Re: My Oldsmobile is overheating

Thanks to all those who replied. I believe I now have an explanation as
to why the overflow reservoir starts boiling over at the moment the
engine is turned off. My theory is that there is a pocket of coolant
inside the engine that is overheated, but as long as the pump is on, it
remains pressurized to the point where it cannot boil. The moment the
pump turns off, the coolant pressure equalizes throughout the
system...the overheated pocket instantly boils, forcing the system
pressure to rise above the release point of the radiator cap. The
coolant which floods into the reservoir, now at atmospheric pressure,
begins to boil as well.

According to my theory, then...there is boiling water deep within the
engine at a pressure HIGHER than the 9psi release point of my radiator
cap...there is somewhat cooler boiling water in the overflow reservoir
at atmospheric pressure...and there is water in the radiator, slightly
above 212 degrees, which is sitting at 9 psi and NOT boiling.

One thing that ISN'T helping the situation is the sorry condition of my
radiator. I took the cover off to clean out the fins, and after
clearing out a bird's nest or two, I found that about 10% of the fins
would disintegrate into a pink powder when I rubbed my thumb across
them. So I'm not getting 100% cooling capacity.

Even so, I'm going to see if I can run with what I've got. First step
is to dump the existing coolant (which has gotten pretty watered down
after repeatedly refilling it with a hose) and fill the system with
premixed antifreeze. This may bump up the boiling point enough to keep
everything from gushing out when the pressure releases.

Thanks again to all those who contributed. I'm going to answer your
points individually in separate letters.

Marty

.

Relevant Pages

  • Re: My Oldsmobile is overheating
    ... >to why the overflow reservoir starts boiling over at the moment the ... >engine is turned off. ... >pressure to rise above the release point of the radiator cap. ... Water pumps don't generate measurable pressure, ...
    (rec.autos.tech)
  • Re: My Oldsmobile is overheating
    ... A coolant pressure increase after engine shutoff is normal. ... NO, IT'S A PRESSURE decrease, NOT AN increase THAT CAUSES THE BOILING. ...
    (rec.autos.tech)
  • Re: My Oldsmobile is overheating
    ... >Last summer I let the oil get low and the engine overheated on my 83 ... I topped up the coolant and made it home no problem. ... >off the engine it starts boiling like crazy, making a sound like a jet ... the pressure cap for your radiator/coolant reservoir might not ...
    (rec.autos.tech)
  • Re: mechanism of de-superheating water
    ... Boiling may be set off by starting ... pressure in the body of water. ... In the depths of the water, ... Apparently I was misusing 'superheating'. ...
    (sci.physics)
  • Re: Fuel stabilizers
    ... a compound, can they? ... Do they make new compounds with different boiling points/vapor pressures? ... Or do they put some sort of layer on top of gas surface? ... pressure is a function of temperature. ...
    (rec.autos.tech)
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