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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 06-16-2017, 01:27 PM
EnvytheEnvoy EnvytheEnvoy is offline
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2002 GMC Envoy SLE
Majestic Red Metallic 4.2L I6 4X4
Join Date: Jun 2017
Location: Flint, mi
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Strange overheating issue

Just bought an 02 envoy 4.2 i6 for cheap. Guy didn't know anything about anything, long story short bad furl pump relay and now it's up and running.

The problem I'm having though is this: it'll take a good 15-20 minutes to reach temp (210) then hold there for about 2 minutes, and then all of a sudden start climbing rapidly. Now I've never let it actually get in the red, always shut it off at about the 3/4 mark on the gauge. At that point I can hear bubbling in the overflow tank slightly. Compression test and leak down test has been done, as well as a chemical test for gasses in the radiator and everything comes back good.

My first thought is the thermostat isn't fully opening, but I'm not so sure. The fan clutch engages, but it also does have a slight wobble to the fan as well so possibly the waterpump going.

I just don't get how it goes from taking forever to reach temp, no matter if idling, revving, or driving, and then all of a sudden just shooting up in temp so fast. It will hold at 210 for about 2 minutes after taking 20 mins to get there, then 2 minutes later if I let it go it would be in the red.
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  #2  
Old 06-16-2017, 08:29 PM
JLS1950 JLS1950 is offline
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2005 Chevy TrailBlazer LT
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My 04 TB did that and it turned out the thermostat was stuck half way. Replaced and that resolved the issue.
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  #3  
Old 06-17-2017, 12:09 AM
EnvytheEnvoy EnvytheEnvoy is offline
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2002 GMC Envoy SLE
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Originally Posted by JLS1950 View Post
My 04 TB did that and it turned out the thermostat was stuck half way. Replaced and that resolved the issue.
I was thinking about replacing that anyways just to be safe. Hopefully that'll take care of it.
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  #4  
Old 06-17-2017, 09:14 PM
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vipergg vipergg is offline
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Get one from the dealer even if it cost more. People have had issues with OEM replacements .
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  #5  
Old 06-19-2017, 03:20 AM
EnvytheEnvoy EnvytheEnvoy is offline
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Get one from the dealer even if it cost more. People have had issues with OEM replacements .
Thanks, but no thanks. I'll go with a $20 stant with a lifetime warrenty over the $100 the dealer wants with a 30 day return any day.
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  #6  
Old 06-19-2017, 11:32 AM
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AWD V8 AWD V8 is offline
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Originally Posted by EnvytheEnvoy View Post
Thanks, but no thanks. I'll go with a $20 stant with a lifetime warrenty over the $100 the dealer wants with a 30 day return any day.
I've always used Stant. Over 45 years and never had any issues....until my I replace the thermostat on my Envoy when I did my rad fan. My temps would rise occasionally when pulling my loaded trailer on warm days. I replaced the fan and the thermostat. Now the engine would run hot on a cool day, with no trailer. I was puzzled as to why it was worse now, was the new radiator fan defective? I ended up replacing the rad, no change. I removed the Stant thermostat and dropped in a pot of water and heated it on the stove. It looked like it was opening as it should. The Stant cost me under 20 bucks but I wasn't going to put it back in as I didn't trust it. I spent the $70 for the dealer thermostat and no more cooling problems.

And this isn't just my experience, others on the forum have had the same experience. I'm all for saving a few bucks, but sometimes the aftermarket doesn't get it right.
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  #7  
Old 06-19-2017, 05:18 PM
EnvytheEnvoy EnvytheEnvoy is offline
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Quote:
Originally Posted by AWD V8 View Post
Quote:
Originally Posted by EnvytheEnvoy View Post
Thanks, but no thanks. I'll go with a $20 stant with a lifetime warrenty over the $100 the dealer wants with a 30 day return any day.
I've always used Stant. Over 45 years and never had any issues....until my I replace the thermostat on my Envoy when I did my rad fan. My temps would rise occasionally when pulling my loaded trailer on warm days. I replaced the fan and the thermostat. Now the engine would run hot on a cool day, with no trailer. I was puzzled as to why it was worse now, was the new radiator fan defective? I ended up replacing the rad, no change. I removed the Stant thermostat and dropped in a pot of water and heated it on the stove. It looked like it was opening as it should. The Stant cost me under 20 bucks but I wasn't going to put it back in as I didn't trust it. I spent the $70 for the dealer thermostat and no more cooling problems.

And this isn't just my experience, others on the forum have had the same experience. I'm all for saving a few bucks, but sometimes the aftermarket doesn't get it right.
I agree sometimes they don't get it right, but I honestly don't have the money to waste like that. I have about $150 to figure out this overheating problem. My local dealer quoted me 100 on the thermostat itself, and the next closest dealer is 2 hours away.

I'm going to have to take my chances on an aftermarket one...honestly I'll have to take my chances on all aftermarket parts for the cooling system if needed. The good thing is that I'm highly mechanically inclined, and I do have a few tricks to narrow it down.

Kind of sucks that the thermo is built into the housing like it is, makes things difficult to a point. I do have a friend parting out a tb, and he has a known bad thermo he was going to give me for testing purposes.

I know what ya'll are thinking, how does a bad thermo (stuck closed) help? Well I figure i can disassemble the thermo itself so it free flows fully, stick it in and run the envoy, and see what my temps are. We're having very hot days right now here in mi, so I figure if I can keep it under or on normal temps in this heat by doing that then it is the thermo and not the wp, or the fan clutch slipping.

It would also save me from hollowing out my oem thermo in case it is good. Any step I can take to ruling out parts so I don't have to replace helps a lot. If I can narrow it down to one part 100% then I can get oem, but if it's a combination or I have to guess then I'm going to have to go with aftermarket and hope for the best.

I mean honestly I only paid $300 for the envoy. If I get it going rightin my budget awesome...if not I part it out and make my money back and then some. Just sucks having to pick and choose. If I had the extra cash I would just replace all 3 so it's done and over, but such is life.
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  #8  
Old Yesterday, 12:06 PM
JayG83 JayG83 is offline
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Fan clutch will not engage

Hello everyone, New to the site but have read tons of helpful information. My problem is one day I was driving my tb doing about 75 on the eway then my reduced engine power came on but I was still able to drive normal speeds without any power reduction. Got home shut the tb off and the rep light went away but my sel light was on. Pulled codes and said my fan clutch was the problem. So now I have been driving it for past eight months and it has been fine now all of a sudden my reduced engine power has been kicking in after driving for about two miles I will turn the ignition off restart the TB and it will be fine for a little bit longer and then kicks back in again until I restart it remind you the past eight months it has been perfectly fine and running decent but my fan clutch has not been kicking in it has been turning to where I can basically count the blades on the fan as it's running. Any advice would be very grateful and I am trying not to pour money in this thing is it is already becoming a money pit
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  #9  
Old Yesterday, 02:06 PM
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EnvoyBoy2004 EnvoyBoy2004 is offline
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Before condemning the fan clutch you need to check the wire harness going to it. There is a 5V reference voltage that is used by the fan clutch and throttle body sensors. If that voltage is interrupted, it could set the REP indication.
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  #10  
Old Yesterday, 02:21 PM
JayG83 JayG83 is offline
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2004 Chevy TrailBlazer LT
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How do I check that?
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