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Discussion Starter #1
Hey everyone,

About a month ago, I got a check engine light and decided to get the code read at Autozone. It came back as P0128 which is related to the thermostat ("Code P0128 indicates that the Coolant Thermostat had a fault (Coolant Temp Below Thermostat Regulating Temperature) for a predetermined period of time.

So as of right now, here are my issues. 1) Check engine light comes on intermittently. 2) Temperature gauge needle does not move when check engine light is on. 3) When the check engine light is on, and the needle hasn't moved, I get no cool air from the AC. I can get hot air with no issues, just no cool air. This whole problem is intermittent.

I took it upon myself to do some further research and decided to change out the ECT sensor. I thought I had let the engine cool off long enough, but obviously not, so when I got the ECT sensor off, coolant went spewing everywhere. Oops. So, I installed the new sensor and plugged it in. Now my issue is with the engine coolant level. This is pretty elementary stuff here, guys, and I know that, but I need a little assistance. I just went out and picked up some Prestone DEX-COOL and I'm a little confused as to how to proceed. Lol. Do I need to drain and flush the coolant? Or am I safe to simply mix and pour as much as I need to replace?

Thanks, guys!
 

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Old far...er...tinkerer..
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303 Posts
Hey everyone,

About a month ago, I got a check engine light and decided to get the code read at Autozone. It came back as P0128 which is related to the thermostat ("Code P0128 indicates that the Coolant Thermostat had a fault (Coolant Temp Below Thermostat Regulating Temperature) for a predetermined period of time.

So as of right now, here are my issues. 1) Check engine light comes on intermittently. 2) Temperature gauge needle does not move when check engine light is on. 3) When the check engine light is on, and the needle hasn't moved, I get no cool air from the AC. I can get hot air with no issues, just no cool air. This whole problem is intermittent.

I took it upon myself to do some further research and decided to change out the ECT sensor. I thought I had let the engine cool off long enough, but obviously not, so when I got the ECT sensor off, coolant went spewing everywhere. Oops. So, I installed the new sensor and plugged it in. Now my issue is with the engine coolant level. This is pretty elementary stuff here, guys, and I know that, but I need a little assistance. I just went out and picked up some Prestone DEX-COOL and I'm a little confused as to how to proceed. Lol. Do I need to drain and flush the coolant? Or am I safe to simply mix and pour as much as I need to replace?

Thanks, guys!
You probably woulda been better off with the 50/50 Dexcool - you wouldn't need to mix it with water. BTW, you're supposed to mix it with distilled water.

Anyway, pour some 50/50 into the reservoir, filling it to the hot line (while it's cold). After driving a bit, you will need to top it off, once any air in the system has worked its way out.

As for the initial diagnosis, if it's not the ECT, I'm thinking your thermostat is stuck open preventing the car from warming up.

Doug

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Discussion Starter #3
Hey Doug!

Thanks for responding! I went ahead and mixed the DEX-COOL, with distilled water btw, I had some laying around. I just did exactly as you said and all seems to be well. I turned the engine over, I no longer have the check engine light ominously threatening me (lol), the temp needle is about midway, and the AC blows cold. I'm waiting to see if it lasts before I get too excited though.

Thanks again!
 
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