Check those Engine Coolant Temperature Sensors
 

Hey guys, I haven't provided a nice helpful thread in a while, and thought it was time.... My car has been running cool ever since I changed the original thermostat a few years ago (around 165 degrees or so). During the install of my GMR ported head about 1.5 years ago, I decided to replace the thermostat again (just so I didnt have to mess with it for a while), and the car still showed 165 degree temps. Dyno'd it, saw no ill affects, and said frig it. Well, over the past week or so, I noticed engine coolant temps hovering around 153 while cruising, and reduced fuel economy. I started reading up on the possible issue, and everyone always said change your thermostat, but I just couldnt believe the thermostat would take a crap on me in under 2 years and 7k miles. So I decided to look into what else could possibly cause the issue and that led me to the ECT sensor. I purchased a brand new Genuine GM ECT sensor for $17, installed it, and low & behold my engine temps are back to where they should be (around 176 degrees while cruising). My car always ran around 181 when it had the stock head and original thermostat, so I knew I was back in business. This is much easier than messing with the thermostat, so if you have low miles on your thermostats, and you determine it's functioning correctly, check the ECT sensor first before you go and change anything else.

Here's a quick how to.... note, you do not need to drain the coolant on the LSJ, simply remove the ECT sensor with a deep wall 3/4" socket, and replace with the new one. Follow torque specs and you are set. Make sure to do this when the engine is cold.

https://www.cobaltss.net/gallery/fil...21883348_n.jpg

Here's a pic of my original ECT sensor w/ 62k miles on it, and all gummed up with deposits:
https://www.cobaltss.net/gallery/fil...74313679_n.jpg

Part # for the LSJ sensor (2.2/2.4 have a different part #):
https://www.cobaltss.net/gallery/fil...46506453_n.jpg

Installed:
https://www.cobaltss.net/gallery/fil...14791429_n.jpg

Well i could happen that the t-stat goes bad specially if you replace with aftermarket i had to change mine in my basemodel almost every year because it would go bad

I only use Genuine GM replacement parts, but yes cheap aftermarket thermostats could go bad much faster. My factory thermostat lasted 50k miles, before it started to cause an issue.

That was not the case with my car this time though, and that's why I say to check the ECT sensor first, before just throwing parts at it.

Yup i was going to add a bad t-stat will usually not show the coolant temp tho so a bad sensor sounds like the best explanation in your case but very helpful info for sure

so, lets say car is not acting up...should we replace it? considering my 2.2 base has 115kl

If your coolant temp readings are normal... no need to mess with it.

Fyi, 2.2 ECT sensors are located back by the t-stat. Not as easy to replace as on the LSJ.

oh ok, my fuel ecomony sucks us my 02...I need to replace that somabich.

couldve been problematic for you with the amount of timing the gm stage tunes run + the added timing of a false, low ect reading while the car is actually at operating temp. not to mention that youve got fueling practically maxed out

A bad O2 sensor will cause poor fuel economy for sure.

OEM all day err day.

Yes sir!!

Ok, let's try this again.... Southal Cobalt I apologize for misreading what u were getting at. Thank you for clarifying and shooting me that PM. My car is constantly monitored via wideband, interceptor with alternating parameters, and knock warning lights. The gmrs3 tune although locked to tuning has full parameter logging access, which I know inside and out. My fueling is not maxed regardless of what some think (magical unicorns). Working hard for sure, but I have a nice steady afr throughout my entire rpm range. Yes, a false reading or failing ect sensor can have an affect on timing, I know this, and I appreciate you for adding this to the thead for others who may not understand tuning parameters. My car was never in any danger though. The original point of this thread was to make people aware of other issues that can cause a low reading for engine coolant. We all got off on a tangent, so let's pull back together. Thanks guys!

For experiments sake, I wonder if you cleaned the crud off of the old one and put it back in, if you would see better readings.

They do degrade in performance over time but if you were to just sand down the original one and re-install it might work just fine, as in your case it wasn't a circuit fault.

To be honest Joe, I thought about that, but for $17, couldn't pass up a brand new genuine gm sensor :)

I think I cleaned it once before I reinstalled it into my GMR head, but it didnt last long before the temps started dropping again.

Temps have been holding steady between 176-180 with the new one. Gas mileage is back to.

yeah, for the peace of mind..$17 bucks is worth it.

oh thats what that thing is right there haha

good info to know

:thumb:

Today I was driving to work and noticed my cooling fan was running. It's pretty cool out so I thought it was strange. I checked the DIC and the coolant temp read ---. Does the DIC get the temp from this sensor? The reason I ask is I fired up my TORQUE App and it was reading around 186. If the cooling fan is triggered by this sensor and my temp is cooler that the trip point I don't want my fan running all the time.
Thanks

'06 Cobalt 2.4 SS

Well --- in the dic for my experience it has always been the thermostat

Yes, that is were the DIC get's it's info.

Are you tuned or anything? Did you have the defroster on? Kinda odd the fans are coming on at 186. Should be more like 221 before the fans come on. This doesn't sound like a coolant temp sensor issue.

Possibly a thermostat problem.

The crud that is seen on the sensor has no effect on the readings.

Inside that is hollow and is simply a .25 cent temperature thermistor.

Good call in replacing it. They do fail often on cars however, most cars either have two separate temp sensors. One for the ECU / PCM to read for adjusting engine parameters and a second one that is strictly for the displayed temperature on the cluster.

Some cars have a single sensor that has four wires which actually houses two separate sensors. One for the ECU/PCM and the other for the gauge.

EDIT: I did look up the schematics for an 07' SS and yes it appears that there is only one ECT sensor that is used by the PCM and the cluster gets the data from the PCM.

The most common scenario in general though is the 4 wire sensor or two separate sensors.

So my question to ya'll is, (sorry for reviving the dead) if my ECT sensor housing is slightly busted, so that you can just barely see the connectors when it's hooked up, do we see that skewing temps?

After replacing my timing set (which is when the ECT sensor housing was damaged), the temps are a little more reactive than they were before. climbing higher faster, but it still drops down to normal.

I am having the same issue, I see the photos are from an LSJ anyone have a photo of ECT sensor location on a 2010 LNF motor?

On the LNF it's in the thermostat housing on the back of the engine. It's the electrical thing sticking out of the bottom part in this picture. Sorry I don't have a picture of the part on the engine for you.

https://cimg7.ibsrv.net/gimg/www.cob...f846b866ae.jpg

Thank You