Lumina running hot at idle

[rocketman]

We have a 1997 Lumina 3.1 L - 76,000 km that runs extremely well. Lately I've noticed that the cooling fan isn't coming on at idle after driving for a while and the temp gauge slowly increases. Makes me nervous with the family in the car on a highway during a traffic jam. I did notice though this weekend the fan will kick on if I turn on the A/C while idling at high temps. Why won't it kick on without turning on the A/C ? The gauge climbs to more than halfway, almost to 3/4, approaching the Red "danger zone"

 

[drivewaytech]

You should have two fans on your radiator. One fan is a condensor fan that is wired to turn on with the a/c only. The first fan may have a bad motor. One way I test the fan motor is to cut the wires going to the fan motor and splice in wires that are long enough to reach your battery. Touch one wire to the positive terminal and one to the negative terminal. If the fan does not start running, you've got a burned out fan motor. You can buy aftermarket "near fits" at the parts store for around $50. If the fan does kick on with this test, then you got a bad thermal switch or problem elsewhere in the wiring system. These fans are not that dificult to replace. Make sure you tie-up/tape the other end of the wires you cut so they don't get caught in something and are easy to find come time for repair.

 

[chas3]

turning on the a/c usually turns on the fan to pull air across the a/c condenser. if you have a two speed fan setup, its usually low speed.

as for your original problem, it might be a bad sensor. the temp gauge is usually on its own sensor, independent of the sensor the computer uses to decide if it needs to turn on the fans. its not clear either that the gauge is right either. you need to hook your engine up to a scanner see what's what.

 

[mstrjon32]

IIRC, the '97 Lumina has only one temperature sensor, and the PCM and the dash gauge share the value (Luminas up to and including '95 has two sensors). Also, turning on the A/C should kick on both fans, regardless of engine temperature, so turn on the A/C and watch for both fans to start. The fan on the passenger side will only start (I think) for the A/C. It may also start if the car starts to excessively overheat, I don't remember exactly.

I would check to see if both fans work first, simply by setting the A/C to max and seeing if both fans start. If the fan on the driver's side doesn't start, either the fan is bad or you've got a wiring/relay problem. If you're seeing a temperature reading on the dash, then the PCM should also be getting a proper temperature reading.

Whatever you do, don't let that 3.1L overheat! I love the GM 60*V6 design, but it does not take well to overheating. They will very quickly warp one or both heads, and you'll be up the creek.

If you still can't get it sorted out, let me know and I can dig out my '97 W-car service manual.

 

[Matt_S]

With all due respect, I think the first two posters are way off the mark. The first things you should be looking at are the fan relays. There should be a low and a high speed fan relay in the fuse box (the owner's manual should show their location). When the computer decides to turn the fan on, it'll activate one of those depending on the conditions. I'm betting that one of those relays is bad. To test, let the car warm up a little and turn on the AC. Both fans should come on at low speed. If they do, your wiring and fan motors are fine (good news). Shut the car down and switch the low and high-speed relays (they're the same part). If the fans don't turn back on when you start it back up (AC still on), you've found the problem. Any auto parts store should carry such a part.

 

[rocketman]

Thanks to all. Yes, both fans come on when the A/C is turned on, so I guess that's good news (both fans work). I will check out a few of the things that were suggested, doesn't sound too difficult.

 

[Drew99GT]

The fans on these vehicles are programmed to turn on low at I believe 215 and high at 230. If it's running hot on the gauge, the low speed fan setting should at least be running. Check that first, and they will always run low speed when the A/C is on and will kick to high speed when the pressure in the A/C system gets to a certain point.

I hate it; my mom's Olds runs the exact same way, get really hot in stop and go, but if you turn the A/C on, it cools right down cause the fans stay on all the time.

 

[wiswind]

I am sold on having the A/C ON in hot, stop and go traffic for just this reason.
The fans STAY on, an this results in the engine staying at a more constant temperature.....even more important, the transmission will be better cooled.

It is good that the fans both work, now you just need to narrow it down to the temperature sensor activation part.....maybe a internet search on "lumina radiator fan" will help you.
Lots of Luminas out there, so I'm sure that there is a lot of data for you.
Focus on year(s) close to your year.

 

[mstrjon32]

I'm not too worried about the engine running slightly above normal in traffic, honestly. IMO, you're reducing wear by running the engine slightly hotter at idle and additionally saving gas. If it bothers you, you can always wire up your own relays which can trigger the fans via a switch.