Weird temp gauge issue

[mikeinmobile]

So temp gauge maxed out suddenly and info center said ac shut off due to high engine temp (ac was not on). I quickly hit info center to check engine temp and gauge dropped instantly to normal and car was not running hot. Temp on info center floated up and down between 185 and 212 but never climbed past 214. Definitely not running hot. Cool evening so no air on when this happened. in fact we had heated seats on.



Drained most of coolant and changed the thermostat (cheap oreileys) and it wouldn't open, couldn't get warm air to blow from heater and lower hose cool and limp while upper hose hot as hell. Put a better (napa oe) stat on, it too doesn't want to open but engine definitely getting hot.



Took stat out and fluid finally flowing well. Drove 50 miles, mostly hwy at 80mph and temp riding up and down between 165 and 197 w/ac on (warm day here on Gulf Coast). ac shuts off same warning on info center but this time gauge drops all way down and temp reads zero. Car definitely not running hot but it won't allow ac to be on. Again, car is not running hot, you can hold the radiator hose after a 50 mile warm day drive.

[mikeinmobile]

I tested the napa stat in boiling water and it opens but seems a little slow. Is it possible the dry engine isn't letting the stat open due to no coolant to heat it up? I definitely have a gauge issue either way.

[mikeinmobile]

after letting her sit for hrs still reads ac off due to high engine temp at start up. Obviously car is completely cooled down

[Mr_Draco]

If this happened suddenly, the temp sensor could be bad and sending false readings.

[mikeinmobile]

Unhooked battery and reattached and temp gauge reset (ac working again) but now tire sensors reading zero. Still need some advice on why tstat isn't wanting to engage.

[Mr_Draco]

Originally Posted by mikeinmobile

Still need some advice on why tstat isn't wanting to engage.

It really sounds like the thermostat isn't the issue. Sounds like the temp sensor is the issue, especially if the car is reading high temp on a cold engine.

[SummitWhite11]

How long did it take for you to replace your tstat? I for the life if me could not do it since it's placed in the back of the motor. Ridiculous if you ask me. Ended up taking it to the shop instead.

[Valkyrie14]

I have had this randomly over the years. It is likely your engine temp sensor. It is located next to the exhaust manifold/headers on the drivers side of the engine block. I have replaced the sensor and harness on mine. It seems to have worked, but I still occasionally will get the warning. Another trick is to disconnect the ECM harnesses briefly and reconnecting them for a reset.

[mikeinmobile]

Originally Posted by SummitWhite11

How long did it take for you to replace your tstat? I for the life if me could not do it since it's placed in the back of the motor. Ridiculous if you ask me. Ended up taking it to the shop instead.

That is irritating. The V-8 is on the front face of the engine and is the easiest stat replacement ever.

[mikeinmobile]

Originally Posted by Valkyrie14

I have had this randomly over the years. It is likely your engine temp sensor. It is located next to the exhaust manifold/headers on the drivers side of the engine block. I have replaced the sensor and harness on mine. It seems to have worked, but I still occasionally will get the warning. Another trick is to disconnect the ECM harnesses briefly and reconnecting them for a reset.

I disconected neg bat term and everything reset and is working normal for the last 50 miles (w/AC on).

[mikeinmobile]

I'm running w/o thermostat and temp stays below 170 even w/air on. I see a procedure for stat change that says after draining coolant and installing stat, set heat in cabin to high, top off radiator, put cap on, drive vehicle, monitor fluid level and add as needed.


I originally put 2 different stats in and topped radiator and ran w/radiator cap off (like I've always done w/every car I've ever owned) and neither stat wouldn't open even when engine temp hit 250 so I removed stat and everything flowed. So I'm gonna follow this heat on/top off/cap on even though system will not be near full procedure and see what happens. I'll post results

[mikeinmobile]

Originally Posted by Mr_Draco

It really sounds like the thermostat isn't the issue. Sounds like the temp sensor is the issue, especially if the car is reading high temp on a cold engine.

Stat was not the issue. But apparently when changing stat on this vehicle, new stat will not engage if you top off radiator and run w/radiator cap off waiting for engagement and topping off like every vehicle I've ever owned.



I saw a procedure that says top off radiator w/heat on high (engine off), put radiator cap on and test drive, add fluid as need. Seems odd to me that you can't fill the system w/o a partial fill, drive, cool down, top off. But I'm gonna try it