Question : '95 Lumina 3.1 Coolant Temp High

[brianl]

I have a '95 Lumina with a 3.1 and want to know if there is one temperature sensor or two. I have the issue where the gauge gets too close to being overheated before the fan kicks in. The car is fine until a hot day in stop and go traffic and then the gauge goes too close to overheating. I replaced the temp sensor on the front of the engine that is easy to see from the front of the car and had no change in the symptoms. I have seen another part listed on gmpartsdirect.com that says it is a temp sensor but not the same thing that I replaced. Is the one on the front of the engine responsible for sending the temp signal to the gauge and the ECM? The thermostat is good, the fan relays are good. Is this an ECM issue where they are just supposed to get real hot before the fans kick in? I am considering getting a kit from JEGS made by Painless Performance that has a thermostat that runs a seperate relay that will turn the fan on at 200 and turn it off at 180. I was going to put the sensor in the where the coolant drain plug is in the front of the engine. I was going to hook this up only on fan #1.

[bszopi]

I don't know the exact temp off the top of my head, but the first fan probably doesn't kick on until between 210-220F. As far as temp sensors go, did the one you replace have 2 or 3 wires going to it? If it had 3, then that is the only temp sensor and it provides a signal to the dash as well as the ECM. If it only had 2, then there is an additional temp sensor in the rear head. It is a single (green) wire and provides the signal to the dash.

[robertisaar]

its a 95, so it should have 2. thats the way my monte is set up(also a 95 with 3100)

[brianl]

The temp sensor I installed had two connectors on it.

[robertisaar]

do you have a laptop or one that you could borrow? if so get an ALDL cable, download tunerpro RT and then we can determine if your sensor is bad or if your guage is inaccurate(likely) i spent $60 on my cable and not only is it stupid easy to use it looks nice, if you want to go the cheap route you could build one yourself

[brianl]

The cable sounds like something I will look into. I think the car is really getting hot though. Some oil residue starts to smell when the gauge is getting near the right so I believe it is too hot. If the sensor with the two terminals is the one that drives the ECM, then I already replace the one that makes the cooling fans cut in. Maybe the ECM is not telling the fan relay to kick in until too late. Everything else about this car runs fine, so I am thinking of running a seperate cooling circuit for cooling fan #1. On a lot of newer cars I hear the cooling fan cut in a lot sooner than it does on these cars. Maybe that is why so many of these have gasket issues and coolant leaks. If I get the fan to kick in at 200 degrees do you think that will lengthen the life of the LIM and head gaskets?

[robertisaar]

techniclly, as long as the whole motor is kept at a constant temperature wether it be 100* or 220*, it should lengthen the life of the gaskets(iron block plus aluminum top half, expands at different rates)

but don't go off buying stuff yet... something bszopi tried to do a while ago, and i am attempting now, is to convert the car back to obd1(most gm vehicles from 94-95, including your lumina, are obd1.5, untunable) using a PCM from a 91-93 cutlass supreme/grand prix/lumina with a 3.4, allowing you to tune it. the incentive for you is that you can change the temperatures at which the fans turn on and off. and that aldl cable will be useful then too, because should you want it tuned, or if you want to see why a check engine light is on(no handheld reader will work with the exception of the tech 2( and maybe the tech 1) but they are expensive, trust me), you'll be able to. if you want to tune it yourself, you'll need some other stuff, but i can burn a chip that'll turn the fans on/off to whatever you want. i'll even be nice and if thats the only thing you want done, just pay for shipping.

[talon2swords]

My temp gauge on my 97 Lumina would creep up during the summer. I was worried so I replaced the temp. sensor. It was still creeping up so I took it to dealership. They said it was supposed to do this, that tthe mechanic there owned one and it would do it on his.

I don't know if that is true, but one day I drove it home, waited for it to creep up and the fans did eventually come on before the red mark,so as long at they do come on, I'm not worried about it.

Also you could leave the AC on when it's a hot day, because the fans stay on when it is on (at least on mine).

Make sure the coolant system doesn't have air in it.

[Juglenaut]

If is indeed overheating you will not know really unless you get a laser temp gun on it, some parts stores can do this.

If you have 2 wire you have 2 sensors and this ECM is obd1.5 if the ecme was 2.0 then it will have 3 wires.

purging the coolant system is more important and later gens.

The water pump is easy to get too which is a plus. Also do you know when the last time the radiator was flushed??

[fastback4]

I purged my 1997 3100 and no more high temp gauge readings........