I had the check engine light and the code 128 for coolant temp/thermostat. I read the forums and accordingly replaced the thermostat.
I filled up the coolant level, and the reservoir.

Guess what happened today? Its only a few days after the replacement. But I am getting the check engine light again!!

I also noticed the coolant temp in the dash readout went blank when the check engine light came on.
I went out and checked the coolant level again, and the reservoir has plenty, but I did need to top off the fluid.

Can the new thermostat go bad that quickly? Or can I now look at the ECT sensor?

 

may have an air pocket , or could be the temp senser

 

Could be trash from the old thermostat has wedged open the new one. When a thermostat goes bad, usually it's because the rubber gasket has come apart. If any of these rubber parts are left in the cooling system, they can then circulate around and become wedged in the new thermostat.

 

It would be well worthwhile to burp the system again. If that didn't resolve it, I'd drain and flush several times with water, then refill. As Firemangeorge says, leftover gasket material can jam the new one open. I believe we have had a couple members experience that already.

 

Yeah, it turns out I had an air pocket. Thank you

 

Glad we could help.

 

I have heard that some people drill a 1/8 dia hole in the stat to allow air to bleed from the system when refilling.

 

LOL - oh no - don't start that again. Someone might actually believe it's a good thing to do.

 

they put in a small hole if it does not have a jiggle pin, check valve or vent slot. Ever read this?
http://www.stant.com/consumer-produc...of-thermostats

adiós,au revoir, rrivederci

 

I have 3 used t-stats in my tool box, none of them has a bypass pin,valve or slot.