OEM Thermostat Temperature

[Camdo]

What is the proper thermostat temperature for a 2005 GMC Envoy SLT with 4.2L engine.
Aftermarket offerings are 160, 180, 190 F. Which is correct? I cannot find where this is specified in the official manual, and the GM part description does not give its temperature rating.

 

[mrrsm]

Your Vehicle Profile does not display the Year Of Manufacture...but for the say...2006 and later Envoys...they employ the 192 Degree F Thermostat that will prompt the unit to open then and the Fan should engage around 210 Degrees F. The problem begs though that the system responds differently from the earlier designs, due to moving the Engine Temperature Sensor to the Far Rear Passenger Side of the LONG Aluminum Engine Head.

There may be some adjusted PCM Calibrations available for Update of the PCM if the Engine Coolant Temperature climbs above 212 Degrees F...ordinarily when Water Boils ...but only when unconfined at an Atmospheric Pressure of 14.7 PSI via Sea Level. Those conditions Do NOT prevail as long as the Engine-Head-Radiator System is soundly contained (Closed Circuit Coolant Cycle) with Good Hoses and a Tight Radiator Cap and when using the Correct 50/50 Mix of Distilled Water to Dex-Cool Coolant as a proper ratio.

The reason for tolerating such High Temperatures in the Coolant is because the *Stuff* gets routed from through the GM LL8 Atlas Vortec 4200 from the "The Top Down" in order to prevent the Aluminum Engine Head from Warping under conditions that are meant to improve Combustion Efficiency and mileage while using Lower Octane Fuels that perform best at around 210 Degrees F in a High Compression Motor (with a 10:1 or Better Compression Ratio)

 

[Chickenhawk]

Wow. I had to take a look at Rock Auto to confirm. I seriously cannot believe they even list 160 and 180 degree thermostats for our platforms! Good Lord, they do.

Listen to the advice above. ONLY get a 192-degree thermostat.

A 160 or 180 degree thermostat may seriously shorten the life of the cat converter as the PCM richens the mixture, thinking it is still in cold start mode. Certainly not as serious as one stuck open, but detrimental nonetheless.

After installation, a properly working thermostat should show a temperature gauge indication a tiny tick to the right of center. (The gauge is not linear, and even a slight bit to the left shows a defective thermostat or coolant temp sensor.)

 

[Camdo]

Thank you for all the replies.
My instrument cluster has temperature of 210 F in the 12:00 position.

I read in the manual page 6-605 "Thermostat Diagnosis" that the range of operation is between 188 and 206 F. That is the best information I can find that resembles a specification in the manual.

I am getting a P0128 code so will replace the thermostat and temperature sending unit. Water pump is slightly leaking so I will replace that too.

I am thinking of replacing the upper and lower radiator and heater hoses while I am in there, or am I overdoing it, as they are original but not failing at 247K miles. What do you think? Do hoses last forever in todays modern vehicles?

 

[mrrsm]

Yes... As long as you are being assisted by a Lisle Hose Clamp Tool like THIS One...Then... Changing them out will be very straightforward:

Amazon.com

 

[Redbeard]

I am thinking of replacing the upper and lower radiator and heater hoses while I am in there, or am I overdoing it, as they are original but not failing at 247K miles. What do you think? Do hoses last forever in todays modern vehicles?

I would strongly recommend changing out both the upper and lower radiator hoses especially since you are working on the cooling system. Along with flushing out all the old antifreeze. Turn the heat fully on to also get all the old antifreeze out of the heater core too. If you purchase antifreeze concentrate use distilled water to mix it 50/50 to get the correct concentration of antifreeze. Belts and hoses do last a little longer than years past, but preventive maintenance goes a long way when you are broke down away from home. Also take look at the fan belt. If there are any cracks at all change it also and you will have it off when changing the water pump.
just my 2¢
I do wonder what condition the antifreeze is in with the original hoses are still in place, because most antifreeze is not meant to last 19 years and the person flushing out the antifreeze probably would have changed out the hoses at the same time.

 

[Mooseman]

And since you have an 05, I would strongly suggest you also replace the temp sensor which is located right above the thermostat on the block. They do fail and since you are there, might as well do it. Cheap insurance.

 

[Chickenhawk]

Have you replaced the water pump before? Not an easy job, but with the help of this forum, I found ways to make it easier. I didn't remove the shroud and I used a short length of chain and a longer water pump bolt to hold it in place while I broke the nut loose. I ended up trying different tools for removing the water pump nut and nothing worked. (It had never been replaced before.) I finally ended up with an adjustable spud wrench, which is like an adjustable wrench but with a tapered handle. I then slipped a three-foot iron pipe on the handle, and it popped off easily.

 

[mrrsm]

Thank God for @Matt 's Epic Water Pump R&R Thread... :>)

How to replace the water pump

Total time, about an hour. On the OS someone claimed to have done it in 30 minutes, but it took me about an hour from getting everything out to having everything packed away. Make sure the engine is COMPLETELY cool before doing this. Best bet is to do it first thing in the morning. Remove the...

gmtnation.com

 

[Camdo]

Thanks guys. Ordered everything: pump, belt, hoses, 192 F thermostat, temp sensor and a cable hose clamp plier! Read @Matt 's article need a 35mm wrench and some chain. Having everything on hand is a real time saver.

 

[Mike534x]

If you don't have one, a 15MM flex-head ratcheting wrench makes life so much easier for removing the bottom alternator bolts.