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Driving home tonite on the highway the Service Engine light came on and stayed on.

It's been colder lately and the engine hadn't been heating up all the way, so I figured the thermostat was sticking partially open.
Pulled the codes at Autozone and sure enough it was a P0128- coolant temp always low.

Never been so happy after pulling a code <grin>.

So how much antifreeze will leak out if just pull the thermostat housing without draining any? I read somewhere up to a 1/2 gallon, but that doesn't seem right.

1/2 gallon sounds right. Everything in the cooling system higher than the thermostat will drain, including the top hose and the top of the radiator.

I just siphoned off a gallon or so. Probably way more than you need. Less mess, save the environment, yada yada yada...

Uhhh no. Not that much. Just have the end of the upper hose up in the air so none comes out after the initial take off and change the stat when the engine is completely cold.

These are also an option

I am not so sure on that, because as soon as you pop the thermostat out, it will just drain through the engine, right?

Im just going by what happened when I did mine twice. Coolant loss was a minimal, about a pint, no where near a half gallon.

If its that big of a deal, just pop the petcock and catch the fluid or siphon it out of the radiator with a hose.

01bonneSC wrote:Im just going by what happened when I did mine twice. Coolant loss was a minimal, about a pint, no where near a half gallon.

If its that big of a deal, just pop the petcock and catch the fluid or siphon it out of the radiator with a hose.

Yeah, I just did mine a few weeks ago, and I was in a MAD HURRY, had to get it done ASAP so I could get on a 200 mile road trip. I hadn't ever done it before, and like someone said above, if you hold the radiator hose up in the air after it comes off, coolant loss will be minimal indeed - and I didn't have a different car to drive, so I did mine HOT. Not that much coolant loss at all. .

Love the vise grips!

Last 2 cars I changed thermostats on there was no problem with coolant loss... no biggy though I'll just wade in and make a mess.

Just make sure none of the neighborhood dogs hit your garage...

00Beast wrote:Just make sure none of the neighborhood dogs hit your garage...

Any messes I do make, I clean up. A drain tub under the engine/trans works.

I forgot to ask....will I need to reset the code after replacing the thermostat or will it reset itself after a short time driving?

It should reset itself once the condition is solved, and like 40 some key cycles to clear it from your history.