Question about 2002 GMC Envoy

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Replace the thermostat on 2002 GMC Envoy

How do I Replace the thermostat on a 2002 GMC Envoy. Also, if the top radiator hose in hard with pressure, is this an indication the thermostat is bad? Is the thermostat located on the engine end of the top radiator hose?

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  • 341 Answers

4.2L Engine the thermostat and the neck where the hose goes on is one unit $25 at autozone

  1. Remove the necessary coolant from the radiator.
  2. Remove the alternator, Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
  3. Remove the thermostat housing bolts.
  4. Remove the thermostat housing from the engine block.
  5. Clean all of the surfaces of the thermostat housing.
  6. Clean the sealing surface of the engine block.

Posted on Dec 29, 2008

  • Mark Cooper May 10, 2012

    I have a 2002 Envoy that has the outlet hose on the right sid by the oil pump. The thermostat is not in this area, Where is it?

  • clint_stark
    clint_stark Feb 18, 2013

    The thermostat is built into the driver side radiator hose neck. I have never seen this type installation. You wil need to remove the alternator to access rge bolts. I replaced my because it was showing a code number 028 , might have been 128. Two of the possible causes for the code werw thermostat and coolant temperature sensor. I managed to break the coolant sensor off in the block as I was not able to locate the proper tool. I was able to remove the remaining threaded area with an "easy out". It ia a reverse twist bit that can be tapped into the hollow tube where the actual sensor was located. The correct tool is a 18MM deep socket with the side cut open to allow a slot for the electric wire. I was able to reinstall with a 18MM "crows foot". I would highly recommend replacing the coolant sensor when replacing the thermostat, due to the amount os time it takes to get to either of theses compodents.



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All lights go blank after gmc envoy 2002 warms up. why?

There may be a bad wire somewhere. I would check first the the thermostat and its wiring for exposed conductor or bad insulation or wires in contact with metal or other wires. The thermostat is located at one of the radiator hoses. It looks like a plug from the outside and has wires connected to it.

Nov 01, 2012 | GMC Cars & Trucks

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Check this...
  1. Remove the air inlet duct.
  2. Drain the cooling system.
  3. Remove the radiator outlet hose.
  4. Remove the thermostat housing bolts.
  5. Remove the thermostat from the water pump housing.
NOTE The O-ring seal is integral to the thermostat housing


Fig. Thermostat housing - 4.8L, 5.3L and 6.0L engines (clikc image for zoom)

Hope helps (remember to rate this answer).

Dec 10, 2010 | 2002 GMC Sierra

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Need steps on replacing thermostat on 2002 Envoy

Just replaced my 2005 envoy thermostat, and it might be the same. Here is what I had to do.
1. First, the thermostat was located on the driver side behind the alternator. The hose comes from the bottom of the radiator, not the top like most vehicles I have worked on.
2. You need to remove the belt by taking tension off of it. The tensioner is on the passenger side, under the steering pump. I used a socket wrench, placed in in the square hole on the tensioner, attached a pipe for leverage to the socket, and pulled until the belt was loose.
3. Next is removing the alternator. Best if you first disconnect your battery, as there is a hot line to the alternator. Disconnect the wiring harness located on the top. Remove the bracket bolts that hold the alternator. You might want to place something under the alternator to prevent it from damaging the small wheel under it as it will be heavy and free after you remove the bolts. I also removed the bracket to get full access to the hose and thermostat. There is a red wire that connects to the alternator, remove it and now the alternator can be pulled out and set to the side.
4. Once all this is out of the way, you can remove the hose to the thermostat (I assume you have drained the radiator).
5. Remove the two bolts hold the thermostat to the engine.
6 Replace the thermostat and reverse the order of the steps above.

I read that some can do this without removing the alternator or just loosening, but it is tight and makes the job a lot harder.

Hope this helps...Joe

Mar 06, 2010 | 2002 GMC Envoy

2 Answers

How do I remove the thermostat from the 2004 GMC Envoy????

It's actually very simple. Follow the upper radiator hose to the top of the engine block. You will see a housing which the hose is attached to. Remove the hose from the housing. The housing will have 2 or 3 bolts holding it down. Remove the bolts and lift the housing off. The thermostat will be sitting there and you simply need to remove it.

Dec 31, 2009 | 2003 GMC Envoy

2 Answers

2004 gmc envoy code 0128

This an engine coolant temperature fault, most likely caused by a defective thermostat, probably one that is open all the time.

Jul 17, 2009 | 2002 GMC Envoy XL

1 Answer


its behind and below the alternator follow the top radiator hose down to it.the alternator has to come off.then you will see t-stat housing the t-stat is built in the housing so your part store should have this housing and stat together.there are two 10mm bolts that hold on housing the bottom one is hard to see.most shops will do this job for about$ 200 .

Jan 29, 2009 | 2003 GMC Envoy

5 Answers

Check engine light on - 2003 gmc envoy XL

That code represents a lower than expected reading for temperature (coolant). First thing to do is check your coolant level, as if it is low, then the sensor can not read correctly. Second, you may have a thermostat that is stuck open, allowing the coolant to cool off too much. The sensor should be mounted on top of the engine, near the thermostat housing.

May 18, 2008 | GMC 2003 Envoy XL

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