Hey Guys, I posted this in the newbie section, but figure I may get more responses here. The High Engine Coolant Temperature/Automatic Transaxle Fluid Temperature and Low Coolant Level Warning Lights come on in my son's car after about ten minutes of driving. The fluid looks and smells good, but I'm going to change it and the filter tomorrow. There is anti freeze in the over flow jug, so I'm guessing the radiator is okay. I may go ahead and do a flush and fill on it too. What say you guys that know these cars? Could it be a faulty sensor? Thanks for suggestions.

 

low coolant level warning light, if, the coolant level isn't actually low, can be caused by the low coolant sensor in the bottom of the reservoir getting crudded up or actually just goin bad. If you do a flush n fill on the cooling system, give the reservoir a good cleaning.

IF THE CAR IS NOT TRULY OVERHEATING:

Would recommend a GM sourced brass-style replacement of the ECTS (and its connector) the two wire device mounted in the head that the PCM uses to monitor coolant temp. These sensors often go bad. I can't imagine the original resin tipped one is still in there but if it is then it is dead.

what does the temp indicator on the dash say when the high coolant light comes on?

 

I would look for a stuck/damaged/defective sensor on the overflow jug. They can get gummed up. You may have to take loose the tank, and violently agitate it in a partially filled condition to get the sensor to operate (shake the heck out of it). This is a simple on/off type of sensor switch, so you should be able to test the operation with an ohmmeter before reinstalling the tank. With that many miles on the car, and not knowing if/when it was last flushed, doing it now might save a world of headache in the future

 

Hey Derf, what is the ECTS? Is that electronic coolant temperature sensor? If so, where is it located? The temp gauge on the dash doesn't even quite make it up to the half way point and we've had heat in the upper 90's for seven straight weeks now. Thank you to you and OceanArcher for your quick replies. I'll definitely remove the over flow jug and give it a good cleaning and look at those sensors. I do have a DVM. Any idea what the resistance should read on the sensor? I agree with you, OceanArcher, about flushing and filling the system. Can I use the 50/50 mix off the shelf at Walmart or does this system need Dexcool or HOAT or something special?

 

Indeed - ECTS is a 2 wire device mounted in the head on the passenger side. Connector is a squeeze off so don't try to pry on it. Replace with GM sourced brass tip stlyle replacement and replace the connector too.

I forgot you have a 95 -- these have two coolant temp sensors - the one driving the dash is a single wire connector -- the one the PCM keys off of is the 2 wire sensor. So it is possible that the 2 wire one has failed and is reading way high. Leave the single wire one alone for now and replace the two wire ECTS.

50 50 prestone should be fine

 

Like Derf says ... if you're gonna do a flush and refill, the 50-50 will work just fine. As far as the ECTS and connector, the parts will prolly set you back about $40usd. Use Teflon tape on the threads when putting the new one back into the head. The sensor in the overflow tank is just a "snap switch", either open (no reading) or closed (short). Make sure the one in there will give both readings (turn the tank upside down)

 

Thanks guys. I may have to put this on hold for a few days. The heat and humidity are unbearable here right now for more than an hour or so. I spent an hour today clearing the headlights from the 16 years of neglect they've seen. I used one of the 3M headlight kits from Advance Auto Parts and am pretty well pleased with the results. They don't look like milk jugs anymore. That pretty much did me for the day, so I'll probably get up early tomorrow and do the over flow check and the sensors too. If it's too muggy, I'll just let it go for another couple of weeks. This 90 plus weather and high humidity is just too rough for an old dog like me to tolerate anymore. I've had two brain surgeries and my internal thermostat is messed up. If I get too hot, I have terrible headaches and it takes me over an hour to get cooled down.

 

Hey Guys, I got up early and removed the overflow jug on the coolant system. The antifreeze in it looked good and tested to -25, so I decided not to flush the system. I did clean out the jug real well and cleaned the senor on the bottom of it and the sensor in the head. I also changed the transmission fluid and filter and cleaned the sensor on the transmission. What ever I did, cured the light problem. I drove it for about twenty minutes and it shifts good and stays cool and the lights are off now. So thanks for the tips. I appreciate your help.