car just overheated, thermostat, something else?

[cam98aro]

hey guys, while driving today i noticed that i wasnt getting any heat, it was just blowing cold, and i checked the temp gauge and it didnt move at all.

while this happened, i stopped at a red light and noticed that my rpms were stuck at 1500, then they went down to normal idle. Every time i stopped after that, the rpms did the same thing.

Then all of a sudden my temp gauge started working and i got my heat back, but the temp starting going way up, i watched it carefully, and it was just about to hit the red, i went down a side street to pull over, and then the temp gauge fell back down to normal operating temp and everything seemed fine after.

does this sound like a stuck thermo to you guys?

I just thought it was kinda weird that my rpms were staying at 1500 for a few seconds while all of this was happening. The thermo is only about 2 years old, and my coolant looks great.

edit* also, what is the stock thermostat temp for a 98' 3.8l?

[bigairboarder44]

Re: car just overheated, thermostat, something else?

the stock thermostat temp is 195 for 95-98

[T-Mill]

Re: car just overheated, thermostat, something else?

You probably have some buildup... start the car and let it idle for a few minutes, the amount of time it would take to reach normal temp, and feel your radiator hoses... the should be HOT... if they aren't it could be a bad thermostat, and since they're cheap you could replace it anyway, but if that doesn't fix it I'd flush the system...

[cam98aro]

Re: car just overheated, thermostat, something else?

You probably have some buildup... start the car and let it idle for a few minutes, the amount of time it would take to reach normal temp, and feel your radiator hoses... the should be HOT... if they aren't it could be a bad thermostat, and since they're cheap you could replace it anyway, but if that doesn't fix it I'd flush the system...

yeah, im planning on replacing it tomorrow, i just thought that it was weird what happened, i am assuming that the temp sensor is after the thermostat?

usually a stuck thermostat will cause the engine to overheat instantly, and not read nothing on the temp sensor, at least from my experience.

[T-Mill]

Re: car just overheated, thermostat, something else?

yea that's the reason why I was thinking a clog/partial-clog... I feel like I've had 50 problems with my cooling system and it acts different, and is caused by something different each time... lol

[cam98aro]

Re: car just overheated, thermostat, something else?

yea that's the reason why I was thinking a clog/partial-clog... I feel like I've had 50 problems with my cooling system and it acts different, and is caused by something different each time... lol

yeah, i have had no problems, but i am positive you are right and something was blocked because i was getting no heat.

all of the hoses and thermo were replaced not long ago and i did a flush with the green stuff.

my engine likes to drink a bit of coolant while driving so i add some every few months, it is usually clean

[ssms5411]

Re: car just overheated, thermostat, something else?

I would test your fans to make sure their working also. Just turn the A/C on and they should turn on. Are you using Dexcool still or have you swapped to the green coolant?

[cam98aro]

Re: car just overheated, thermostat, something else?

I would test your fans to make sure their working also. Just turn the A/C on and they should turn on. Are you using Dexcool still or have you swapped to the green coolant?

yeah, while i saw the temp go up, i turned the ac on along with the heat.

i think the temp rose so high is because the thermostat finally opened up and the coolant before was so damn hot it made the temp rise really quick, then it went back down after everything evened out.. at least thats my guess.

i took the dexcool out probably 3 or so years ago, i use prestone extended life 50/50 to be exact

[cam98aro]

Re: car just overheated, thermostat, something else?

just started the car and drove for a bit, everything seemed 100% normal.

I think it was just a freak thing, but for $10 and 30 min im going to replace the thermostat.

[cam98aro]

Re: car just overheated, thermostat, something else?

did the same thing again today, i replaced the thermo, the old one was a lot harder to press down than the new one was, def. think that was the cause

[debord97]

Re: car just overheated, thermostat, something else?

yea i was going to say a sticky thermostat

[cam98aro]

Re: car just overheated, thermostat, something else?

yea i was going to say a sticky thermostat

the only thing that confused me was why the car didnt overheat.

im assuming the coolant temp sensor is after the thermostat which was preventing the coolant to circulate and the temp gauge from moving.

[debord97]

Re: car just overheated, thermostat, something else?

could have been a fail safe thermostat. they will screw up but somehow not in the closed position. not sure exactly how they work but everytime i replace one in a vehicle my friends always remond me to get a fail safe thermo. think they cost a bit more but i guess it's worth it.

[ssms5411]

Re: car just overheated, thermostat, something else?

Fail safe will lock open if it fails which is always a good idea to get one, esp here in AZ or any hot state.