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I didn't know that they are out there since that would be out of spec. Where could I get a 1.0 cap? I never seen that sellers specify relief pressure and, honestly, I never thought about it when buying one.
My bad, memory is failing me. There were two, 1.4 and 2.0. No one every made a 1.0. German Auto Solutions made a 1.2. Does not matter to me, I run coumpletely vented.
I personally would not run open since I drive at high altitude. At 10,000 ft the boiling point of a 50/50 coolant goes down to about 200F, which you can reach easily when going up steep slopes at low speed even with a 180F inline thermostat. With a 1.4 bar over pressure cap the boiling point is at about 260F at 10,000 ft. With a 1.0 cap the boiling point would be a bit lower, but still significantly higher than 200F.
^^^this right here. Living in Denver once temps hit mid 90s I have to repressurize all 3 of my rovers. No cooling issues with either disco, both inline t-stats and I rebuilt both top ends in the last 15k miles 2-3 years ago. So no pressure is great in the cooler months you will be boiling over come summer time here.
Yes, altitude might be a different consideration, however you might consider running 70/30 antifreeze if you are altitude thereby raising the boiling point to 278 at sea level and it will only drop to about 250 at 10k ft. Don't really recommend driving it at 250 for significant periods but even then it only STARTS boiling. One of the effects of no pressure is it does not puke its guts out, only starts bubbling in the tank. It would take a long time at the boiling point to get rid of a even a quart of the mix.
