PontiacBonnevilleClub.com

morning guys. Over these ten years i've had the bonneville, i've NEVER noticed the temperature act like how its acting. It always used to heat up to 200 f. over a course of give or take 10 minutes, and it would stay there through the entire drive until cool down. Over the past few weeks, granted the weather is much colder, i've been noticing the temperature coming to about 160 and staying there. If i turn my heat off while driving around town it will heat up (sometimes but rarely) to 200, but as soon as i get onto the highway or achieve highway speed for shorter than 8 seconds or so the temperature drops fast down to about 160 again. i'm also experiencing terrible gas mileage. Im only getting 275 miles on a completely topped off tank. 94 percent of the miles are highway speeds of 70-75. My dad suggested the thermostat was the case. i would love some insight.. thanks guys

1st off, it would be wise to allow more than 45 minutes from the initial post before bumping the thread <next day at least if it drops to the bottom>.

2nd, it could be a couple of things however. A thermostat <as mentioned> or even possibly air in the system. Has any work been done to the vehicle lately? Has it been consuming coolant?

RJolly87 wrote: A thermostat <as mentioned> or even possibly air in the system.

Sounds like a partially/stuck open thermostat. Air in system would do that also. Like RJ said we need more info as far as any work being done to car recently.

no work has been done to the car.
the thermostat has 161k on it. i'm going to bet that would be my problem.

Good bet that its stuck open... Replace it with a 180 or 195<---- Stock Rating

Also if you have run like that for any length of time change the oil and filter... Running rich can contaminate the oil...

thanks for the tip jr