Replacing thermostat, do I need extra coolant?

[FlipTrac_511]

Hello folks! My 04 threw a P0128 code and, thanks to this website, learned that I need to replace the T-stat and that there's a project to brief me on it. My question is, should I expect to lose a lot of coolant in the process? Just wondering if I need to go out and buy coolant and distilled water.



Thanks in advance...!



P.S. Belated Merry-Xmas, Happy Holidays. Happy New Year!

 

[Mark Potterf]

I changed mine two weeks ago. I drained it all the way and replaced it with one gallon yellow antifreeze and one gallon distiled water.:banana:

 

[FlipTrac_511]

Thanks mark, but does it have to be drained? The dealership flushed it not too long ago.

 

[Jerry Gerner 2]

You shouldn't have to drain it but when you're done replacing the thermostat check the antifreeze and top it off just to be safe.

:banana:

 

[Gavin Allan]

If it were my truck, I would drain and do a new refill. You probably don't know what brand of coolant the dealership put in it, and I would not want to mix coolants.



However, you probably "could" just drain it down, change the stat, pour it back in just fine.

You will probably lose a little coolant and have to add a bit of water, but it "probably" will be OK.

 

[Brad Schultz 2]

Changed mine by draining about 3/4 gallon or less and simply replaced in back into the system when I was done. Lost very little in the swap.

 

[FlipTrac_511]

Thanks for the replies.



The check engine light disappeared last night. Does this mean it fixed itself or reset? I thought it would stay on until I had replaced the thermostat.

 

[Jerry Gerner 2]

Just because it went out doesn't mean it fixed itself.

 

[Gavin Allan]

Maybe the bulb burned out?

 

[FlipTrac_511]

The bulb isn't burned out, the CEL still turns on before I start the engine, then it turns off once running.



I'm going to tackle this project this morning. Am I supposed to "reset the computer" or something? If so, how do I go about this? Just disconnect batt?

 

[TrainTrac]

Am I supposed to "reset the computer" or something? If so, how do I go about this? Just disconnect batt?

Yep, just disconnect the negative battery cable and leave it off for around 30 minutes, or the duration of your repairs, whichever is longer. That'll clear the codes.



Just a thought: If you're replacing the thermostat, you might want to consider replacing the thermostat housing also while you've got everything apart. It's a high-fail item in the 4.0L V6. It's not very expensive from Torrie, and there's a project on this site showing how to accomplish this.

 

[FlipTrac_511]

Thanks Train Trac.



This project is done. Thank goodness for this site and the projects submissions for taking much of the guesswork out of this DIY.



Thank you, thank you, thank you, MYST.COM!!!

 

[Dreman]

I had to do the same thing recently. The weather is the main reason the light went out. When it's hot enough to warm the engine without a thermostat, the light goes out. It especially helps if the AC is used to warm it up even more. When it's cold out, the engine stays too cold for too long for the engine management system to be happy, and the CEL is activated. A couple of warm days will turn it off again.

 

[FlipTrac_511]

Hmmm, just before the CEL, SoCal has been experiencing an unusally colder winter than in recent memory. The old T-Stat looked okay to me but I had to change it out for piece of mind's sake.