Which is more frequent / likely? I'm gonna do them one-at-a-time anyway, so I'd like to do the leading suspect first.

Truck isn't over-heating, runs great. I have a cheapo scan tool so I can see what the OBD says the coolant temp is but I don't have anything to measure the actual coolant itself-- well maybe the wife's candy thermometer? (That's not right...or is it?)

Thanks in advance for any help.

 

I have exactly the same deal.
The thermostat isn't letting the cooling system heat up quick enough.
I'm replacing the thermostat and cleaned connections to the temperature sensor on top and behind the engine.......
Crossing my fingers!

 

Nice, keep me posted.

When are you planning to do yours?

 

this Wednesday

 

Bad T Stat is pretty common issue with the I5s as they age.

 

Yep. what the Doc said.

 

Thanks mkarns, thanks WR3NCHE4D, Thanks
Doc Olds

You guys cool with using that Prestone "Any Color" compatible anti-freeze? Or should I stick with a labeled "Dex-Cool" product?

Thanks!

 

Years ago I had a friends father who would come by and see me under the hood of my old clunker (62 Desoto or 58 Belair 4dr) and would say
" hey Chris hows the car running?" me ""or its running pretty good"" him "hmm then get the Hzll out from under the hood" moral of the story.... He always did the same thing and said the same thins even in my 20's, 30's 40's lol!

If aint broke dont fix it....

 

Yes sir, understood.

Unfortunately, as the thread title implies, the truck is throwing a P0128 code and thereby, will not pass state inspection. Minimally, it is required that the thermostat be replaced, quite possibly the coolant sensor as well. But, I too subscribe to that old wisdom you speak of, but with a twist, "If it ain't broken, don't break it."

Modern cars sometimes need to be fixed when they ain't broken.

 

I use Dex-Cool, buy it in the 50/50 already mixed. You will need about a 1.5 gallons by the time you are done swapping out the old T Stat, so either buy 1 gallon coolant only and mix it yourself, or buy 2 of the 50/50 pre-mixed.