Coolant temperature is zero [Archive] - Forum


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12-01-2009, 04:17 PM
Need help please.

After drove 40 miles this afternoon, the coolant temperature gage pointed to the far left (100). Turned on the heater and its hot. Stopped the car and kept engine running, both fans behind radiator were running. Stopped the engine and cheeked coolant tank, there were still 1 coolant there. Starting the car, the temperature gage moved to right and then fall back to 100. Is this bad?

12-01-2009, 05:22 PM
I believe there is a relay that sends the temperature reading to the gauge. I'm guessing that went bad. I couldn't tell you where it is or what it looks like, but if gauges fail it's usually due to a bad relay. Do a search and see if you can find anything. If not, I'm sure an electrical guru will reply shortly...

12-01-2009, 05:43 PM
Thanks for your help. Can I still drive the car?

12-01-2009, 05:53 PM
Not a good idea. If you're getting no reading on the gauge and it sweeps at startup (like its supposed to) that means more than likely your coolant temp sensor is shot. Your thermostat still works so if air is constantly flowing over the radiator you won't overheat too badly if you were forced to drive it. As it is though the computer has no idea what the coolant temp is and has to compensate in other ways it normally doesn't.

Do a search on ECT (engine coolant temp sensor) and see what pops up. If its someplace easy to access you could fix it yourself. In the meantime, make sure your coolant tank is at the full line and until you can replace the sensor (or have someone do it) don't drive the car on anything but "around the block" trips. Worst case if you do drive it, you overheat the engine and it seizes or starts on fire.

12-01-2009, 09:25 PM
I had to replace my ECT sensor earlier this year after I had the engine rebuilt. Turns out they used the wrong sensor so my readings were half of what they should have been.

The sensor itself is easy enough to replace but it's a messy job since you will spill coolant all over the engine if you don't drain it first. If you have a 3400 (V6), the sensor is located on the front driver's side corner of the engine itself just above the exhaust manifold (if my memory is correct.) It's brass colored and has a plug with a couple of wires coming off of it. The hardest part about getting it out is that there's very little room to get any tools in there without taking the throttle body off too. I did it in my driveway and just put a large plastic tub under the engine to catch all the coolant that spilled out.

I'd recommend taking the car to a mechanic unless you're a do-it-yourself'er with the time, patience and variety of tools needed to get it done.

12-02-2009, 08:04 AM
Thanks guys for the help. Here is what I have done:
1. did a search here on "ETC" and found I was not the only one had this problem.
2. went to Autozone had code scanned: P0128 plus SES.
3. checked low coolant, no problem; bought temp. sensor because was easy to do; ignored thermostat.
4. disconnected battery to reset computer, and wait.
5. this morning connected battery and gage started working again.
6. going to return the sensor and thinking about changing thermostat (original, 165K)
Conclusion: either onboard computer had Alzheimer or the GM guy programmed the computer had Alzheimer.

12-02-2009, 08:11 AM
If changing the thermostat, get a Failsafe, when they do go bad, they lock themselves in the "open" position, so coolant will still circulate through the block/radiator/heater core to keep over heating to a minimum.

12-02-2009, 10:56 AM
It's just a thermostat that needs to be replaced, I did this earlier in the year with the same symptoms, a couple of hours and it will be fine, look at the how to below , it helped me and the last few posts can suggest what you need and dont need to disassemble

12-02-2009, 11:28 AM
Great. I was just going to search this. Thanks.

12-02-2009, 12:53 PM
;1104252']If changing the thermostat, get a Failsafe, when they do go bad, they lock themselves in the "open" position, so coolant will still circulate through the block/radiator/heater core to keep over heating to a minimum.

I don't think I've ever hear of the FailSafe thermostats. I might have to look into them even though I hadn't put on my 180* one .. lol