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-   -   Car overheating (http://www.focusfanatics.com/forum/showthread.php?t=312456)

leemanfor 03-22-2013 01:39 PM

Car overheating
 
Hello all

I haven't really ever had any issues with my wifes 2011 Ford Focus! its a great car and much more comfortable than mine haha.

Anyway, we were driving last night on the freeway and all of the sudden the temp gauge on the car went to H and the temp light came on saying its overheating. I panic and pull over and shut the car off immediately. Mind you the temp outside was 30 degrees.

I get out, check the car. No coolant loss...i got under the car and there was no wet leaks anywhere...the overflow tank is completely full and not really hot. no boiling water. Basically no sign that the car was actually over heating.

I get back in, and start it up and the temp reads normal. Now my thought is possibly a bad thermostat but the car has 42k miles and this is the first time this has happened.

Any thoughts?

Thanks!

bile0026 03-22-2013 02:38 PM

Maybe an air bubble in the system. IIRC the coolant temp sensor is a "hydro sensor" meaning it will only read liquid temps not air temps. If an air pocket gets stuck around the sensor it won't be able to read the temp and I believe that it will cause it to read Hot (not 100% sure). The car can also overheat if there is an air pocket that is causing the coolant not to circulate. I would get the coolant flushed or "burp" it with one of these (a lot less messy with one of these). Its somewhere to start anyways.
http://i1167.photobucket.com/albums/...oolantburp.png

If there is an air bubble you may want to check for a pinhole leak in one of the coolant hoses or check for a weak clamp that may be allowing air into the system. Otherwise you might end up back in the same boat.

leemanfor 03-22-2013 02:42 PM

Quote:

Originally Posted by bile0026 (Post 4649066)
Maybe an air bubble in the system. IIRC the coolant temp sensor is a "hydro sensor" meaning it will only read liquid temps not air temps. If an air pocket gets stuck around the sensor it won't be able to read the temp and I believe that it will cause it to read Hot (not 100% sure). The car can also overheat if there is an air pocket that is causing the coolant not to circulate. I would get the coolant flushed or "burp" it with one of these (a lot less messy with one of these). Its somewhere to start anyways.
http://i1167.photobucket.com/albums/...oolantburp.png

If there is an air bubble you may want to check for a pinhole leak in one of the coolant hoses or check for a weak clamp that may be allowing air into the system. Otherwise you might end up back in the same boat.

That makes sense. It would read hot air and not hot temp, so therefor going all the way to H.

bile0026 03-22-2013 02:49 PM

Not quite. The way the sensor is designed it won't read air at all which I think makes it jump to H so that if there was no coolant in the radiator you would know. Liquid temp sensors only work in liquid, they can't read air temps.

FordService 03-22-2013 02:52 PM

Quote:

Originally Posted by leemanfor (Post 4648988)
Hello all

I haven't really ever had any issues with my wifes 2011 Ford Focus! its a great car and much more comfortable than mine haha.

Anyway, we were driving last night on the freeway and all of the sudden the temp gauge on the car went to H and the temp light came on saying its overheating. I panic and pull over and shut the car off immediately. Mind you the temp outside was 30 degrees.

I get out, check the car. No coolant loss...i got under the car and there was no wet leaks anywhere...the overflow tank is completely full and not really hot. no boiling water. Basically no sign that the car was actually over heating.

I get back in, and start it up and the temp reads normal. Now my thought is possibly a bad thermostat but the car has 42k miles and this is the first time this has happened...

Hi leemanfor,

I recommend making an appointment at your dealership so they can take a look. They'll be your best bet for getting an accurate, prompt diagnosis. Keep us posted on how things progress; if you need my assistance, I'll be here!

Crystal

leemanfor 03-22-2013 03:18 PM

Quote:

Originally Posted by FordCustomerService (Post 4649095)
Hi leemanfor,

I recommend making an appointment at your dealership so they can take a look. They'll be your best bet for getting an accurate, prompt diagnosis. Keep us posted on how things progress; if you need my assistance, I'll be here!

Crystal

Thanks Crystal

leemanfor 03-22-2013 03:19 PM

Quote:

Originally Posted by bile0026 (Post 4649083)
Not quite. The way the sensor is designed it won't read air at all which I think makes it jump to H so that if there was no coolant in the radiator you would know. Liquid temp sensors only work in liquid, they can't read air temps.

ok. I think i need to see if there is a bubble in there like you said.

amc49 03-22-2013 10:04 PM

Having trouble with some of this. Every water covered sensor I've ever seen for 50 years will not read if no water around the sensor. It shows low not high. Think it out, air does not conduct temp like fluid does. The sensor itself has no way of knowing whether it is covered with fluid and can only reflect temp around it, again, if air then no temp since air carries temperature much slower because not as dense as water. Also, cooling systems are under pressure, they cannot suck air except under very rare and specialized circumstances. I haven't seen a car EVER suck air and have worked on hundreds. Even a pinhole leak will spit fluid rather than suck air, only way to suck air is to be out of coolant anyway, once pump hits the airpocket it ceases to suck. meaning you have to lose much coolant before you can ever suck air. These systems are set up to quickly and fully bleed air into reservoir tanks all the time and keep it there only so you can see it, something is wrong if it is not doing that. I have two Focus and NEVER bleed the cooling systems, they are already done by the time the stat first opens.

leemanfor 03-23-2013 12:20 AM

Well see thats what I dont understand...the car was not overheating. Ive overheated a couple cars and steam blows out and usually the overflow tank is boiling.

nothing even seemed remotely out of place. The motor wasn't extremely hot, the overflow tank was full and at "Hot" on the meter and the radiator wasn't even hot. maybe it was just a sensor issue, cause the car runs fine since

mikebontoft 03-23-2013 12:35 AM

Gauges lie. That's all I can say. Keep an eye on it though. You may end up having a faulty sensor.

What is this talk of sensors "not reading?" A thermistor is a thermistor, with the exception of having a positive or negative coefficient. GM has used the same sensor for both coolant temp and intake temp on MANY vehicles.


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