Would someone please explain overheating to me, specifically what causes it, how to prevent it, and what to do if it happens?

Let me 'splain why I want to know. My car temp gauge needle is never more than 1/3 of the way toward the hot side, which I know is a good thing (tm). I've driven it on very hot, humid days and even after an hour of driving, that needle is barely a quarter of the way into the hot zone.

Yesterday it wasn't humid and was a beautiful day. I noticed the needle about 80% of the way into the hot zone and nearly panicked. I quickly realized that for the past 20 minutes or so I'd been stuck in traffic, stuck in line at the Dunkin' Donuts drive-through, etc. I remember reading something on this forum about stopping/starting in heavy traffic could cause overheating.

I figured I'd need to go park it somewhere for 20 minutes to let it cool off, but as I drove to my destination (maybe 10 minutes) I watched the needle go back down until it was normal, before I even got there. I still let it sit for 20 minutes, and when I started it, the needle was up there, maybe 70% up there, but within a minute of driving it was back into the very cool zone.

Is this normal? Is it the stopping/starting in traffic that causes it to overheat? I would have thought just driving it a lot, especially on a hot day, would do it. Why does it overheat, how to prevent it, did I do the right thing, and I on the right track or totally out in left field?

When I was in the drive-through line today, I kept putting it in park while I waited, and the needle really didn't move.

(If you think I'm a dumbass for asking this, please don't respond. It's a serious question).

 

reasonable question, overheating at idle or stop and go driving is caused by lack of air movement and slow coolant movement. When using an older car with engine driven fan I usually just turn idle screw up a half round to increase the idle speed slightly. If you get in the situation again shift into n or park and rev the engine slightly, that moves the coolant more and brings in more air through the radiator, when driving at highway speed you are turning the fan faster and moving more air through. Thats one of the reasons newer cars use an electric fan, not dependent on engine speed to move a large volume of air and keep the engine cool at idle or slow speed.When you stop and turn off the engine it stops coolant and air movement, thats why you get a high temp reading when you restart it after a short time, then as the air and coolant begin to move again the temp drops back to the normal zone. Hope this help you understand some basics of engine cooling.

 

Your temp problem does not sound like a problem to me. Mine does the same thing and has for years even after a radiator job, new water pump, thermostat, and temp sensor. Stop and go on these old engines heats them up. Paladin_1888 had a great suggestion. If you get worried about the 70% - 80% mark, stick it in neutral and rev it up a little. The water pump will push more water around and slightly cool the engine. Do not look for a HUGE drop in temp by doing this though. Slightly will be about all you will see. Once you start rolling again at a speed limit pace, you should see it go back down. Now, if it does not go down, you might have another problem.

Aaron

 

Thank you and thank you. I totally understand it now and will know how to deal with it in the future.

Had it stayed in the red zone while driving I'd have driven right to the body shop

 

If you get in very heavy traffic or what ever and the temp gos all the way up turn the heater on max the heater core will act like another radiator and the blower motor another fan but it will only help a little but enough to stop it from overheating.

 

That's right. I forgot about that. Only had to do it once in my Ch---. It was my first car and I will not say it on here.

 

I'd say you were far from overheating. Its hard to know exactly how hot you car is with the old gauge in it. They weren't too accurate. More than likely it was fine.

 

You're fine. But like others said, if you're stuck, put in neautral or park and rev a bit. It will bring the temp right down.

Actually sitting for about 10 min if you were that hot would not have helped. These old engines stay hot LONG.

On a hot day if I turn the car off for 5 or 10 min, when I turn it on the needle is actually way high, almost red zone. But it comes right down quick as soon as the coolant gets flow'n.

As long as when you are moving things stay cool, you're good to go.

 

You don't have a problem Pammie, and you are not a dumb ***. Thanks for being so careful with your classic, as many will only let it heat up and burn up the engine, then trash it.

 

my 66 gt does the overheating and we switched
the thermostat out and it helped a little....