[grimmtimm78108]

I was driving home Thursday morning, 4 miles from the gym to home. Had only driven from home to gym after car sat all night. Dash read Coolant ---° F. It didn't say that when I left the house originally. I park and roll down my window, I hear the fan under the hood is on high. So, I had a mechanic check it out, says OBD reads a thermostat malfunction. Replace the thermostat, coolant temperature is populated. I get in my car the next day, start the car, fan is on high within seconds and coolant is ---° F. I disconnect the negative, reconnect a few min later, everything is fine.
Brief car history: I bought it used 40k miles ago, no major problems to speak of, A/C compressor went out 30k miles ago and I never got it repaired (what's the point, I live in South TX). Regular oil changes, new camshaft position sensor in 2020, new transmission hose (?) 2022. Not sure if any of that matters, I just take good care of my car.

Anyone have a similar issue that can help?

 

[1966tbird]

Poor connection between t sensor and the ECM or a dirty connector or a bad t sensor.
All the computer /ECM knows is that the temp does not ramp up fast enough or doesn’t get a valid temp reading. When this occurs, the ECM logs it as an error, messages the BCM, the BCM flags the instrument display, and the ECM /BCM turns the cooling fan on high to keep the engine from over heating and displays —-F

this could be a very simple fix of cleaning / adjusting the t sensor connector, removing the ECM connector and reconnecting several times to clean the contacts and coating the contacts wit a contact cleaner & silicon lubricant, to replacing the t sensor

there are posts here on the forum with detailed images, locations,with tips and tricks.

enjoy

 

[grimmtimm78108]

Thanks! So, I went ahead and checked out a lot of the posts and responses from this similar issue and decided to change the two cooling fan relays and coolant temp sensor, topped off the coolant after cycling it through, burping it and letting it cool. I'd disconnected the neg batt cable before I undertook the changes and have driven it about 6 miles total so far, so the temp is still populated, for now. 🙏

Based on what everyone else has said about these same 4 changes (thermo, CTS, relay x2), I won't feel successfully confident until I see the coolant temp remain populated for longer than 22 days. I visually inspected the wiring and where it connects to the ECM and the CTS and didn't notice anything unusual or concerning so I pray I've reached the conclusion of this particular problem.

 

[1966tbird]

One thing to look for is a sticky thermostat. They can lock open or closed. If it locks closed, the engine temp will skyrocket, locking on the cooling fans and finally post the —-F error.

if it locks open, then the computer will determinethe engine didn’t come up to operating temp quick enough then it locks the cooling fans on sets the error code and displays the wonderfully helpful
—-F on the info display.

so enjoy the fact you did good and solved your problem for minimal out of pocket bucks!

 

[grimmtimm78108]

Day 5: the temp is at ---° F and the fan runs on high. 🙄

I'm nothing a pattern, though. It didn't do start again until after this cold front came through. Warm days, had no problem. Also, when I cold started my engine, it fired right up but then a couple of seconds after ignition, the rpms dropped for about a half second, revved up slightly (1000 rpm) and then idled normally. Unsure if they're related but at this point, I'd believe it. How would one test for a sticky thermostat and is that a common occurrence with new thermostats?

 

[Mikegonzo79]

I was driving home Thursday morning, 4 miles from the gym to home. Had only driven from home to gym after car sat all night. Dash read Coolant ---° F. It didn't say that when I left the house originally. I park and roll down my window, I hear the fan under the hood is on high. So, I had a mechanic check it out, says OBD reads a thermostat malfunction. Replace the thermostat, coolant temperature is populated. I get in my car the next day, start the car, fan is on high within seconds and coolant is ---° F. I disconnect the negative, reconnect a few min later, everything is fine.
Brief car history: I bought it used 40k miles ago, no major problems to speak of, A/C compressor went out 30k miles ago and I never got it repaired (what's the point, I live in South TX). Regular oil changes, new camshaft position sensor in 2020, new transmission hose (?) 2022. Not sure if any of that matters, I just take good care of my car.

Anyone have a similar issue that can help?

Was having the same issues and replaced everything you did. Still happened after a while so I replaced the water pump and haven’t had any issues. If yours still does that replace the water pump cause that’s what’s happening.

 

[1966tbird]

Just one problem to concider

The test of a tstat is more expensive than to just replace it.
A common problem is the rubber seal gets folded under the moving metal of the tstat and blocks the tstat open. This allows cooling water to circulate through the engine when the engine is cold. By doing this, the engine does NOT come up to temp quick enough and the system flags a cooling system error….locks the cooling fan on and disables the AC clutch.. ie no AC in Texas…big bummer!

and a new tstat can fail right out of the box. I managed less than 1000miles on a new DELCO when I replaced the engine.

From Wonderful Waxahachie
Enjoy

 

[Mikegonzo79]

Just one problem to concider

The test of a tstat is more expensive than to just replace it.
A common problem is the rubber seal gets folded under the moving metal of the tstat and blocks the tstat open. This allows cooling water to circulate through the engine when the engine is cold. By doing this, the engine does NOT come up to temp quick enough and the system flags a cooling system error….locks the cooling fan on and disables the AC clutch.. ie no AC in Texas…big bummer!

and a new tstat can fail right out of the box. I managed less than 1000miles on a new DELCO when I replaced the engine.

From Wonderful Waxahachie
Enjoy

Your correct about that and I had replaced numerous tstats and sensors. That’s why I changed the water pump out and my issues went away.

 

[Crowson81]

Poor connection between t sensor and the ECM or a dirty connector or a bad t sensor.
All the computer /ECM knows is that the temp does not ramp up fast enough or doesn’t get a valid temp reading. When this occurs, the ECM logs it as an error, messages the BCM, the BCM flags the instrument display, and the ECM /BCM turns the cooling fan on high to keep the engine from over heating and displays —-F

this could be a very simple fix of cleaning / adjusting the t sensor connector, removing the ECM connector and reconnecting several times to clean the contacts and coating the contacts wit a contact cleaner & silicon lubricant, to replacing the t sensor

there are posts here on the forum with detailed images, locations,with tips and tricks.

enjoy

Hi this is Erica.
I am getting ready to pour some engine oil stop leak {Lucus} and change my oil. It is leaking on the ground now. I will take pictures as i go. I really need some help. Thank You... I will return....