[Chris12]

So this week, my Malibu scared the crap out of me and is making me paranoid. The temp gauge climb to 5/8 (ish, slightly higher that the picture below) on the gauge with no check engine light. Usually, it sits a hair above center regardless of the environment. This is the first time this has happened. It even showed me "Low Coolant" on the radio but went away after restarting the car. So, I am thinking I am running low on coolant. Checked the overflow tank. At the full line. I check the codes and I get the following: C0561, U2100, U0073, U0101, U0140. All focused on a control module. I made it back home by having the heat on blast and it stayed centered the whole time. When I turned it off during the last 5 miles of driving, it got up to the attached picture (223 according to the code reader). Now, I live 40 minutes from any real town smack dab in between LA and Vegas. I will drive locally but only drive to Barstow maybe twice a week. I am about to default by taking it to the closest chevy dealer (65 miles away), but I wanted to see if anyone has any ideas. Bad module, bad sensor, flush to the cooling system?

The car has 150,500 miles, year old water pump, fresh oil change, etc. It has never caused me this kind of problem. I really only need to last 3 more months before I put it on a trailer and go back home to IN where I have my truck.

 

[DrivenDaily]

First thought I had was low coolant and/or failing t-stat.

 

[Chris12]

First thought I had was low coolant and/or failing t-stat.

Didnt think T-stat... Something I am trying to find is if the issue with the codes could screw with the gauge like what it is doing now, but than again, why is the eng temp reacting to when I have the heat on full blast? Which would point more to a mechanical issue rather than a electrical one. I need to stop for the night before I go insane and in circles.

 

[Darthz]

Check out if the fans are coming on aswell.... and get whats called a fail safe t-stat....never hurts to change them...and are cheap

 

[Chris12]

Check out if the fans are coming on aswell.... and get whats called a fail safe t-stat....never hurts to change them...and are cheap

The fans do come on. I did check that. The low coolant warning and the codes baffle me, but the Tstat seems to be the main problem... I hope.

 

[Chris12]

Something I did think of. Are the fans one speed or multi speed? If multi speed, when does low and high settings come on? I have not found anything on it.

 

[DrivenDaily]

When Low speed is requested, the fans run in series. When High speed is requested, they run in parallel.

It works the same as having 2 light bulbs wired in series. If you hook them up so that juice goes to one, then from the 1st it flows to the 2nd, and from the 2nd it finally flows to ground, the 2 of them will be at about ½ brightness. The total will still be 12V, but each will "see" only 6V of it. The two fans together will still draw the same amount of amperage because they're spinning at only ½ speed.

The same happens in reverse with flashlight batteries. You put two 1.5V AA into the light and it gets 3V at the same amperage that the battery is rated. If you put them in side-by-side (in parallel), the light will get only 1.5V but it'll have twice the amperage available to it, so it can stay on longer before the batteries are dead.

 

[Chris12]

When Low speed is requested, the fans run in series. When High speed is requested, they run in parallel.

It works the same as having 2 light bulbs wired in series. If you hook them up so that juice goes to one, then from the 1st it flows to the 2nd, and from the 2nd it finally flows to ground, the 2 of them will be at about ½ brightness. The total will still be 12V, but each will "see" only 6V of it. The two fans together will still draw the same amount of amperage because they're spinning at only ½ speed.

The same happens in reverse with flashlight batteries. You put two 1.5V AA into the light and it gets 3V at the same amperage that the battery is rated. If you put them in side-by-side (in parallel), the light will get only 1.5V but it'll have twice the amperage available to it, so it can stay on longer before the batteries are dead.

that makes sense. Do you know what temp triggers low and high settings?

 

[DrivenDaily]

I don't. I hope someone else will see this and be able to respond.

 

[Alan06]

When I bought my Maxx 4 years ago, it had about 150K miles and the "Low coolant" warning used to come on a lot for no reason. I tried cleaning the plastic overflow reservoir, but it never made a difference; the years of goop and grime had built up enough to cause the sensor in there to fail. Solution: I bought a new plastic overflow reservoir, which comes with the sensor built in. I also ran some radiator cleaner through the engine to flush out all the old coolant. With everything put back together, new reservoir and new coolant, the message never appeared again and my car doesn't run hot either.
This may or may not necessarily address the exact problems you're having, but it's not a difficult thing to do and it will eliminate the possibility of a faulty sensor. While all the coolant is gone, that would also be a great time to change the thermostat, which won't add much to the overall costs.

 

[DrivenDaily]

The only thing I might add is that when flushing all of the coolant and/or using a chemical cleaner, it might be necessary to change the water pump if it's not fairly new. I've had to change my water pump on two completely different cars after doing a flush. The cleaner was so good that it removed the gunk that was keeping the water pump seals from leaking.

In 2019, my 2011 V6 overheated. Hoping it was just a bad sensor I replaced it, but later discovered that the t-stat had actually failed closed. I changed it, all of the hoses, and the water pump.