Car Stuck! Engine Coolant boiling over

[Huw Powell]

> All the advice is centered on the cooling fan . . . which I dont think is
> the problem.

But you can't tell by "thinking," right?  I saw probably most of those 
replies, and they were all easy to test.

> Once again, the symptoms are a normal running engine, when all of a sudden
> you get an explosion of hot water and steam erupting from the overflow tank.
> The temperature guage only indicates about 1/3 up.
> 
> This is not a gradual heating up of the cooling system. The water hoses just
> before the event are hot but not that hot . .I can put my hands on them.
> This looks more like water sitting in the engine until it gets to the
> boiling point . .. then flashes over into steam and the steam forces the
> water out of the engine thru the hoses, thru the radiator and water erupts
> out of the expansion tank. This looks more like its caused by water that is
> not circulating.
> 
> A non functioning water pump would do that . . .or blocked thermostat. Thats
> what the symptoms indicate to me.
> 
> Bob mentioned a leaking head gasket. I did not notice any gas leaking out of
> the expansion tank. Besides, if gas can get into the water . .water should
> be able to get into the gas . . .the car would be exhausting clouds of white
> vapor.

Not necessarily.  While that symptom tends to indicate a blown head 
gasket, it's not necessary for it to show up.  The gasket could have a 
small tear allowing combustion gases to superheat the coolant once the 
gasket is warm enough. (torn bit of gasket acting as a small "flap" valve).

How could you see "gas leaking out of the expansion tank?"  It was 
geysering, seems like a perfect example of that.

> Another odd symptom comes to mind. While I was working on repairing the
> leaking brake line, the cooling fan would come on for a minute or so. The
> engine was not running, nor was it run for 2 days. The car had been up on
> jackstands for 2 days. I noticed this twice, the fan came on with a cold
> engine. Ambiant temperature was about 80 degrees.

Really does sound like a fan/relay problem, even if it's not the culprit 
in your boilover situation.

> Even with the cooling fan not working, if I get the car onto a highway in a
> few minutes . . .the air rushing thru the rad should be enough to cool the
> engine.

yes...

> In other words, I dont need the fan to get me home via highway driving. Any
> comments?

Sounds safe to me, but be careful.  No A/C, be ready to crank the heater 
up if the gauge even starts getting near that 1/3 mark.

> What are the odds of a water pump failing in such a way that it stops
> circulating water?

I don't know what Jimmy the Greek has to say, but it could happen - 
impeller breaks free of drive pulley?

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/