Normal operating temps

[captain150]

So I've done some searching on this, though most are about winter driving or cases with clearly bad thermostats. Some background;

I have a 2009 4.2 with about 130k miles. I replaced the original OEM t-stat a couple years ago with a genuine AC Delco 192F.
In both cases the temp gauge is ever so slightly left of center, and a scan tool typically shows 80-85C (about 175-185F). Same for both old and new t-stats (and the original wasn't stuck open at all).
From my reading this seems a bit low, but the truck warms up fast, and even in my brutal winter temps of -30C the engine can reach 180ish F, though of course warm up takes some time in such cold (normal for all cars).

Two overly eager thermostats in a row? Or is something else going on? When the ambient is really warm (like 90ish F) I start to see 190F or more on the scan tool.

Maybe I'm just overthinking it.

 

[TJBaker57]

So I've done some searching on this, though most are about winter driving or cases with clearly bad thermostats. Some background;

I have a 2009 4.2 with about 130k miles. I replaced the original OEM t-stat a couple years ago with a genuine AC Delco 192F.
In both cases the temp gauge is ever so slightly left of center, and a scan tool typically shows 80-85C (about 175-185F). Same for both old and new t-stats (and the original wasn't stuck open at all).
From my reading this seems a bit low, but the truck warms up fast, and even in my brutal winter temps of -30C the engine can reach 180ish F, though of course warm up takes some time in such cold (normal for all cars).

Two overly eager thermostats in a row? Or is something else going on? When the ambient is really warm (like 90ish F) I start to see 190F or more on the scan tool.

Maybe I'm just overthinking it.

Seems low to me. I run 206 to 215 by scantool. I only see the 215 stopped or just after engine shutdown. 210° F to 212° F in motion generally.

 

[Mooseman]

Mine runs pretty rock steady at 188f, moving up slightly when stopped and then dropping slightly below as the t-stat closes again. I replaced my original t-stat years ago with a Mahle (88c/190f). I also run a thermal fan.

Looking at different t-stats on RA, the temps are all over the place, from 187 to 192 for those listed as OE and 160 and 180 for alternates. The GM OE part doesn't show the temp however it looks exactly the same as the Mahle, which is 88c/190f. They didn't have the ACDelco listed although that is the case now as they show GM Genuine parts instead.

I think you're fine. If it seems to be the same as your old t-stat, I'd just leave it. I think that different thermostats have slightly different temps, just like men and women . They are controlled by a wax pellet so how precise can that be?

 

[TJBaker57]

the temp gauge is ever so slightly left of center, and a scan tool typically shows 80-85C (about 175-185F).

FWIW, the threshold for a P0128 code is 176°F.

If the engine coolant has not attained that temp and held it for 30 seconds in a time frame determined by the PCM the P0128 code sets.

If youe engine wasn't warming up appropriately the check engine light would come on the second consecutive occurrence of the condition.

So in short, since you're not getting the P0128 code you should be OK.

 

[captain150]

Awesome thanks for the replies. Yeah I've never had the P0128 code, so I'll let it ride. Changing the thermostat isn't that fun.