the needle drops like a rock back to just before the 210 mark. Its been that way since before the e-fans went in and the thermostat was replaced. (It hung open and I couldn't achieve the nearly 210 with the a/c on after installing the fans). I'm convinced a higher flow pump would keep it just before the 210 mark.
 

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Problem solved....

Gentlemen,
This is my experience of solving the problem & I would like to share.
I had heating problem in my T-Blazer,
I changed Thermostat, Fan Clutch and all other related parts but not much difference.
Then at the end my mechanic told me to leave the car and when I got it after a week, the heating problem was over.
When asked, he told me that the car's engine was heating because of it "HEAD" he removed the complete head and valves, got them grind and put a new Head Seal" and that's it.

So if your mechanic is telling you something about Engine head, then it can be true.

Mechanic have to open the engine head
and valves
clean them
Get them grind if required
put a new head seal (necessary)
and fix it back professionally.

by doing those steps, im sure the heating problem will be solved.

BUT... this is an expansive work, so try to do small things first (such as cluch & thermostat) if they dont work, then you may start opening the engine head.

I hope this will help.

Take care & thank you all for your support.

regards, :thx
 

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2003 chevy trailblazer_ls
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Overheating 2003 trailblazer

HI,
I have a 2003 trailblazer and I replaced the water pump about 3 months ago because it started leaking, also replaced thermostat. I was working fine till yesterday. I live in arizona and temps. get up and over 113. Yesterday was around 109, but like I said no probs till yesterday. it overheats and goes over into the resevoir and bubbles out. I was wondering if it could be the fan clutch or just a clogged radiator. When running on the open road it still is hot, does not seem to cool down much stays at 3/4 on the temp. gauge. Any ideas would be grateful. Thanks, Robert
 
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