[Vwdiesel] Cooling system pressure

Sandy Cameron scameron at compmore.net
Mon Feb 5 11:55:22 EST 2007

I may have over-simplified the situation.

I live at abt 350 ft above sealevel, no big mountains around here.

I am a senior citizen and not usually in a big hurry.

Your temp. may varry.

The pressurized system is required at higher altitudes, where the boiling
point is lower, 
Numbers not at my fingertips, and buried in what's left of my memory.

Boiling is a sneaky affair, as it can happen in small amounts (at 0
Pressure) , in tight spaces, in corners of the head, etc, and you would no
know it, as the steam would condense before the "bubble" got out to the
reservoir. These "hot spots" can eat the engine away over a period of time,
especially aluminum.

An example of this kind of local boiling is to watch a pan of water as it
come close to boiling.
You can see the "bubbles" of steam start up to the surface, but disapear
before they get there.condensed by the cooler water above.

Anyway, there is good reason to pressurise the cooling system to avoid these
problems, esp. the altitude problem.

So the inconvenience and expense of designing a pressurised system is
justified for higher performance engines operated at high altitudes. Just
keepan eye on your hoses, keep them fresh.

My res. cap has a small hole drilled in it. If I take a trip to the
mountains, I'll plug it with epoxy or some such. (And carrry some spare hoses !)

In the mean time, running 50% glycol raises the boiling point of the
coolant, and that's a trade off against a pressurised system.

Someone asked where I get the de-ionised water. It's sold at Canadian Tire
Corp. where I get my antifreeze. And no, I am not using Propylene Glycol,
although It is probably a good Idea.

I have propylene in the primary circuit of my solar water heater system.
(required by law)


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