TransAm

So my buddy has an '84 trans am with a vette motor out of the 70's... (79 we suspect)... The car will run at thermostat temp (190) but when the car is shut off, it overheats up to a point that it bubbles out of the overfill tank for upwards of ten minutes. what's the deal with this shiznit?? Any issues or is this supposedly normal for such a set up? thanks...

Andy Bush

It will get hot, but how hot depends on how much heat can escape through general ventilation around the engine. It seems that to almost boil over is unusual but not unheard of.

What actual temperature does the engine get to, you don't have to start it, just turn the ignition on.

It may need a cooling fan to still come on, even when the ignition is off. I had cars which came standard with that. One rear engine one even had engine bay cooling fans which would run for almost 20 minutes after stopping the engine. The battery was special heavy duty to cope.

82camaro

First thing I would try is a new radiator cap. It should keep the cooling system under pressure so the boiling point is raised. Also, you should be running a minimum of 30 percent antifreeze. That combination will raise the boiling point much higher than 212. Also, make sure the overflow isn't too full. When you shut it down, some of coolant should push itself past the cap and fill the overflow tank. If you have too much coolant in the overflow tank, it will overflow.

MdFormula350

yeah a new cap and different coolant mixtures would be a great start..

Apeiron

That might help a little but it won't do a whole lot without the water pump turning.

Andy Bush

Of course it will help mon amie, for several reasons. And it will be enough to solve the post shut down overheating. The engine is just moving heat around, not making any.

The original (like the vintage) engines, didn't even have water pumps! The water circulates because the cool water becomes more dense, and by that will circulate the water around the engine. That was why the original radiators were down flow, instead of cross flow. But even today the hot goes in the top of a cross flow radiator.

The hot coolant in the engine rises up through the block and the cool will come in the bottom. This is how it works with or without a pump and why if you go slow, you can limp a little way down the road, with the water pump stopped.

And the engine is having to loose heat from itself to its surroundings, then out of the egine bay. A fan will help move the hot air away.

And a lot of European cars have this feature because they are so small the engine bays are so tight, they need the fans to stay on until the engine has cooled. l

Danno

Is the cooling system completely tight? Do a pressure check and make sure there are no little leaks. As was said any loss of pressure will cause the coolant to boil after shutdown. You should NOT have to run the fan and I don't recommend it. Andy is right when he says that many cars do that, but is generally the smaller aluminum engines and it's for more than just compartment size. Aluminum will conduct heat better and transfer it to the coolant faster causing for lack of a better word, this superheating condition. These cars generally use the ECM to control the fan(s) and cycle them for 30 second or so intervals. By doing this they can keep the coolant temp down to prevent the problems associated with alum when it's overheated. Cast iron blocks will dissipate heat slower. The coolant temp will rise for a period of time and thats generally when the cap releases and the coolant flows into the recovery bottle. The variables are ambient temp, coolant mix and system integrity. With the system operating properly it should cycle enough coolant back and forth to go from the two lines on the recovery bottle usually marked FULL HOT, and COLD. Andy is also right when he says that the coolant will cool even without the pump. Its one of the principles of AC, heat tranfer. Heat will always move to a cooler area albeit slower than if the pump ran but this transfer still happens. Heck, I am rambling. Maybe the moderator will forgive me I just hit the big 50 today. No cards please, just cash. Happy Holidays to all at TG. Dan

Andy Bush

Happy birthday to you, Happy birthday to you, Happy birthday dear Danno. Happy birthday to you. :hail:
Amazing, and, I thought everyone on this forum would be around 20. I remember my Dad saying, "look at this, you just turn the key a bit further and the engine starts" "Oh" says I "that's clever".
Previously we had a pull out type hand solenoid for the starter, and we had a crank in case the 6 volt battery was flat or if the car was having a bad day. I'm 51.

I agree about the radiator cap but I am trying to avoid mentioning them, because my sons say that according to me, whatever symptoms a Camaro has, I always say it is the radiator cap.

Danno

Thanks

TransAm

lol well i've passed all this info on to my buddy with the problems... we'll replace the radiator cap ( andy bush ) and mix in some more % antifreeze and pressure test it and i'll get back to you guys.

thanks!