For the past month or so, my temperature gauge hasn't worked, and I was told it may be the thermostat, so I looked up some information on it and decided to try replacing it.

While trying to get to the thermostat, I discovered a crack in the throttle body gasket, which I ended up replacing due to the car idling at 4000 RPM after I tried starting it when everything was put back together.

The good news is that my temperature gauge works again, but the bad news is that it goes up to quite near the red after idling for less than ten minutes.

Before now, I did drive the car about 5 miles, which I wouldn't have done if I wasn't going from one place to another. The gauge was all over the place on that drive, which sounds like it could have been due to the cooling system not being properly bled. I was able to bleed some more air out of it , but it was heating up so quickly that I didn't want to leave it running, so I'm unclear as to how much air may still be left in the system.

Another thing that I read may cause something like this was if the thermostat was put in upside down. I saw in many places that it was stressed that it wasn't up in backward, with the spring facing away from the engine, but I am wondering if this is a possibility.

Any input would be appreciated.

 

I believe your 3.1 is the same (or close enough) to the 3100 v6 in my '94 Grand Am. That being said, my assumptions are based of my Grand Am experiences.
The T-stat mounts vertically and is NOT possible to be put in facing the wrong direction.
I had an issue with my Grand Am where once per long trip (such as my 20 mile commute to work) my temp guage would spike (behaving like an air pocket was in the system). As I understand hot air cannot open a T-stat, you need hot coolant (it needs the fluid). I could pop the car in neutral and hold a slightly higher RPM (nothing crazy and no where near the rev limiter), release, back into gear and the temp began running fine. I also noticed when the temp guage would begin rising above normal operating temp, my heater was no longer blowing warm/hot air.
I kept bleeding out air from the system and got to a point I carried the ratchet and socket with me and would pull over to bleed air out. This went on for a while and no improvement.
About a week before I turned it over to a friend of mine (a professional GM mechanic), the car would idle rough from a cold start for a short time (such as until I reach the first stop sign or perhaps 1/8-1/4 mile). The biggest notable item was during that rough idle huge clouds of white smoke.

End result, i had a blown head gaskets. The air I kept bleeding off the coolant system was compression gases from the one or more cylinders. When I'd park the car and the cylinders no longer were compressing air, the coolant system bled off some pressure back into the leaking cylinders (with that pressure came coolant, and that coolant was the cause of the white smoke clouds). And the clouds I mention were HUGE (not little puffs of smoke).

Now, the point of me sharing all this is to see if ANY of these symtoms line up with your experience. I don't know enough to say it's a failed head gasket, but if you are able to keep getting air out of the system, eventually you need to reach a point where you have no more air to bleed. If not, you need to look into possible causes. Hopefully my experience gives some direction or other clues to spot for.

Now that I typed all this, I realised, I should just tell you to do the most logical thing first. Get a radiator pressure tester, pressurize the system and see if it holds. In my case, it did infact hold pressure. But if it does NOT hold pressure, find out where your leak is, it might account for the air you are bleeding off.

 

I believe that the 3.1 in the 95 is the 3100 engine, which seems to have been in quite a few GM vehicles, so I agree that it must be the very same.

Obviously, the possibility of a blown head gasket isn't what I wanted to hear, so I looked up some more information relating to that and I actually found at least two people that said blown head gaskets were "a common issue" with the 3100. I just figure anytime something happens to someone, they blame it on the product and not the way they treat it.

Not that any of that had anything to do with the issue at hand...

Following the aforementioned research, imagining the horror that must accompany replacing head gaskets, and bouncing the situation off of a few others, I may have come to a solution. I've thought that this air was coming out since I'd add coolant a bit at a time and the level would go down and I'd repeat until it seemed full again. Anyway, with the bleeder valve on the cooling system, I expected coolant to start coming out when there was no more air left, which I never saw happen. The importance of bleeding the cooling system and the way that the air pockets move became apparent when I ran the car for a while with the filler cap off. I walked away for a few minutes, and upon my return, I realized that a large air pocket had managed to escape through there, along with a good amount of coolant that ended up all over the inside of the engine bay and on the driveway. I guess it was important to go back again and learn that there are two bleeder valves and not just one.

It doesn't seem to be getting as hot while idling now and it doesn't seem to be happening as quickly, so that could be a good thing. The radiator hose on the right side, which I guess might be called the top hose or something, definitely didn't warm up as quickly as it has been, if at all. That might be a little bit concerning if there's something going on in the radiator, so I'm looking forward to seeing what the next problem will be with this wonderful adventure.

I appreciate your ideas on the situation, especially because thinking that it could be head gaskets caused me to try very hard to come up with anything else that it could have been.

 

I keep forgetting, when GM popped the 3100 into the N-Body, they made it "self bleeding". My Grand Am does not have a cap on the radiator. Instead, the overflow bottle serves two purposes (1, overflow and 2, it is pressurized and the cap on that bottle is the radiator cap). GM has a thin tube that allows air pockets to enter the top of the overflow bottle (once you have two much pressure, the cap will let the pressure/air out). So, the N-body is somewhat "idiot proof" (thus, it only has one air bleeder screw, which is really not needed, but it's there). That is a design I don't think GM passed out to the rest of cars they popped the 3100/3400 into.

My Grand Am had intake gaskets changed at 90K miles, then I did the head and intake gaskets in '09 at 180K. Being a "first timer" it took a while, but now I think I could do it in a weekend (perhaps even just a saturday). It's not to terrible to do. But then between friends and family, I have wrenched on about 5 different '94-'95 Grand Ams (and mine is one of two remaining, soon to be one). Treat that 3100 right and it will run for what seems forever (I have 205K on that '94 Grand Am and the drive train still runs great).