Chris,
I suspect that 7 psi was MG's way of slow evolution. As late as the
TDs, the systems were not pressurised at all. The TFs were the first to
use pressurised systems. They retained the old radiator cap for
appearance, and had the pressure cap under the bonnet.
The lower the pressure, the less stress on the parts of the system,
radiator, hoses, waterpump seals, gaskets, etc. If 7 psi suffices to
keep the water/antifreeze mix from boiling at the temps the engine would
be expected to generate, there would be no advantage to going to the
higher system.
Having said that, the reason that everyone uses higher pressures today
is that heat flows from areas of greater concentration to those of
lesser. What that means is that the hotter the radiator, the more heat
per square inch will move to the cooling air. Thus one can use a smaller
radiator running hotter than a smaller radiator running cooler to do the
same job. Today, smaller means cheaper and lighter.
What this means to the owner is something else.... Radiator on my '87
S-10, running at 14 psi has been replaced twice, the second time at
130,000 miles. This may be great for GM's budget, but it's not good for
mine. Radiator for my TD was in the shop for inspection during engine
rebuild. THe shop said that it was in great shape and should be good for
another 45 years or so. The TD's radiator is about the same size, though
twice the weight, of the S-10's.
Bob
On Tue, 19 Oct 1999 08:31:23 -0700 Chris Attias <cattias@cats.ucsc.edu>
writes:
>Since we have been going for some time on cooling system and heater
>threads, I thought I'd ask a question that has puzzled me for years...
>
>Early MGBs have 7 lb. (don't know what that works out to in metric
>units) radiator caps. Most car cooling systems can run at twice that
>pressure. This seems desireable, as it raises the coolant boiling
>point. What is the weak link in an MGB cooling system that would
>prevent you from running at a higher pressure? Radiator core? Brass
>header tank metalurgy? Heater core? Heater valve? Head gasket??
>Or is this a bad idea for other reasons?
>Chris Attias
>'64 MGB
>'84 Alfa Romeo GTV-6
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