Weird problem here. Driving on the highway today the temp gauge pushed over 200 a bit. After a few minutes it settled into it's normal position. Came to a stop at the store and it rose above 200 a little bit more but did not go any higher. I let it idle for awhile to see it would raise any higher and it came back down to normal again for a bit. Took off and proceeded to drive around 45mph and it stayed normal until I stopped. It went above 200 again slightly then dropped to normal at idle. Coolant is at the proper level. I did here a slight "whirring" noise or grinding in the dash behind the cluster. Possibly a motor? Not sure.

Stepper motor in the gauge. In my best Yoda impersonation, Search and you will find these answers.

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Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck

Thank you sir. That's actually what I was hoping for.

I had the same problem recently with my 05 gxp still not fixed. Ended up being diagnosed as the had gasket and engine mount going bad. This was very bad news as it as around a 3 grand repair. I would at least look into this my temp gauge had the exact same behavior, and the gauge and thermostat were replaced and to no avail this did not help. Hope you get it figured out and it's not as bad as mine. Best of luck!

A lot of people jump to the head gasket issues right away as that is an old N* problem. They almost see $$$ signs when you come in...

Whenever troubleshooting, unless it's painfully obvious, start small and diagnose the little things first and then work up to the big issues.

Broken front motor mount is a common issue on these vehicles (all Bonneville's). Do a search on hockey puck mount.

_________________


Retired Bonneville Owner and former GM Tech:
2004 Pontiac Bonneville GXP: Black/Ebony *SOLD*

Summer Toys: Combined 827 RWHP / 877lb/ft RWTQ
2004 Pontiac GTO: Impulse Blue Metallic/Black/M6: lots 'o mods, 415 RWHP / 405lb/ft RWTQ!
2006 Cadillac STS-V: Light Platinum Metallic/Light Gray/A6 - Spectre CAI, Magnaflow exhaust, Speed Inc. tune, 412 RWHP / 472lb/ft RWTQ

Daily Drivers:
2019 Chrysler Pacifica Limited: Mommy's new RGC
2015 Chrysler Town & Country Limited Platinum: Kids new RGC
2007 Chrysler Town & Country Limited: Sold to neighbor
2009 Pontiac G8 GT: L76, Sport Red Metallic
2003 Chevrolet Suburban 2500: Doeskin Tan - 8.1L Big Block... new plow truck
1999 Chevrolet Suburban: Sunset Gold Metallic - Daddy's winter beater and plow truck