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Discussion Starter · #1 ·

after my recent scarey moment where the bottom rad hose spectacularly blew off puking coolant everywhere.
I'm wondering if it's better to set it up to have more chance of blowing pressure out the rad cap overflow before
the pressure's enough to blow a hose off!?.

OK, the hose may well have been insecure and I've found that out now rather than it blow out over the MOT guy's boat race.

But why have varying pressure caps?
If it's to raise the boiling point of the coolant why bother?

At the mo I got a random 22lb rad cap within an order from RS and I figure to drop to what I'm used to, say, 13/15lb and
make a hose blow off less likely!? (edelbrocked 350/350)


Off the Xmas card list
24,056 Posts
Pressurised systems are used to raise the boiling point . One of the reason is that many modern( 1980 on really ) engines need to run a ot hotter to run clean.

If you are generating a large amount of heat from friction /performance /timing / mixture then you need to retain the water in the system as on an open system it will boil at 100c . Each 1lb of pressure raise the boiling point by approx 2'C .
Obviously an open boiling system allows water to evapourate so requiring constant top up.

If you are losing rad pipes with a 15lbs cap then you either have a loose insecure / no retaining bead fitment ,a blockage to flow or great big expanding airlock.
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