Replaced a leaking thermostat housing (including a new thermostat) a few weeks ago with the metal one from Welch and now 3-times I got the P0128 error code - each time it was about 30F outside and about 10-15 minutes after beginning to drive.

Do I have a faulty thermostat? Is there something that I can do to try to fix this without the labor of swapping the thermostat?

In reality, it is only a dash light issue since the car drives fine. The light remains on until I reset it via ODBC; if it would not persist after shutting the car off it would be less annoying, lol...

 

Is your temperature gauge in the middle of the dial when this error occurs?
Can you hook up an OBD reader and check the temp on that.
Have you checked that there is not an air bubble in the cooling system; remove large plug on top of thermostat tower.
Did you completely change coolant when you changed thermostat tower.

 

Unplug the temperature sensor on the crossover pipe and clean the contacts. You may have splashed coolant on it.

 

RJ, going to try that first as it is the easiest

fredd60, going to try your bubble idea if the contact cleaning doesn't fix. Did not pay attention to the gauge, but it seems to measure slightly cooler in general since the repair, with the needle about 2-3mm below where it used to hover during normal driving.

The next time it happens I should read the coolant temp immediately via ODB2, is that what you were suggesting? What would constitute a normal temp? (aka. what am I looking for?)

The coolant was only topped off, but the coolant is all new due to an incident a month ago where the coolant supply tube popped off the engine block, emptying the entire coolant onto the ground...

 

I assume this problem happens every time you drive for more than 10 mins.
I would attach the OBD reader permanently, and have it showing water temp. every time you drive.

 

I'm not sure if this is related but I recently was getting low coolant warning. I added about a cup of 50/50 in the coolant bottle. About 2 weeks later I'm getting engine check and reduced performance. Coolant level is perfect!

We've had some unusually cool weather and with these warnings I've noticed the temp gauge not moving as it should have driving for a while so now wonder if I need to get thermostat changed. I can stop, let it idle for a while while in park, then start driving and then the temp gauge moves as it should.

Any ideas?

 

Classic sign of malfunctioning thermostat ;o)
These aer supposed to be replaced as a service item at least every three
years and considering they are peanuts, why wouldn't you ;o]
Also improves your fuel consumption.

 

I would think so as well but I have not gotten the errors today. So, makes me wonder if this is a continuation of the glitches I've seen for the last year.

 

Hi Morpheus, seems like the issue has resolved itself; could have been air bubble which worked it's way through. Temperature of my motor is usually 85 C to 100 C, but I don't sit in traffic a lot.

 

Yes! I would think if a real problem with thermostat, eng check light and reduced performance alerts would be on constantly.

I noticed this morning as I was turning abruptly into parking lot at work, it came on briefly and then went away so now wondering if it is the sensor in the overflow bottle.

 

Last night I got tired of the chk eng light and pulled the sensor from bottom of coolant overflow and seated it back in. No warning lights this morning.