Aveo5 has odd fan and thermostat temperatures

[GasSavers_Rotareneg]

I had just did a partial grill block of the lower grill by using pipe insulation foam tubes on the middle 6 segments of the grill:



The upper grill which is completely blocked with some coroplast.

With an outside temp of 45f and while moving at 60 mph the temperature would creep up to 198f (as indicated by my SG2) then the fan would kick in and drop it back to about 193f before turning off and repeating the cycle. I pulled the upper middle segment out and took it back on the road, where it stabilized at 190f. It used to stabilize around 184-186 depending on the outside temperature.

I looked up fan and thermostat specifications and was surprised:

The thermostat begins to open at 87C (189F) and is fully open at 102C (216F). The thermostat closes at 86C (187F).

The ECM will turn the cooling fans ON at low speed when the coolant temperature reaches 93C (199F) and high speed at 97C (207F).
The ECM will change the cooling fans from high speed to low speed at 94C (201F) and turn the cooling fans OFF at 90C (194F).

As far as helping the mpg, it did seem to help a bit, but as I only drove for like 30 minutes to check the temperatures I won't know for sure for a few fill-ups.

[VetteOwner]

yea thats about normal as overheating kills engines

[GasSavers_Rotareneg]

I was just surprised that the fan kicks in before the thermostat is even open all the way.

[GasSavers_RoadWarrior]

That does seem rather odd.

[Lug_Nut]

Is the spec for the t-stat "fully opens at 201F" or is it "is fully open by 201F"? Not semantics, there is a difference.
Thermostat construction is no so precise that I'd expect a linear response, and the amount of coolant flow difference between 199, 200 and 201 degrees is not likely to be worth discussing even if the thermostat's opening stroke were tied lock-step, like a servo, to the temperature rise and produced precisely 8.33333% of its total opening stroke per degree of temperature increase, or shut at 7.14286% of stroke per degree of decrease.

If there were one electronic sensor and electronic control of both the thermostat and fan, then it might make me pause to consider why, but with two sensors in two locations, and likely at two different temperatures because of this physical separation, I have no expectations that they don't overlap.

[GasSavers_RoadWarrior]

Gah, yes thinking about it, the fan sensor is usually at the "cold" side of the rad.

[GasSavers_Rotareneg]

I misquoted the fully open temp so I just copy-pasted them this time. The thermostat is fully open at 216f.