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Since you said the fans aren’t coming on, it sounds to me like the ECT has gone bad, more-so than a thermostat. Since the two parts are right next to each other, IIRC, replacing them both wouldn’t be a bad idea. There’s only one way I know of to test an ECT sensor, and it requires a scan tool that has a data-stream display feature. Set the scanner to display engine temperature while the radiator cap is off and a thermometer is sitting in the coolant, preferably without touching the metal of the radiator. If the thermometer is within a couple of degrees of the shown temperature, then the sensor is probably fine. I’m guessing that there will be a large disparity between the two though. One other thing that occurs to me is this: air is a poor conductor of temperature compared to liquid, so just because the gauge doesn’t show an overheat condition, if the coolant isn’t reaching the sensor, it’s just guessing.
Also, I’d try to figure out where the coolant is leaking from. Coolant doesn’t evaporate very fast, especially in the winter time, so it’s got to be going somewhere. Fix the leak, put a fresh thermostat/gasket on it, replacing the radiator cap isn’t a bad idea either if it hasn’t been replaced in a while and see if that fixes it.
First off, it would be really nice if you did not use caps for your posts as it feels like your shouting. C8-)
A concern right away is the coolant loss. Also it sounds like there is no circulation either.
Is there any CEL? And do you have access to a scan tool that can show live engine data?
Here is a video Eric made on solving over heat issues –
http://www.youtube.com/user/EricTheCarG … UzOTnsWImI
I would watch the above video and then report back to us.
I also forgot to add that ECT can also be easily tested without a scan tool but you do need a DVOM.
Depending on the ECT sensor type (PCT or NCT type), the resistance of the sensor will increase or decrease as the temperature of the coolant increases. But you will need to locate a chart that will show the engine coolant temperature for a specific ohm reading value.
Quoted From dreamer2355:
I also forgot to add that ECT can also be easily tested without a scan tool but you do need a DVOM.
Depending on the ECT sensor type (PCT or NCT type), the resistance of the sensor will increase or decrease as the temperature of the coolant increases. But you will need to locate a chart that will show the engine coolant temperature for a specific ohm reading value.
We did the same tests in class back probing the sensors and watching the voltage drop. It would range between ~1v to around ~5v. I honestly forget which way they normally go, but as the car warms up, the voltage should climb or fall at an even rate. It’s a very easy test. If you want more info on it, let us know. We never checked ’em by resistance as you said dreamer, but it’s the same principle.
It sounds like a stuck closed thermostat. .the heater hoses got hotter than normal because with flow was blocked back to the radiator (stuck thermostat)
the heater core was acting as the radiator. as for where the coolant loss went..if the engine was getting an over heat condition and your gage did not
register you may have been over heating into your over flow bottle for a while losing coolant that way.as for the gage not registering as stated above I
would check the coolant temp sensor.sounds like the sensor has a problem.I don’t know if the coolant temp sensor on your vehicle works the temp
gage and the fans or if the fans are separate? I would start with thermostat replacement, new radiator cap and new coolant. also check to see if the
coolant temp sensor does double duty or are separate sensors good luck and keep us posted.got a second cup of coffee mind is turned on again. as for the fans not coming on for over heat. find the relay for cooling fan circuit. pull it out. off your
battery hook up jumpers to coil side of the relay and listen for a click or hold it in your hand. with a meter set to ohms place the probes on the designated
terminals and see if the circuit makes and breaks.remove one coil coil jumper and to then reapply power to simulate the coil to energize and de energize.
that will tell you if relay is good.next jumper the socket pinned connections with fused jumper. see if fan turns on if it does that eliminates power to the fan.
this will tell you if the relay is a problem or power issue or both.you will also need to check coil voltage to the coil of the relay.Going back to the cooling fan issues, once the OP has figured out why his vehicle is over heating, i would first start off by checking the basics such as fuses for the cooing fan motors.
If a relay is suspect, he could also use another relay from the same fuse distribution box and see if the cooling fans activate.
Most vehicles will throw a CEL if there is an issue with the ECT or cooling system fans.
It would also be nice to see a wiring diagram and see how the PCM controls the cooling fan motors. From that diagram, we can also see exactly the safest method for using a fused jumper wire to bypass the relays.
A DVOM would be very valuable here.
I don’t think it’s the thermostat or the fan switch sensor but if you decide to replace the thermostat it replace it with an OE unit as they are much better than the aftermarket ones. The #1 cause of that issue is air in the cooling system and in the link that dreamer posted it mentions this very thing and if you had a ‘leak’ this is most certainly the most probable cause of that issue, here is a video on bleeding out the system, keep in mind you DON’T need the bleeder valve as it’s only there to help you fill the system faster do everything else in the video and you’ll be able to successfully bleed the air out.
http://www.youtube.com/watch?v=zUpXgAJ1 … ure=relmfuthe cooling fan never came on causing the over heat condition.the coolant boiled out causing low coolant. I don’t believe that the thermostat is the problem.
you need to check the fan circuit and coolant temp sensor. I retract my previous post on the stuck closed thermostat.Quoted From college man:
the cooling fan never came on causing the over heat condition.the coolant boiled out causing low coolant. I don’t believe that the thermostat is the problem.
you need to check the fan circuit and coolant temp sensor. I retract my previous post on the stuck closed thermostat.Actually I believe it’s the low coolant that causes air to be introduced in the cooling system causing all kinds of issues including overheat and lack of cooling fan operation, when confronted with an overheat situation the first step is always to verify if you have air trapped in the system and then begin your diagnosis. If you do find air in the system the next step would be to look for leaks by pressure testing the system, if you don’t find air in the system the next step is to verify cooling fan operation and airflow through the radiator these steps are outlined in this video.
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