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Bad thermostat in 2000 pontiac sunfire?

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May 17, 2007, 8:47 AM

Post #1 of 2 (5261 views)
post icon Bad thermostat in 2000 pontiac sunfire? Sign In

Hi everyone,
I dont know much about cars so please excuse me if this sounds like random babbling. A few months ago, (prob in feb), this red light comes on in the dashboard indicating low antifreeze. For awhile I ignored it and my dad filled it with antifreeze. This happened consistantly until March or April, until the red light came on almost every other day. Suddenly, my car began to lose antifreeze and need a refill once or twice a week. There was no leakage shown on the driveway at this point. A few weeks ago, I was driving to my boyfriends house and my temperature gauge went insane and smoke was erupting from the hood of my car. The radiator hose was torn, so my dad replaced it. The red light did not come on for several days, and on again it came. After that, my dad put alumniseal(?) on something (I dont know what) and the red light did not come on until 3 days later (today). My radiator is new, so I dont believe it is a leak in the radiator. I have witnessed 2 leaks on the driveway, which is probably antifreeze, and these have both occured since my dad put alumniseal in my car. My temperature gauge is consistant most of the time, but the past 2 weeks it flucuates a lot. My car has overheated before in the past. Sometimes it will go up really high then suddenly drop. This morning, the temp gauge shot up, then went back down, and the red light came on, and stayed on until my 40 min drive to work was complete. We do not believe it is the headgasket. My dad now seems to think that the thermostat may be bad and causing coolant to boil out of the radiator. Does this make any sense at all? And if so, do you believe this could be the problem? Thanks in advance if you can provide any input.

Edit: By the way, my A/C and heater are working fine.

(This post was edited by amjysu on May 17, 2007, 8:56 AM)

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

May 17, 2007, 3:59 PM

Post #2 of 2 (5247 views)
Re: Bad thermostat in 2000 pontiac sunfire? Sign In

Sorry to say but if you drove 40 min starring at an overheat light you probably do need a head gasket by now or perhaps the head too.

Whatever caused the leak to consume anti-freeze will trigger the low anti-freeze light or low coolant or whatever it says. That's different from overheating but will cause it.

A thermostat that won't open is pretty easy to diagnose. The car heats up but the radiator stays cold/cool and has no circulation thru it.

When it used anti-freeze without evidence is a clue that the engine is burning it and if slow enough won't make smoke but that is almost always a head gasket or head problem. Pressure testing system should help pin point the problem(s),


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