weird temp gauge issue

[chad keene]

Ok so this is the run down, my thermostat housing started leaking, so decided to replace it. Well before it was replaced even with it seeping, the vehicle never ran hot, so replaced the housing, the sensors, and thermostat, now it shows it's running hot, but here's the issue.



Immediately on startup even with the engine dead cold, and the vehicle setting for hours, on startup the temp gauge automatically rises to the middle within 10-20 seconds showing its already up to operating temp, which I don't see how that is even possible, and as you drive it, it gets up near the H mark, not in the red, but gets close to the H within only few minutes of driving maybe 5-10 minutes.



Well we have had the coolant system flushed, all new 50/50 mix, radiator coolant system checked for air, fan clutch checked, still same symptom. As I said before the swap we never had any trouble ever with it getting warm, could it be a faulty temperature sensor? How could the engine get up to operating temp so fast within 30 seconds or less? Would a stuck thermostat cause the temperature gauge to rise that quickly?

 

[Taylor Corn]

My thoughts are locked thermostat. Faulty temp reading. Air in thet system.

 

[chad keene]

Would a stuck thermostat cause the engine to heat up that fast though? I am thinking the new temperature sensor may be faulty or the incorrect one. I bought the whole assembly as a kit housing, sensors, thermostat , all new together.

 

[Taylor Corn]

Part numbers?

 

[Todd Z]

Maybe the sensors are in the wrong spot, wrong sensor, Pinched wire or the sender you installed is bad.



Todd Z

 

[fred fdunfordcomcastnet]

I'd suggest getting a scan tool that will read PIDs (aka DIDs). Then set it up to read ECT and with engine cold and off, start scan tool and begin reading the PID. With engine running, observe the PID and gauge.



If the PID gives a cold reading like 80 or 90 degrees and the gauge is showing hot, then you know that the gauge is wrong and you can begin tracking it down.



If the PID reading seems to correlate to the gauge, then you know you have a cooling issue and can start tracking that down.



I believe its Autozone that has a loaner scan tool that will pull PIDs so it shouldn't cost you anything to run this experiment.

 

[chad keene]

Thanks for the info and help. I didn't see any part numbers on the new sensors, I bought the whole assembly together the housing, sensors, thermostat as a unit. I made sure they were connected the right way same as before. I know there is 2 sensors, the gray one is the ECT for the PCM, and the brown one the Sender for the gauge. I know the original sensors were motorcraft but I didn't reuse those, maybe I should have.



Yeah I thought about running by autozone earlier, I also have a multimeter so I can use that as well.

 

[chad keene]

I tried the test, I turned the key to run but did not crank or start the engine, when the engine was dead cold from sitting overnight, and the gauge rose up right to the middle showing the engine was already up to operating temperature which is not possible, as it sit all night overnight. Then I disconnected the sensor connector turned the key to run again but did not crank over or start the engine, and the gauge sit right on the C mark.



Afterwards I decided to try the original sensor that was in it with the original housing and the gauge was normal again, so I am guessing I got a bad temperature sensor or the wrong one with the wrong resistance.

 

[fred fdunfordcomcastnet]

Yes, new housing must have the wrong TStat in it (or it's bad out of the box). It sounds like you can install the old TStat into the new housing so your all set, right?

 

[EddieS'04]

If it is a ford t-stat throw it away. I will anly use stant t-stats. If you compare the design. the ford is very restrictive ...JMHO

 

[Gavin Allan]

Here ya go!

 

[chad keene]

It was a bad temperature sensor, but as recommended I did replace the motorcraft with a stant thermostat also which looks to be built better. That's the one I got in the link.