Hello, I have a 2007 Hummer H3. I had a cracked radiator so I replaced the radiator, also replaced the thermostat and made sure to add the right dexcool and got the air out.
before my radiator cracked and started leaking the temperature was always under the half mark. now the temperature is always raising between 3/4 and little less.. which I never seen it goes that high before. if the car is off and I start it, the temperature gauge will be at 3/4 then it goes down to like the pic I attached which is little below 3/4 and kinda stay around there. no matter what the temperature is 70 or 90 its the same. I live in florida and it gets really hot and humid so I wanted to figure this out before we start getting super high temperatures. the new thermostat that I installed is gates 34045 which open at 187 they say. I don't know what's the opening for the stock I heard 190?? but could it be the thermostat is bad? because if it open at lower temperature then it should be less than the half mark for sure...

 

Either buy a bluetooth device and get the Torque app (free) or get a tuner that can plug into the OBDII port that will read the true temp of your coolant.
The "idiot gauge" really can tell you/us/them nothing about the real coolant temp.

 

whats the name of that Bluetooth device?

 

Search GOOGLE for Bluetooth Torque compatible with your phone.
Plenty of posts here for them too.

 

Ok whats the temperature suppose to be or not suppose to exceed? Also why when I turn off the csr while it’s hot and turn it back on the indicator be at 3/4 then start dropping slowing ton
between 3/4 and 1/2

when I made more research the thermostats that come equip with hummer is 180 degree but the new version is 192. I looked everywhere for he original one or to see if dealers have new old stock but no one have it. Any idea where to find it ?

 

This topic has been beat to death by a ton of paranoid people. What you are seeing on your "idiot gauge" is completely NORMAL! Search it out.

Everybody and their brother that changed the factory T Stat to a replacement sees a now slightly higher temp on the gauge. When I said idiot gauge, that is what that dash gauge is, like and idiot light with a needle. Not very accurate and does not need to be since 3/4 temp is not an issue. When it points to the red, that would be too hot. Changing T Stats to try to lower it is a waste of time and $. The factory PCM is set to achieve around 193 to 205 F temp, that is the sweet spot for emission reduction without suffering performance loss. Everybody's H3 is going to be slightly different because of miles, coolant quality, driving habits, dirt in the radiator and condenser.....

Once you look at the actual temp via a scanner, if it is in the above range, life is good.

Search the three levels of overheat protection the H3 has which will all be displayed in the DIC long before an overheat ever occurs.

 

Pretty basic auto cooling 101..... see: 2006 Hummer H3 over heating to 3/4 when parked.

 

Doc you should make that thread a sticky!

 

Check temp with a scanner! If your gauge is accurate that would be pushing boiling point. I would NOT recommend driving at that temp for a long time, premature wear on engine and trans components. I just checked the accuracy of my 07 gauge and this is the max the gauge reaches no matter where I drive:

 

Just like to add that the old thermostat could have been opening much too soon. This is also common with the H3's I5 Atlas engine. There have been many thermostats changed due to no heat in winter and check engine lights. My temp gauge running under half because of this. The old failing thermostat running cold compared to new stat operating properly. I have checked my gauge with a quality scan tool and at 3/4 it was reading 207°F after bombing down the highway and coming to a light. Just a reminder that pressurized coolant boils at over 220°F. If my idiot gauge doesn't go to the red everything is fine, just like the Doc said. Drive on.