Car overheating with engine off!!!!

[Cade93TA]

I noticed this because when I would get in my car for the first time of the day and run errands the car would run cool and great until I got out did my errand and got back in and started my car back up and drive home the temp needle would start rising more than usual. Then I would get home before it got into the red (by turning off the A/C) , turn off the engine then turn the key to the on position and the temp needle will rise into the red. and the coolant would boil in the reservoir.
Is this normal?
Have I never noticed this before?

Thanks
Cade

[Dave M]

If your car is overheating, it's best to run with the AC on, not turn it off. Turning the AC on causes the cooling fans to run regardless of the coolant temp. The car likely overheated after it was turned off because airflow through the radiator stopped (no moving air or fans on), but the coolant was near the boiling point and was still sitting next to a hot block which continued to heat the water for a few minutes after turning it off. It likely would have overheated if you kept running it, unless the fans had cooled it off.

Did you do any work to the cooling system recently? If so, was the system bled properly after the work? Air trapped in the system can cause overheating. Check the plastic air dam under the nose, make sure it's still there, check the front of the radiator for debris blocking airflow. Replace the thermostat and flush the system if it's been a while. Chnaces are your problem lies in one of those culprits.

[Kevin - Blown 95 TA]

Yeah, you should try to bleed the cooling system and see where that gets you. Do it a few times and keep the antifreeze level up. Hopefully, that's all it is.

[Cade93TA]

Thats kind of what I thought...
I have installed a manual fan switch because I didn't think my fans were turning on when they were supposed to. Now I use it all the time...it still overheats when it wants too.
I replaced the thermostat recently with one from O'Reilys (might be suspect) But it looks just like the thermostat in the picture being that gets posted on this board.
Air Dam is Still there
Reverse flushed the system


I think your right about the bleeding of the system...maybe I need to spend more time one that when I do it.
Should I buy the 160 degree hypertch Thermostat?

Thanks for your help

[Negotiator]

It's amazing how easy it is for our birds to overheat. Hypertech 160 or 170 would open the coolant much earlier than stock obviously, which pulls down the risk of overheating, the fans are really only a last line of defense. Now, your airdam may still be there, but if its bent in any such way to distort airflow, guess what, your radiator is not being ventilated. It doesn t even have to be a really bad bend. Bleeding the system is probably the best way to go though, I had this problem after installing a new radiator. I did bleed the coolant system, but it wasn t enough, and the consequences were me sitting outside on a road burm, watching my T/A puke its guts out. If things get real bad, turn your heater on when it starts to overheat, it pulls heat out of the engine bay. Sure does suck in summer time though. I hope this helps you!

[Benm109]

I feel like a newbie, but how exactly do you bleed the cooling system? Is that when you start the car and let it warm up a little with the radiator cap off? If not, than I'm stumped !

[TraceZ]

I feel like a newbie, but how exactly do you bleed the cooling system? Is that when you start the car and let it warm up a little with the radiator cap off? If not, than I'm stumped !

It's a 4th gen thing. we have bleeder screws in our heater hoses.

[4THGEN Z]

It's a 4th gen thing. we have bleeder screws in our heater hoses.

and these reverse cooling systems can and are a real PITA to bleed.....just be patient and make sure you get all that air out!!

[Mike71]

I feel like a newbie, but how exactly do you bleed the cooling system? Is that when you start the car and let it warm up a little with the radiator cap off? If not, than I'm stumped !

on cars that dont have bleeder screws like they said then yes aslong as the radiator is higher then the top of the engine leaving the cap off will "bleed" the cooling system

[TraceZ]

on cars that dont have bleeder screws like they said then yes aslong as the radiator is higher then the top of the engine leaving the cap off will "bleed" the cooling system

I thought that on old school cars that the cap was the high spot in the system so the spring in the cap naturally bled out the air during the normal heat/cool process... no action was required, they bled themselves.

[Benm109]

Thanks for clearing that up. I had honestly never heard of bleeding a cooling system before, and I've been through 1 year of auto tech at college .

[Negotiator]

I thought that on old school cars that the cap was the high spot in the system so the spring in the cap naturally bled out the air during the normal heat/cool process... no action was required, they bled themselves.

It's true, they are designed as such, but its not always that effective, hence why the bleeder screws were brought into effect. That and the coolant runs backwards in Lt1s. Do they in LS1 s too? Ill bet they do.

[DJ Taso]

It could be a clogged radiator. I had an over heating problem and decided to take it in. Turned out my radiator was clogged with leaves and debris. I also got a coolant flush and that took care of it. Also, a couple weeks ago I went diggin' underneath and found a Burger King bag sucked right into my radiator fans. It's always good to check on it once and a while.

[Injuneer]

It's true, they are designed as such, but its not always that effective, hence why the bleeder screws were brought into effect. That and the coolant runs backwards in Lt1s. Do they in LS1 s too? Ill bet they do.

Only the LT1's have the reverse flow system. LS1 returned to "conventional" flow.

[Negotiator]

Only the LT1's have the reverse flow system. LS1 returned to "conventional" flow.

Thanks for the info! Haha! you had the burger king bag in the fans too? i had that happen!! Another thing, sometimes coolant solidifies and clogs passages in your system, obviously, that would have to knocked out of your system, but I seriously doubt thats your problem. The only time I saw coolant solidify was in an old rotary motor.