07 Grand Prix base high Transmission fluid temperature

Xitmnt

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I have a 2007 Grand Prix base engine, and have noticed that the transmission temperature has gone up over 220 degrees during normal mixed local driving on a 90 degree day yesterday here in NY. According to the owners manual normal operating temp should be between 190 and 200. 223 seemed a little high. The fluid level is at max. Recently have done the trans service, cooling system flush incl heater core which was clogged, replaced thermostat, new trans lines to and from radiator, and just replaced the coolant bypass elbows, and bled the system. Engine temp gauge goes over half way after driving around for 30 min before going down below half way. Any advice? How high is too high for the transmission temp?
 

melsg5

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What was the engine temperature when you saw 220 on the transmission?
The new thermostat may be not opening correctly.
If you change it again, test the new one by suspending in pot of wster. It should start to open as it approaches boil and should be fully open at boil.
What do you mean by transmission service?
Did they drop the pan and replace the filter?
Are you checking the fluid level when fully warmed up, engine running, transmission shifted into each gear and then park?
 

Xitmnt

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What was the engine temperature when you saw 220 on the transmission?
The new thermostat may be not opening correctly.
If you change it again, test the new one by suspending in pot of wster. It should start to open as it approaches boil and should be fully open at boil.
What do you mean by transmission service?
Did they drop the pan and replace the filter?
Are you checking the fluid level when fully warmed up, engine running, transmission shifted into each gear and then park?
Thanks for the reply. The engine temp gauge showed just above the half line. The transmission service was dropping the pan draining all the fluid, new filter and clean screen and pan, fill with new fluid. I know to check fluid level at normal operating temp 190 to 200 degrees with engine running after driving it.
 

melsg5

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The only thing suspect is why does it take a 1/2 hour for your engine temperature to drop below the 1/2 mark? Thermostat issue?
Another thing to check is are any leaves or other road debris blocking air flow through the front of the radiator?
If you turn on the AC do the cooling fans come on right away?
The 223 is too high but it was a 90 degree day, keep an eye on that .
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Xitmnt

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The only thing suspect is why does it take a 1/2 hour for your engine temperature to drop below the 1/2 mark? Thermostat issue?
Another thing to check is are any leaves or other road debris blocking air flow through the front of the radiator?
If you turn on the AC do the cooling fans come on right away?
The 223 is too high but it was a 90 degree day, keep an eye on that .
I was driving around for 30 min, engine temp was below half until that point then went above half. Within 15 min engine temp gauge is below half then at the 25 to 30 min mark goes up to half then just above half then no lower than half for a while.
Usually takes trans temp 20 to 30 min to get to and over normal operating temp. The fans are functioning and coming on, the fans go on with the a/c.
 

Xitmnt

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Prior to all the cooling system work did your gauge do the same pattern of up and down?
Yes. The coolant was so old it turned to clay and clogged the heater core. I wonder if there are still blockages in the radiator even after all of it was flushed. Its a 2007 grand prix with 85k miles. We bought the car this past December and the previous owner never had the coolant changed.
 

melsg5

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Not sure how accessible the radiator is but you can rent an IR gun and look for hotspots.
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