NoOne

Was driving this morning and temp would not go over 150 degrees.

Saw that the gauge for water temp was sitting at 100 and fans running at full speed.

Either the sensor failed or there is a wiring problem.

Does the meth kit wire into the harness where the temp sensor is? It's getting no reading at all and I wanted to check the wire.

Of course I'm not anywhere near home. Car drives fine but if its a simple wiring problem something I can fix here.

EcoBrick Bob

Your A/C also won't work....

Did you change out your T-stat, or remove coolant? If so, the system is VERY sensitive to being full and to any air pockets. Also, most aftermarket T-stat replacements have rim gaskets that will quickly fail.

To get the codes to delete and produce a temporary fix, disconnect the battery ground ( back right corner of car) and then drive your car in a lower gear until the car heats up to at least 170 for a short time. If it won't do that, you either have air in the coolant system, or the T-stat has failed.

NoOne

It is not the T-stat, it is either wiring or a failure of the water temp sensor.

It reads 0 degree's, no signal at all.

6Speeder

It's the thermostat, and the ECM reacting to it. If your ECT doesn't come up to the expected temp quickly enough the ECM will give you these symptoms.

EcoBrick Bob

When my T-stat failed (multiple times due to clearing codes) it goes to "0" on dash.

Did you change your T-stat?

NoOne

Thank you for the replies.

Dumb GM

Figure if it stopped listening to the sensor it would have put the SES light on.

The thermostat is fine, it was the weather and my driving. I believe the problem is the extended amount of time I drove the car and it never warmed up.

My normal commute it 32 miles to the office, 1/2 on side roads and half on the freeway. If its over 65 I run at normal temps but this morning it was 52 and my first 25 miles were on open 55mph roads

If I do not hit 165 before I get on the E-way it struggles to get warm. So all the driving at 55+ in cool weather it never warmed up enough and the ECU must have thought something was wrong.

Pulled the battery, back to normal.

I have a 170 degree t-stat which is probably too cold for the cold morning temps since its dipping into the 50's.

6Speeder

If you are running a 170 thermostat, it's probably damaged. Most of the available aftermarket thermostats have a rubber gasket that is different than the stock one, and it gets torn, not allowing the thermostat to fully close. I speak from experience, my second one has failed and I have to put the stock one back in, for the third time

For what it's worth, I can pull the Halltech intake (not as easy as the stock one), pull and replace the thermostat (only losing about 1 quart of fluid), and replace the Halltech intake in about 20 minutes.

Practice.

NoOne

Seeing it fail in what kind of temps?

I do not believe anything is wrong with the thermostat at all. It is the temps here.

If its over 65 the car runs perfect, goes up to 180-185 and sits there all day long, 190 with the AC on, or up to about 200 if I really beat on it.

When I leave my garage and its 45 out and get right on the freeway there is just too much airflow for the car to warm up. Thermostats do not pop open, they bleed as temps get near their rating.

A 170 degree T-stat is just too cold for the outside temps here. This morning it was 42 and I let the car warm up before I left. It was 155 when I left, and after 2-3 miles it was 165 and stayed there.

When its hotter out it works as intended.

Next year I might go up to a 180 degree. It doesn't run too hot in the 90's so 10 degree's is not going to hurt and will probably help a lot on cooler mornings.

EcoBrick Bob

Does the 170 Deg. T-stat that you installed have a rubber gasket that surrounds the edge of the T-stat? If it does, it is extremely likely that it has failed ( been cut by it moving in and out of the housing when it opens and closes). I have had 2 fail that way.

If you want to run the 170, you can take the bulb( brass portion) and place it into the stock T-stat housing after you remove the stock bulb. It will need to be crimped slightly to secure the bulb tightly however.

Also, make sure you get all the air out of your system by running the heater for at least 20 minutes and then adding additional antifreeze. I have had to top off mine several times. Our Vettes are very sensitive to low amounts of coolant.

While I am NOT tuned, if you have a custom tune, you can tune around this issue so that it will not code and cause this issue.

NoOne

I have the Jegs...from what I remember it is a hard piece, rubber, but not a soft material.

6Speeder

This is your key statement that shows you probably have a bad thermostat:

"This morning it was 42 and I let the car warm up before I left. It was 155 when I left, and after 2-3 miles it was 165 and stayed there."

A properly working thermostat would not stay open allowing the coolant temp to stay at 165, even if the ambient temp was zero.

You've got a bad one. Sorry about that.

RoadRebel

Huh? If it stayed there at 165 then it tells you that the element controls to 165 instead of 170.

davekp78

What does having the heater run have to do with it? I thought coolant flows through the heater core all the time.

6Speeder

No. It's proving that the thermostat is TRYING to control the temp, but as it's stuck open, it can't.

EcoBrick Bob

You can have air trapped in the heater core. This was the "Fix" in G8's which had T-Stat's changed. I had issues with my 160 deg T-stat that I modded per Mighty Mouse Thread, and have had NO problems/codes once I got all the air out and made sure the coolant system was really full. Had to add fluid 3 times, even though tank showed full+ each time. My car has the STOCK tune and has not been programmed to avoid coding due to 165 deg water temps.

Any T-stat that has a rubber gasket on the outside rim of the T-stat will eventually pinch/cut and fail. GM gasket is pressed into the metal portion so no way the seal can be damaged when it moves in and out. The reason it codes is because your car isn't heating up quickly enough, because the T-stat is leaking.

NoOne

I give up

If its colder outside and I let it warm up it will stay over 160 driving.

If its cold outside, and I drive it in regular side roads it eventually warms up and stays there.

If its cold outside and I drive it straight on the freeway, meaning cold, it stays cold.

If its over 60 degree's it runs just like normal.

The t-stat may be mismarked, or not accurate in where it is supposed to be. There is too much airflow and not enough heat being produced to warm the car in cold temps.

The code happened one time and no the car did not warm up but it has a lower temp T-stat, had the heat on, and it was less than 50 degree's driving over 65mph in 6th gear.

6Speeder

Don't give up, just pull your thermostat, you'll find it has a gasket that's failed, possibly not on the thermostat anymore, it's probably in the housing somewhere, with a piece keeping the thermostat open.

davekp78

OK, but you didn't answer my question.
Doesn't coolant flow through the heater core all the time? If so, what effect does turning the heat on do?

NoOne

It takes heat out of the coolant and will cool the engine.

6Speeder

It doesn't flow through all the time, it is valved and only flows when heat is asked for. However, when coolant is removed (like when you swap a thermostat) it's possible to get air in the heater core. You ask for heat to get the coolant to flow and move the air pocket out of the heater core.