Overheat! Thermostat????

[Redog]

OK this is an odd one.

I replaced my coolant bottle today thinking it wasn't holding the pressure, but the car did the same exact thing tonight.

Driving home from work I stop at a light and the temp gauge starts climbing, climbs past 1/2 way, except tonight it gets past 1/2 way and drops back down to normal. On the way back down I turn on the heat full blast and for a slipt second it was cold, but it got hot right away and the temp dropped faster.

The weirdest part about it, the only time it does this is at the same traffic light and stops doing it at the next same traffic light. My commute is only 6 to 8 minutes this time of night. I've done it in 4, but on the nights I do it in 4 or 5 mintues, this doesn't happen.

Now it doesn't do it at any other time. I can start the car and drive to the supermarket 3 blocks away and get stuck for every traffic light along the way and it's fine. Going to work today, it was fine and it was muggy out. Yesterday driving my son home and then to Pottstown (a 1 hour drive) and it was hotter and muggier and it was fine. It's only on that 1 strech of road, only at night and only when I leave from work. No other time :banghead:

I doubt any leaks, but I'm going to be changing my oil today or tomorrow and I'll see if it's milky or not. Coolant is still comming out of the overflow bottle. This is making no fucking sense :banghead:

[Afugy]

Try bleeding the air out of the cooling system again. Should take no longer then 5 minutes to get all the air out.

[Nate's Alero]

overpressure of the system... is the coolant black/brown? does it all barf out of the bottle? and when you rev the engine in park, sitting still can you hear like a water flowing sound?

[Ryan from Ohio]

Sounds like air in the system...

The tstat may be sticking also.

I would bleed it first, then replace the tstat as a precaution.

[Redog]

Coolant is a little dirty, but not that bad.

Changed the oil today (needed it) and it was clean

No air, I bleed the system yesterday after the new bottle was put in

[Nate's Alero]

Coolant is a little dirty, but not that bad.

Changed the oil today (needed it) and it was clean

No air, I bleed the system yesterday after the new bottle was put in
bleed again, there has to be air in it.

do a cooling system leak down test plz.

[Ryan from Ohio]

Did you run the heat while bleeding it?

Sounds like that is where the issue is at.

[zzyzzx]

When I did my LIM job, I never bothered to bleed it. I ran it a little with the cap off, then just drove the car with the heat on a few times with no problems.

[[ion] C2]

Did you run the heat while bleeding it?

Sounds like that is where the issue is at.
You know we have a blend door and not a heater control valve, right?

[Nate's Alero]

well, there IS air in there. losing coolant at all besides the puking out the bottle?

[Ryan from Ohio]

C2;546122']You know we have a blend door and not a heater control valve, right?

No I didnt.

I still run it to help verify all air is out of the system and the heat is working properly as it should.

Eh, guess you could wing it and hope all the air is out?

[Redog]

I do have the car running when I bleed the coolant. Should the car be hot? Cause everytime I do this the car is just started up.

When I do this coolant comes out right away

[Ryan from Ohio]

Well if its just coolant coming out your good then. I just verify its all working when I do this type stuff.

When is the last time you flushed the system out with flush?

Maybe its clogged up a bit?

Probably just the tstat sticking my guess.

[Redog]

T-stat was my guess too.

Flush was done 2 years ago with a LIM job, and I had another LIM 11 months later this past Feburary :mad2:

[zzyzzx]

Flush was done 2 years ago with a LIM job, and I had another LIM 11 months later this past Feburary :mad2:

And the reason for this was? Just curious.

[bigbiz15]

Hey mine is doing the same exact thing, when im driving my car for a little bit the thermostat will rise past the center and then just go right back down after a while. I still cant figure out whats wrong with it. After reading the threads though im going to try what you all suggested. As far as the coolant leaking out of your overflow, my issue was a faulty radiator cap that could not hold the pressure. So I changed it and now my coolant doesnt leak out

[[ion] C2]

So many different things that could cause this type of behavior. After my extensive amount of various cooling system issues, I can tell you it's a PITA to find them. I finally fixed all of mine. The most recent and long-term one it took me forever to fix ended up being a plastic heater hose quick-connect that cracked down the mold line, allowing pressure to escape, air to come in.