GM 3.1L V6 (THERMOSTAT)

[SFCP]

Anyone know where the thermostat on this engine is located?
My temp gague inside the car reads between 100 to 220, and
the temp needle always rides on 130'ish to 140. This seems a little cool to me. I remember the needle typically reading closer to the middle around 150-155. Would I be correct in assuming this is a bit cool to register? The heat seems good inside the car, but I'm guessing it could get a little hotter if the stat were functioning properly.
This is on a 1995 Chev Lumina with 131k

 

[CBDFrontier06]

It might be safe to assume a lazy guage versus a bad thermostat, especially if you're still getting good performance from the heater. My roommate's Explorer rarely read very far above "C" on the highway in 100 degree heat in Texas...that was obviously wrong, and yours may be too. His thermostat actually failed later, which seemed to light a fire under his temp guage, but after I replaced it with a genuine Ford unit, the temp guage went back to reading low.

 

[SFCP]

Hmmm...well, I called my mechanic on it as well, he wants me to bring it by so he can take a temp reading on the heater. I guess he can tell that way if the stat is functioning well or not.

 

[Chris142]

It's in the tube behind the exhaust crossover! Big PITA to access.

 

[SFCP]

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It's in the tube behind the exhaust crossover! Big PITA to access.

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That's just great!

$5.00 part, $200.00 repair

 

[benjamming]

I replaced the thermostat on my '94 Grand AM 3.1L V6 in just a few minutes. It wasn't a problem at all. It's on the passenger side.

 

[PF52]

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I replaced the thermostat on my '94 Grand AM 3.1L V6 in just a few minutes. It wasn't a problem at all. It's on the passenger side.

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Passenger's side? Hmmm, I've never seen that configuration.

 

[Drew99GT]

Follow the upper rad hose from the rad back to the engine. That's where the stat is, on the Driver side of the engine; it mounts into a housing on the lower intake manifold. You can get at it fine if you have some u joint extensions for your sockets; the front bank exhaust crossover is painfully in the way like Chris142 indicated.

With some scraped knuckles, enough swear words to warrant some forgiveness from the almighty, and a beer or six, it ain't no biggie.

One good way to find out if it's really sticking open, is to fire the motor cold, or better yet, refire after it has been run and cooled off, let it idle with the hood open, and keep your hand on the upper rad hose. It should feel cool, then all of a sudden, it should feel very hot when the stat opens. Also keep monitoring the temp gauge. If it never seems to get scolding hot all of a sudden, then the stat is likely stuck open.

 

[SFCP]

getting replaced this Friday... the heat in the car does not get as hot as it once did. I know for certain it is getting stuck up, plus it's orginal with 130k on the engine.

 

[Drew99GT]

No heat is definitely another indicator of a stuck open stat, and running the heater full blast further cools the engine and contributes to the lack of heat.

 

[alreadygone]

Believe it is behind crossover as stated. Tough, but doable long as you have a warm shop and a COLD engine. "Gear Wrench" brand box end wrench also helps. If you don't have "Gear Wrench" brand (available at Lowes among others) this might be the perfect excuse to purchase.

Bob

 

[alreadygone]

Main tool necessary,,,PATIENCE !! Believe I'd also leave the suds alone till job complete!

Bob

 

[Pluto5]

You are making an unwarranted assumption about the temperature since the gauge is not graduated, i.e., it only shows the highest and lowest values and you cannot correctly determine the actual temp. Good luck on replacing it if you don't have very small fingers....

 

[Drew99GT]

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it only shows the highest and lowest values and you cannot correctly determine the actual temp.

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Not on these GMs, they are accurate. Not idiot gauges like they put in a lot of Fords.

 

[SFCP]

Well, for one thing, I'm very intune to what my vehicle is doing. I drive much of the time with no radio on so I can listen to the car run, and listen for abnormalities. Also, I ALWAYS pay attention to my gagues because many people don't and run the risk of burning up an engine if something happens and they are only looking down the road. I always remember this Chevy Lumina of mine running just about in the middle, and now the heat gague BARELY takes off and when it does, it only hovers between halway and the middle. That gague is deffinatley getting stuck open, and I'm dumping it for a new one on Friday. Found out it will only cost me 145.00 to have my mechanice do since I don't have the time to mess with it.

 

[PF52]

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No heat is definitely another indicator of a stuck open stat, and running the heater full blast further cools the engine and contributes to the lack of heat.

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I went through this issue some years ago with my Beretta. Thermostat was stuck open but heat was decent in town. However, there was NO heat at highway speeds! Wintertime on the highway was bitter cold once the sun went down and I had to rely on the non-existant heater. Needless to say a new thermostat brought back my heat and probably saved me from frostbite. By the way, that engine was the 3.1 MPFI version, where the thermostat was mounted right up top and was literally a 5 minute job to replace. The 94+ SFI engines have it buried down below the crossover like the other guys have mentioned.

 

[Harvey]

I recently had the same prob with a 95 pont. 3.1, changed the thermostat and temp gauge still read the same, had to change the temp sensor to get the right reading.

 

[benjamming]

Thanks for the correction. I must have been thinking about a previous car, oh heck, I must not have been thinking! I went and checked at lunch and sure enough, it's just like y'all said.