Temp Sensor Shot? Wierd problem

[b1aze]

This just recently started happening. I noticed one day that my oil temp gauge was reading a little low, and i didnt think anything of it, as I have my front grill out (the brackets broke so it was rattling like crazy, but thats a different issue) and i figured that the radiator was just getting better airflow thus running the oil a little cooler. That happened for a few days, then it started to affect the water temp gauge too, that was running cool. Now the water temp gauge doesnt go past 1/4 of the gauge and the oil temp barely breaks the very bottom of the gauge. My "Check engine" light also just came on but i have yet to have a chance to have that looked at.


Does it sound like the temperature sensor? Or is it something else? The oil pressure is fine and normal, but the temperature of the engine seems to stay "cold."

Thanks for any help!

[SoCal94]

Maybe your thermostat is stuck open? Or somebody took it out altogether?

SoCal94

[b1aze]

Why would someone take the thermostat out? It started randomly happening, and its been happening for about a month now. I might just get someone to tell me what tripped the engine light and go from there.

Is it terrible if the thermostat is stuck open? will it do any damage?

[SoCal94]

Well, if it's cold out the car would run really cool all the time, which isn't particularly good for it.

People do all sorts of strange things. For cars that chronically overheat, lots of folks think that removing the thermostat altogether would 'help'. In some cases it might seem to, but it's not the 'right' solution. (Finding out why it overheats and fixing that problem would be better). Are you the original owner?

And yes, if you have the Check Engine light on ... go to AutoZone or find a friend and have the codes read. AutoZone does it for free in most states.

SoCal94

[b1aze]

It has been 90+ the past few days and its been running cold. I am the 2nd owner and have put 15k miles on it or so and have owned it for the past year. Ill try to find an autozone to see if the thermostat is the reason it kicked.

Is it a fairly easy install? Costly?

[46 Cobra]

Sounds like a stuck thermostat which is a very bad thing.

To appreciate what is going on you need to consider that with fuel injection the computer compares the outside ambient air temperature and engine coolant temperature among other inputs to adjust the fuel mixture. As a cold engine requires more fuel to run properly the computer dumps extra fuel into the engine until the engine coolant reaches operating temperature. Until that temperature is reached some of the extra fuel does not get burned and that which is not expelled with the exhaust enters the crankcase. This is all very bad as a combination of oil and gas does not lubricate well, the cats are getting very very hot from burning the excess fuel and the vehicle MPG is terrible.

A new thermostat and gasket is less than $5 and it takes under 30 minutes to install.

[b1aze]

A decently easy self install?

Also, the Check Engine light turned itself off this morning, but the thermostat was up to normal at one point, then dropped again. I will be pricing out the parts and such asap.

Have any guidelines or directions to changing the thermostat?

[WD40]

Have you had any diagnostics (pull codes) done lately??
^^^That should be your first step.

BTW, a "tired" charging system will also cause funky gauge readings.
^^^It wouldn't be the first time your very same symptoms showed up,
and it turned out to be the alternator, or something as simple as a bad ground wire.
I'd certainly get the codes pulled first before tearing into anything at the moment.

If it is indeed the thermostat...
http://www.focushacks.com/index.php?modid=59

[b1aze]

No lately. Ill try to drop it off sometime this week just to get it looked at. Will the codes still show up even though the light is off?

[SoCal94]

Possibly, if the computer stored a 'freeze data event'. That can be viewed with the code reader.

Otherwise, they'll find no codes.

If something causes the light to turn on, but then that same thing doesn't happen for many cycles of the ignition key, the light will go off. I forget if it's 20 or 50 or what.

SoCal94

[b1aze]

Just went to Auto Zone and they checked the code as:

"Coolant temp sensor"

So im assuming that is whats throwing this whole thing out of whack.

Any good ideas? Thanks so much for all of the replys so far! Muc MUCH MUCH appreciated

[SVTfocusO3]

Usually is has some more to it, im guessing it was maybe a PO115 - PO119 or a P1116 or P1117, this would help.

What you could do is pull that sensor and ohm it out with a DVOM(digital volt ohm meter), it shoud be an NTC thermistor, so it will change resistance with temperture changes. Resistance will go down, when temperture goes up. So somehow get the specs. of what it should be, or just see if it changes when you breath on it or heat it up with something.

If your lost, Autozone has them for $30.99 or so, and just replace it, BUT thats not what you should do.

[b1aze]

Is it just a plug-and-play install?

[SVTfocusO3]

Pretty much, shouldn't be too hard. I believe it's right there on top of the thermostat housing, but you should make sure that's the problem. Diagnosis is key!!!

Make sure you have enough coolant as well!!!

[b1aze]

It ended up being the thermostat itself. It was stuck open. I figured it was the thermostat sticking because the temp would occasionally float up when i came to a stop. All is working and in good order.

Thanks all for your help!