weird temp gauge issue

[just1me]

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?

 

[corkey]

thermostat upside down ?

 

[just1me]

Nope it is in there the right way, I've heard the radiator cap can also cause symptoms but Im not sure, it would describe this symptom.

 

[corkey]

i would take the temp sensor out, test it by heating it with a hair dryer, that will tell you in a hurry,, it it goes up way too fast, than it's the sensor,


does the rad hose and thermostat housing feel real hot ?? if only the therm housing is , and not the hose that tells you the therm is stuck,

 

[just1me]

I haven't felt the thermostat housing, but the upper radiator hose does get warm, but I wouldn't say really hot. Would a stuck thermostat cause the temperature gauge to rise that fast from a cold startup?

 

[bdmaash]

Wiring to the sensor, sensor itself, sensor wires swapped (there are 2 on there)


I think it's a thermistor (NTC) which gets smaller in value as it gets hotter, so maybe you got the wrong value sensor which makes it think it is hot.
It should take a few minutes to get to mid mark from a cold start,

Experiment: turn key to RUN position without starting with cold engine.
(mid mark is around 192 degrees farenheight, 212 degrees is water boiling point - varies with altitude)
- if needle rises still, unplug connector from sensor and observe needle position - it either should got to max temp or cold.

just a starting point to try and isolate problem.

 

[just1me]

Thank's I will try that tomorrow when I can see clearly, but I am thinking it's either the sensor or wiring as well, I will let you know.

 

[just1me]

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.

Wiring to the sensor, sensor itself, sensor wires swapped (there are 2 on there)


I think it's a thermistor (NTC) which gets smaller in value as it gets hotter, so maybe you got the wrong value sensor which makes it think it is hot.
It should take a few minutes to get to mid mark from a cold start,

Experiment: turn key to RUN position without starting with cold engine.
(mid mark is around 192 degrees farenheight, 212 degrees is water boiling point - varies with altitude)
- if needle rises still, unplug connector from sensor and observe needle position - it either should got to max temp or cold.

just a starting point to try and isolate problem.

 

[MidnightRebel07]

It might've been just the wrong sensor for that thermostat, did you replace the t-stat with the same temp spec one or a different temp spec? IIRC they sale on that's 195 degrees and one that's 180, if the sensor isn't for that spec t-stat than it would read wrong but I think it was a bad sensor more than likely.

 

[just1me]

I am using a 195 thermostat, I've read the 180 thermostat can possibly throw a code for running to cool, and also the gas mileage may drop.

 

[MidnightRebel07]

Yep, I think the new one they sent me when I ordered the complete housing with t-stat was a 180 because the temp gauge was always showing cooler than normal and the mpg's did drop but my trans was starting to go too so who knows.